TD5 Airconditioner efficiency.

[Captain_Rightfoot]

My AC compressor failed recently. The recommended AC place fitted a new compressor (and tx valve), but it's still woeful... possibly not as good as before which wasn't great either. This has been a constant issue with this car. I did some testing after the new compressor.

19 apr. 1330. Bom 27.6 deg
80-100k middle fan 10-11 degrees Celcius
Town speeds 12-14 degrees Celcius
Extended idle 15.8 degrees Celcius
My Lap 35.

Given it's not really able to keep up even on a moderate day, I really would like this to perform a bit better. Like at that level of efficacy it's almost better just to open the windows.

Has anyone else had any success at making this system at least work well enough to get the air coming out of the system is at least typical AC temps of like 4?

New better condenser and and fans are my only ideas as I know changing the evaporator would be challenging.

[shack]

Just to clarify, it's in a defender?

If so, late or early?

The systems are very different to each other.

I have both styles, I've done a lot of work on it and I've got the late one working frosty cold.

The other is not currently going.

[Captain_Rightfoot]

Just to clarify, it's in a defender?

If so, late or early?

The systems are very different to each other.

I have both styles, I've done a lot of work on it and I've got the late one working frosty cold.

The other is not currently going.
Mine is a 2005 english built Defender TD5. It's a 110 so small air conditioner in a large white box.

It's got the locally attached under dash AC.

EDIT: This mornings revelation that despite having a new compressor the condenser fan was not working. "I know we checked that". Yep.. but it's not working now.

[shack]

Mine is a 2005 english built Defender TD5. It's a 110 so small air conditioner in a large white box.

It's got the locally attached under dash AC.

EDIT: This mornings revelation that despite having a new compressor the condenser fan was not working. "I know we checked that". Yep.. but it's not working now.The condenser fan only works under certain conditions, I can't remember what they are off the top of my head.

It's a mixture of ambient temp, road speed and coolant temp, or something along those lines.

If the weather is cool it may not come on, that's likely the car with yours.

Does yours have 2 4 position switches to control the fan and AC temp?

[Captain_Rightfoot]

The condenser fan only works under certain conditions, I can't remember what they are off the top of my head.

It's a mixture of ambient temp, road speed and coolant temp, or something along those lines.

If the weather is cool it may not come on, that's likely the car with yours.

Does yours have 2 4 position switches to control the fan and AC temp?

Re the fan.. that was the update .. apparently it is working when it wants to work.

Yep, mine has the two switches. 0-3 fan and 0-3 AC.

[shack]

Re the fan.. that was the update .. apparently it is working when it wants to work.

Yep, mine has the two switches. 0-3 fan and 0-3 AC.So the condenser fan is working properly?


If you have the 2 4 position switches, you will also have a separate AC ECU.

Do you have a Nanocom?

[shack]

I had a quick look for some info.

Unfortunately there is very little available on the AC system and ECU used in late TD5 defenders, so I'll give some D2 numbers for the HVAC ECU and hopefully they are at least similar.

For cooling when the AC is on in the D2, the condenser fan turns on when roadspeed is under 80kmh and ambient temp is over 28°c, it turns back off when roadspeed increases to 100kmh or ambient drops to 25°c.

I don't know if both figures need to be achieved for switching or not, but that gives you some info to work with.

It also serves to help with engine cooling when of the AC is off, but I won't get into those figures here.

I know I've lowered the operating switching temps on mine as I felt it was better to start cooling earlier.

[Captain_Rightfoot]

So the condenser fan is working properly?


If you have the 2 4 position switches, you will also have a separate AC ECU.

Do you have a Nanocom?

I do have a nanocom but it's gen 1 and basically useless so let's say no.

I'm not aware of a second ecu.

[Captain_Rightfoot]

I had a quick look for some info.

Unfortunately there is very little available on the AC system and ECU used in late TD5 defenders, so I'll give some D2 numbers for the HVAC ECU and hopefully they are at least similar.

For cooling when the AC is on in the D2, the condenser fan turns on when roadspeed is under 80kmh and ambient temp is over 28°c, it turns back off when roadspeed increases to 100kmh or ambient drops to 25°c.

I don't know if both figures need to be achieved for switching or not, but that gives you some info to work with.

It also serves to help with engine cooling when of the AC is off, but I won't get into those figures here.

I know I've lowered the operating switching temps on mine as I felt it was better to start cooling earlier.
As can be seen by my testing the other day - I'm seeing temps at 15 at the vent for extended idling on a warm day.

Can't we do better than that? I'm thinking I need to investigate a second fan that runs far more. maybe any time the ac is switched on.

[shack]

The second ECU is behind the right hand side speaker and the AC controls.

I strongly doubt your issue is the condenser fan capacity.

If you are handy on the tools I've got a mod you could try for testing purposes.

[prelude]

I have been building an AC recently and I have found a lot of things.

There is a relationship between pressure and temperature for instance, in the case of r134 look at this table:
https://benegas.com/wp-content/uploads/2020/09/R_134a_dampdruk-tabel.pdf

Most compressors can only do so much difference and ambient temperature does play a role. So on a hot day, with a hot engine (radiator radiating into the condenser) the pressure and thus temperature up front needs to be quite high and most condenser fans are not capable of cooling the entire thing. I know it isn't on a P38 for instance but the viscous fan does help something.

If you can reach it (watch the fans) measure the temperature of the condenser when extended idle. Also check the evaporator temp (the actual evaporator of you can reach it, not the outgoing air but it would be close enough)

Let's see if we can diagnose this :)

Cheers,
-P

[Discofender]

Watching this thread with interest. After recently fitting a new compressor and condenser to my D2a, I'm now enjoying icy polar blasts and am wondering what can be done to my '04 Defender's poor excuse for aircon.

[Captain_Rightfoot]

So I don't have the car back. I might not get it back until next week. :o

The fist thing I was going to try was to sit it idling and see if we see 15 degrees inside temps again, and then hose the condenser and see if that drops the temps. That way testing the effect of cooling the condenser?

The problem I'm running into is winter seems to be finally on the way in BNE. It's cool this morning. 15 degrees :o

[shack]

and then hose the condenser and see if that drops the temps. That way testing the effect of cooling the condenser?



That's the old school way of doing it and it should isolate the issue to some degree.

What were the ambient temps when you were seeing 15° at the vents?

[prelude]

I am not sure if any of the other land rover AC figures are going to be useful for the defender (old style) since they are somewhat unique in that they were never designed to have proper heating or cooling :) I believe that is before that lasts style dashboard right?

Also, I would not be convinced the condenser fan(s) is/are enough. On the P38 there are two I think 12" fans to assist the belt driven fan and I have tested them stand alone (I converted to an electric compressor so can run it without the engine running) and they are barely able to keep up with a MUCH smaller capacity compressor.

A bit of AC background for those who are interested:

There should of course be a temp drop over the condenser but not necessarily the way you'd expect. An A/C works on pressure difference Make the outside hot so the inside can be cool. The hotter it is outside (ambient), the hotter the condenser needs to get to be able to transfer heat into the air. A rule of thumb for a bit of an efficient transfer is that you'd need around 15c difference.

The way an A/C creates that pressure is not just by compressing the gas into the condenser, but by vacuuming the evaporator. Most systems use a so called expansion valve that regulates this pressure and tries to keep the pressure difference as large as possible. Also, most compressors have an upper pressure limit to which they can operate which is regulated by a number of pressure switches. These basically regulate the compressor to operate and the condenser fan(s) to kick in or not (via the ECU I read a while back in this thread it seems)

So, if at idle your temps are not great the first suspect would simply be compressor RPM. The compressor simply does not work hard enough to compress the gas, create a pressure difference that is sufficient and thus fairly high cabin air temps. The way to test this would be to turn the blower to its lowest setting so that airflow over the evaporator is minimal and see if the temps drop. It would simply be the case that the bit of cold the compressor can provide is simply not enough and the strong / warm airflow heats up the evaporator too fast, hence the not-so-cold air you measure. Compressors do wear over time so it can be the case that it has gotten less enthusiastic in its compressing duties.

The second suspect would be the condenser and its fan. When driving a huge amount of air passes it facilitating cooling. If the condenser is in less than perfect nick (missing vanes, corroded, plugged with dirt) it will quickly diminish in cooling capacity and in almost all cases in older designs the thermofan(s) that aid in cooling are just not up to the task to carry away enough heat. One way to test that would be to see if the fan is blowing non stop and if the condenser gets real hot AND possibly if the compressor kicks in and out.

Hosing down the condenser with cold water would certainly help in testing since water can carry away much much more heat than air can.

For diagnostic purposes, there are only a couple of reasons a compressor turns on or off on a belt driven system:


pressure too low, this happens when the system has a leak or whatever and there is not enough gas. It would never work
pressure too high, the pressure in the system on the high side (condenser) is beyond spec, often 20-30 bar depending on the setup, compressor, etc. (ie. between 70-90c condenser temp roughly)
evaporator too cold (freezing). When the evaporator freezes the system wont work properly anymore and thus it needs the compressor to stop (Honda uses around 0c, my P38 range rover stops at 4c. In any case COLD)


The third suspect could be a worn/broken TX valve. It simply lets a tad bit too much gas pass and at idle the compressor is not working hard enough to keep that up and you get "lazy" cooling. This is not something that is easy to test, I reckon keeping the car parked but opening up the throttle for an extended period of time (so minutes, not seconds) to say cruising speed RPM and see if that fixes the AC cooling issue. Not sure if the TD5 had a belt driven fan, I guess it does? so that also means airflow through the condenser would go up so keep that in mind but the hose test would probably already have taken care of that.

Most AC shops with one of them fancy filling units with dials and all that can easily test all of this.

Emulating high ambient temps for testing though, not sure how to do that :) Maybe you'll get another few hot days!

Cheers,
-P

[Captain_Rightfoot]

That's the old school way of doing it and it should isolate the issue to some degree.

What were the ambient temps when you were seeing 15° at the vents?
It was 27.6 according to BOM at that time. The 15Deg was for extended idling.

[Captain_Rightfoot]

I am not sure if any of the other land rover AC figures are going to be useful for the defender (old style) since they are somewhat unique in that they were never designed to have proper heating or cooling :) I believe that is before that lasts style dashboard right?

Also, I would not be convinced the condenser fan(s) is/are enough. On the P38 there are two I think 12" fans to assist the belt driven fan and I have tested them stand alone (I converted to an electric compressor so can run it without the engine running) and they are barely able to keep up with a MUCH smaller capacity compressor.

A bit of AC background for those who are interested:

There should of course be a temp drop over the condenser but not necessarily the way you'd expect. An A/C works on pressure difference Make the outside hot so the inside can be cool. The hotter it is outside (ambient), the hotter the condenser needs to get to be able to transfer heat into the air. A rule of thumb for a bit of an efficient transfer is that you'd need around 15c difference.

The way an A/C creates that pressure is not just by compressing the gas into the condenser, but by vacuuming the evaporator. Most systems use a so called expansion valve that regulates this pressure and tries to keep the pressure difference as large as possible. Also, most compressors have an upper pressure limit to which they can operate which is regulated by a number of pressure switches. These basically regulate the compressor to operate and the condenser fan(s) to kick in or not (via the ECU I read a while back in this thread it seems)

So, if at idle your temps are not great the first suspect would simply be compressor RPM. The compressor simply does not work hard enough to compress the gas, create a pressure difference that is sufficient and thus fairly high cabin air temps. The way to test this would be to turn the blower to its lowest setting so that airflow over the evaporator is minimal and see if the temps drop. It would simply be the case that the bit of cold the compressor can provide is simply not enough and the strong / warm airflow heats up the evaporator too fast, hence the not-so-cold air you measure. Compressors do wear over time so it can be the case that it has gotten less enthusiastic in its compressing duties.

The second suspect would be the condenser and its fan. When driving a huge amount of air passes it facilitating cooling. If the condenser is in less than perfect nick (missing vanes, corroded, plugged with dirt) it will quickly diminish in cooling capacity and in almost all cases in older designs the thermofan(s) that aid in cooling are just not up to the task to carry away enough heat. One way to test that would be to see if the fan is blowing non stop and if the condenser gets real hot AND possibly if the compressor kicks in and out.

Hosing down the condenser with cold water would certainly help in testing since water can carry away much much more heat than air can.

For diagnostic purposes, there are only a couple of reasons a compressor turns on or off on a belt driven system:


pressure too low, this happens when the system has a leak or whatever and there is not enough gas. It would never work
pressure too high, the pressure in the system on the high side (condenser) is beyond spec, often 20-30 bar depending on the setup, compressor, etc. (ie. between 70-90c condenser temp roughly)
evaporator too cold (freezing). When the evaporator freezes the system wont work properly anymore and thus it needs the compressor to stop (Honda uses around 0c, my P38 range rover stops at 4c. In any case COLD)


The third suspect could be a worn/broken TX valve. It simply lets a tad bit too much gas pass and at idle the compressor is not working hard enough to keep that up and you get "lazy" cooling. This is not something that is easy to test, I reckon keeping the car parked but opening up the throttle for an extended period of time (so minutes, not seconds) to say cruising speed RPM and see if that fixes the AC cooling issue. Not sure if the TD5 had a belt driven fan, I guess it does? so that also means airflow through the condenser would go up so keep that in mind but the hose test would probably already have taken care of that.

Most AC shops with one of them fancy filling units with dials and all that can easily test all of this.

Emulating high ambient temps for testing though, not sure how to do that :) Maybe you'll get another few hot days!

Cheers,
-P
Thank you for this post. Lots there.

The factory compressor failed at 180k. The AC shop replaced the compressor and the TX valve so both are new. I offered to get a denso compressor but the shop wanted to use their supply channels which was a Chinese compressor. I'm not sure whether a smaller pulley can be fitted but I doubt it.

The condenser is the factory one. It looks in reasonable shape without any obvious trauma or blockages. The AC shop pointed out it's a serpentine condenser which are not known for efficiency.

[BradC]

Emulating high ambient temps for testing though, not sure how to do that :) Maybe you'll get another few hot days!

Reduce / stop the airflow through the condenser. A bit of cardboard over the front usually works.

[shack]

Thank you for this post. Lots there.

The factory compressor failed at 180k. The AC shop replaced the compressor and the TX valve so both are new. I offered to get a denso compressor but the shop wanted to use their supply channels which was a Chinese compressor. I'm not sure whether a smaller pulley can be fitted but I doubt it.

The condenser is the factory one. It looks in reasonable shape without any obvious trauma or blockages. The AC shop pointed out it's a serpentine condenser which are not known for efficiency.I think the late TD5 condenser is the same as the puma condenser, I think they are a parallel flow unit and very efficient.

I'm not sure on the early/EU2 style, they also didn't have a condenser fan or AC ECU that I'm aware of.

[shack]

It was 27.6 according to BOM at that time. The 15Deg was for extended idling.15° with 28°ambient is pretty poor, unacceptable I'd suggest, it may be a condenser cooling issue, it may be a lack of system pressure, it may be a faulty thermistor or ECU.

My ECU is faulty.

[shack]

If anyone reading this thread owns a late TD5 defender with poor AC and also owns a Nanocom, I can do a bit of a Diag tune to see what the system is doing.

Just contact me if you want to have a go.

Cheers
James

[Captain_Rightfoot]

If anyone reading this thread owns a late TD5 defender with poor AC and also owns a Nanocom, I can do a bit of a Diag tune to see what the system is doing.

Just contact me if you want to have a go.

Cheers
James
Where are you based? (broadly)

[shack]

Where are you based? (broadly)An hour from Port Augusta..

So that's S.A. in case you haven't heard of the port.

[Captain_Rightfoot]

An hour from Port Augusta..

So that's S.A. in case you haven't heard of the port.
Damn bit far away. :o

[Captain_Rightfoot]

Ok update from the AC shop. They have cleaned the evaporator and it's apparently sitting at 10 degrees when idling. This sounds much better than the 15 the other day.

He also said that spraying the condenser with water made it drop to 8 or so. He said the electric fan was still working sometimes. He thought replacing the main clutch fan would help as he said "you could stop it with your hand".

So my comments about this. I have td5spy and then engine doesn't seem to really get hot. When going up a big hill or something and temps get up you can hear it start to work and the engine doesn't get hot. I thing the highest I've ever seen it circa 105 and most of the time it's high 80's or low 90's. He wants to replace the clutch fan but I'm concerned as I don't think it will help.

I would like to find out why the "ecu" doesn't turn on the electric fan or what the parameters are. It seems as though condenser cooling is the main issue.

Can anyone with a td5 AC confirm.. does the electric ac fan work when prolonged idling?

[shack]

I covered this off partially before.

I need time to go through and check diagnostically what it does.

[Captain_Rightfoot]

I covered this off partially before.

I need time to go through and check diagnostically what it does.
So I drove home from the ac place. Stop start BNE traffic. It is cool.. about 22 deg.

The whole way home the ac was oscillating between 4.5 and 6.5. So cleaning the evaporator appears to have helped as I've never seen those temps before. I need to test on a warm day though.

The engine ran high 80's and got to 91 once.. so not really enough to even get the clutch fan going.

When i stopped at home the AC electric fan was not running.

The AC guy said the fan runs sometimes.. but he didn't really know what the trigger was for it to run.

[shack]

So I drove home from the ac place. Stop start BNE traffic. It is cool.. about 22 deg.

The whole way home the ac was oscillating between 4.5 and 6.5. So cleaning the evaporator appears to have helped as I've never seen those temps before. I need to test on a warm day though.

The engine ran high 80's and got to 91 once.. so not really enough to even get the clutch fan going.

When i stopped at home the AC electric fan was not running.

The AC guy said the fan runs sometimes.. but he didn't really know what the trigger was for it to run.I listed the D2 HVAC settings above, other than that I can't give any more info until I have time ...

I'm guessing the ECU in the defender provides similar operation.

[prelude]

Just to be clear: my experience is with a P38 NOT a TD5 but most components will be roughly the same, the compressor is even fairly comparable I believe.

Having said that; The clutch fan is usually not sufficient anyway during hot days. The airflow is simply insufficient to carry all that heat from the condenser. I can not be sure how the condenser is mounted on the TD5 but in most cases with our older model vehicles there is not one of those molded fancy pieces of plastic that fits everything snugly. Often there are gaps between the different components. Point in case, on my P38 (from the engine ie the fan looking forward) first comes the radiator, then a gap and a bunch of oil coolers, another gap and then the condenser. The gaps not only exist between the cores in the horizontal plane but also on the top/bottom/sides. These gaps represent a much easier air flow and heaps of efficiency of the fan are lost by these gaps.

The engineers solved this "minor" little issue by placing an electric fan (or two in my case) directly on the condenser. Push fans are usually 10% less efficient but at least they are mounted directly atop the condenser, not losing any efficiency due to all the leaks/gaps. Also, the fact that they block airflow is compensated for by the very powerful VC fan that will force enough air through when the engine is up to speed.

Having said all that, I do not know how the TD5 ECU works without looking through the RAVE manual of your vehicle (which I do not have) but AC gas has a 1:1relation between pressure and temperature. Most AC systems use a combination of both to operate. For instance, eveporator temp is measured but not the pressure and for the condenser the reverse is usually the case. My P38 (and a lot of other systems) use 3 pressure switches that sit close to or on top of the dryer or very close to it. These have a value in which they open up and a value where they close. They control 4 different states effectively: (I know 5 steps below but step two is "do nothing")



< 2.4 bar the pressure is too low, do not engage the AC compressor, usually means not enough gas in system
> 2.4 but < 17 bar all is well, keep trucking!
> 17 bar, things are getting warm turn the condenser fan on (setting low)
> 21 bar, we are not cooling enough, kick it into high gear
> 30 bar we shut of the compressor since the pressure is too high.


So, like I said, not sure how the TD5 handles this without some digging around but in general high pressure should kick the fan in. You can perform a rather easy test though I think. There must be a relay that operates the condenser fan. You could take a decent piece of wire (with that I mean diameter) crimp two spade connectors on it and create a shunt wire to replace the relay and simply allow the fan to blow full speed and see what that does with your evaporator temperatures, that way you can determine if the package is performing as desired.

Cheers,
-P

[shack]

After more research I've realised the first 2 paragraphs here are incorrect and will be addressed later in this thread.

Neither of the defender TD5 ECU's (main engine and AC) monitor system pressure when engaging the condenser fan, there is only a low/high pressure switch which is used for hard off/hard on switching of the compressor.

Later vehicles obviously do monitor pressure and adjust displacement valves and fans etc..

I can adjust the main engine ECU to control the condenser fan differently, but I'm not sure it will help in the above situation.

Other things to consider...the defender evaporator is situated just above the floor and has no intake filters at all, so they get filled with crud.

I've cleaned my evap and made filters to stop it happening again.

They don't have a variable displacement compressor. The early type defender condenser is serpentine and has no fan, the late is parallel flow and has a fan. The early has an old school thermostat, the late has a thermistor and ECU, I think the ECU's or thermistors commonly fail, how many I don't know, but I don't trust them.

The last couple days have been around 23-27° and I'm getting about -6°air blowing out of the unit, if it's humid the evaporator will freeze at these temps pretty quickly, I have made my own control setup so I can select what I want it to do.

[Captain_Rightfoot]

Neither of the defender TD5 ECU's (main engine and AC) monitor system pressure when engaging the condenser fan, there is only a low/high pressure switch which is used for hard off/hard on switching of the compressor.

Later vehicles obviously do monitor pressure and adjust displacement valves and fans etc..

I can adjust the main engine ECU to control the condenser fan differently, but I'm not sure it will help in the above situation.

Other things to consider...the defender evaporator is situated just above the floor and has no intake filters at all, so they get filled with crud.

I've cleaned my evap and made filters to stop it happening again.

They don't have a variable displacement compressor. The early type defender condenser is serpentine and has no fan, the late is parallel flow and has a fan. The early has an old school thermostat, the late has a thermistor and ECU, I think the ECU's or thermistors commonly fail, how many I don't know, but I don't trust them.

The last couple days have been around 23-27° and I'm getting about -6°air blowing out of the unit, if it's humid the evaporator will freeze at these temps pretty quickly, I have made my own control setup so I can select what I want it to do.
The problem I've had is when it's really hot - unless the air coming out of the AC is really cold it doesn't do stuff. It needs to work like an actual ac unit.

So after reading the manual there are two fuses in the cabin Fuse 28 (ac blower) and fuse 29 (ac compressor realay /cooling fan relay). They are problably ok but the two relays under the drivers seat relay #1 and #2 are just described in the manual as "a/c relay if fitted". I might have a little look at them. I've had #4 the main relay play up in the past and it was not pleasant. So I'm suspicious of those relays.

I've never seen the fan run although the AC guy said he's seen it run.

[shack]

The relay under the seat for the compressor often fails, the female terminals in the socket stretch over time and heat cycles.

The condenser fan will almost certainly NOT run all the time the AC is on, only when ambient conditions (including engine temp) and roadspeed triggers are reached.

If the ambient temp is under 30°and the car is stationary, it probably won't run.

Where I live, ambient temp can often be 40-43°, the fan will run all the time then.

But I need to check all of this!!

[Captain_Rightfoot]

The relay under the seat for the compressor often fails, the female terminals in the socket stretch over time and heat cycles.

The condenser fan will almost certainly NOT run all the time the AC is on, only when ambient conditions (including engine temp) and roadspeed triggers are reached.

If the ambient temp is under 30°and the car is stationary, it probably won't run.

Where I live, ambient temp can often be 40-43°, the fan will run all the time then.

But I need to check all of this!!

The loose terminals was what was wrong with the "main relay" which would cause the car to stop! I gave them a tweak and hasn't missed a beat since.

As to if the temp is less than 30 the fan won't run.. this is crazy! 28 is warm enough to want the ac to work! I wonder if this was done with half an eye on engine temps to stop the engine getting too low.

[prelude]

The engine can't really get too low, the thermostat would simply close. Also the condenser fan (see my post a while back) is by far not capable enough to cool the engine by itself (also see a long thread by keithy regarding thermofans). It is used in conjunction with the VC fan on the P38 and I reckon it might also be on the defender to help cool the engine during idle / stop and go traffic where the VC fan would simply not pull enough air on hot days through the radiator. The condenser fan is simply helping at that point but not by much.

Mind you 30c ambient outside temp is warm for us, but for the AC it is not that much work. The refrigerant only needs to be 15c higher to do a decent job transferring heat to the surrounding air and as you know, the VC fan would already be displacing a decent amount of air through the condenser at that point.

At 45c ambient, that's where the "fun" starts. For the condenser to transfer its heat properly, you would again want a 15c difference or there abouts which makes the bloody thing 60c and that means the compressor needs to work a lot harder. It also means the temperature of the air going into the engine radiator has been heated up quite a bit as well and needs to work that much harder.

Like I suggested, make a shunt (or jumper) cable now that you can find the condenser fan relay and jump the fan to see what the behaviour is when idle with the fan on constantly.

Shack also mentioned: no filters for the evaporator, that will limit its functioning quite drastically when dirt gets in. Perhaps you found the culprit? ;)

Cheers,
-P

[shack]

Here we go...

Apologies for my earlier post (no. 30).

I've had the post edited to point out my error for other users later on.

The defender TD5 - supposedly all models with "factory" air, will have an AC ECU located in the under dash bolt in unit, behind the drivers side speaker and AC controls.

This little unit performs a number of functions.

1. It interprets the resistance from the thermistor in the evaporator to provide 3 different temp settings and to prevent evaporator freezing.

2. It uses the signal from a "trinary" pressure switch to assess 3 things.

Firstly, whether system pressure is high enough for the compressor to engage - low pressure safety cut out.

Secondly whether system pressure is low enough for the compressor to engage - high pressure safety cut out.

And thirdly whether system pressure is high enough to request the condenser fan to be engaged.

It then passes all these requests to the engine ECU, as the engine ECU is the one that actually controls the compressor and the condenser fan.

On my vehicle, the condenser fan comes on @ 225psi and switches back off @ 188 psi, so that's 37psi hysteresis, that will be to prevent the fan from constantly switching on and off.

The system does NOT monitor vehicle speed or ambient temp AT ALL, all condenser fan operation for condenser cooling is based on pressure alone.


For comparison on a Discovery 2 (which I'm more familiar with as I've had them for years) condenser cooling fan operation is controlled by the ATC - Air temperature control ECU (aka HVAC).

The fan is switched on if vehicle speed is 80kmh or less while air temp is 28°c or more.

It switches back off if either vehicle speed increases to 100kmh or ambient air temp drops to 25°c or less.

The D2 ATC does NOT monitor system pressure at all for condenser fan operation, it only uses a 2 pin pressure switch to low pressure cut out and high pressure cut out.


This took a while to sort out so hopefully it's of use to everyone with a TD5 defender that has poor AC.

I'm running different condenser fan operation and different temp control as well, (override but keeping all safety monitoring in place) although I'm still looking to change that for better operation.

Without my mods, the unit routinely puts out 15° air, although I think my AC ECU is on the way out and may be causing this.

*Note, both vehicles also use the condenser fan for engine cooling once preset coolant temps are reached.

[Captain_Rightfoot]

Here we go...

Apologies for my earlier post (no. 30).

I've had the post edited to point out my error for other users later on.

The defender TD5 - supposedly all models with "factory" air, will have an AC ECU located in the under dash bolt in unit, behind the drivers side speaker and AC controls.

This little unit performs a number of functions.

1. It interprets the resistance from the thermistor in the evaporator to provide 3 different temp settings and to prevent evaporator freezing.

2. It uses the signal from a "trinary" pressure switch to assess 3 things.

Firstly, whether system pressure is high enough for the compressor to engage - low pressure safety cut out.

Secondly whether system pressure is low enough for the compressor to engage - high pressure safety cut out.

And thirdly whether system pressure is high enough to request the condenser fan to be engaged.

It then passes all these requests to the engine ECU, as the engine ECU is the one that actually controls the compressor and the condenser fan.

On my vehicle, the condenser fan comes on @ 225psi and switches back off @ 188 psi, so that's 37psi hysteresis, that will be to prevent the fan from constantly switching on and off.

The system does NOT monitor vehicle speed or ambient temp AT ALL, all condenser fan operation for condenser cooling is based on pressure alone.


For comparison on a Discovery 2 (which I'm more familiar with as I've had them for years) condenser cooling fan operation is controlled by the ATC - Air temperature control ECU (aka HVAC).

The fan is switched on if vehicle speed is 80kmh or less while air temp is 28°c or more.

It switches back off if either vehicle speed increases to 100kmh or ambient air temp drops to 25°c or less.

The D2 ATC does NOT monitor system pressure at all for condenser fan operation, it only uses a 2 pin pressure switch to low pressure cut out and high pressure cut out.


This took a while to sort out so hopefully it's of use to everyone with a TD5 defender that has poor AC.

I'm running different condenser fan operation and different temp control as well, (override but keeping all safety monitoring in place) although I'm still looking to change that for better operation.

Without my mods, the unit routinely puts out 15° air, although I think my AC ECU is on the way out and may be causing this.

*Note, both vehicles also use the condenser fan for engine cooling once preset coolant temps are reached.
I'd just like to thank you for putting all this together.. very useful.

[Captain_Rightfoot]

So the update is that after the evaporator clean the system is now working **much** better. I can't say for sure that they didn't tweak something else, but the effectiveness is very much improved.

On a 27 degree brisbane day it was running at between 4 and 6 degrees with the car moving (possibly the best result I can remember recording). When the vehicle was stopped in traffic it went up to 10-12. Again a good result by historical perspective.

When the car was stopped spraying the condenser with water resulted in an instant significant drop in the temps. I have not seen the fan run - however the AC shop claimed that they have seen it run. I think there is more to be done in this space. A lot of my usage is crawling over sand dunes often at low speeds in high temperatures. Would be great to get some improvements here.

For the moment then next stage is to fix the new fault. it's not the fan because the noise can be turned off and on with the ac switch independent of fan. :|]


https://youtu.be/wlhpBw-8hJ8'si=7PNtWTRfTogOQeLN

[prelude]

Great write-up shack! that means that the TD5 mostly works as the P38 system does.

The one thing I can not yet figure out is why the AC would put out 15c without the condenser fan running. The only reason I can imagine is that the compressor is simply not running fast enough at idle to provide sufficient amounts of gas ie. superheat as it is called I believe. This means that the gas evaporates inside the evaporator completely before it has passed all the way through and it can not absorb more heat from its surrounding, in other words can't cool enough.

Using the P38 once again as reference; a quick google search resulted in finding the same compressor for a number of landrover vehicles including the P38, disco 2, defender. The denso part is JPB101330 which is a 155cc unit usually. As far as I can remember it usually worked just fine in stop and go traffic also on hot days but it did cut out every now and then but I wrote that down to the BECM limiting current usage in the P38. The pulley ratio I am not entirely sure about but my guess is it is mostly the same across all the vehicles, maybe a bit bigger on diesel engines since they rev less.

The fact that you can cool the condenser and get colder air does suggest there is something to be gained by letting the condenser fan run perhaps. Still, the pressure is simply not high enough in the system to warrant that thing running. 225 psi is around 15 bar which sort of matches the P38's setting, in any case you can check the temperature of the condenser (on the hot side) to see where the pressure us roughly at: 225psi / 15 bar is around 56c so if you read a temperature lower than that, it makes sense the fan is not running.

Cheers,
-P

[BradC]

The one thing I can not yet figure out is why the AC would put out 15c without the condenser fan running. The only reason I can imagine is that the compressor is simply not running fast enough at idle to provide sufficient amounts of gas ie. superheat as it is called I believe.

It's simpler than that. Cooling is fundamentally proportional to mass flow of refrigerant. A compressor compresses gas. The lower the compression ratio the more efficient it is. So for a fixed rotation speed, the lower the condenser temperature the more gas the compressor will move.

It's also proportional to the temperature of the condensed liquid, although cooling the liquid to expansion temperature is a sensible cooling rather than latent so it's not a massive contributor.

Of course, running the compressor faster moves more mass.

So the cooler you can get the condenser, the more efficient the compressor and the more cooling.

[Captain_Rightfoot]

It's simpler than that. Cooling is fundamentally proportional to mass flow of refrigerant. A compressor compresses gas. The lower the compression ratio the more efficient it is. So for a fixed rotation speed, the lower the condenser temperature the more gas the compressor will move.

It's also proportional to the temperature of the condensed liquid, although cooling the liquid to expansion temperature is a sensible cooling rather than latent so it's not a massive contributor.

Of course, running the compressor faster moves more mass.

So the cooler you can get the condenser, the more efficient the compressor and the more cooling.
But if it doesn't spin fast enough at idle to get the fan to run it's never really going to get cold at low engine speeds. I'm going to have to test this to see if it actually runs. I know I need to do some testing. I can't wonder what they were thinking with the design...

[shack]

But if it doesn't spin fast enough at idle to get the fan to run it's never really going to get cold at low engine speeds.

If what doesn't spin fast enough?

[RANDLOVER]

If what doesn't spin fast enough?

I think he means the VC fan at idle.

[shack]

I think he means the VC fan at idle.Thanks

[shack]

So this is a pic of the "rarely heard of" and "never seen" Defender AC unit. It's called "Unit-Air conditioning".

Mine is faulty, I don't know why yet, I'm going to attempt to diagnose and repair it.

My first thought is it's one of the diodes, as the compressor will actually run even without the AC knob turned on.

If anyone with electronic experience has any suggestions, feel free to help out.

Cheers
Jameshttps://uploads.tapatalk-cdn.com/20250514/3afb8c78d5fd4aa408c46416d4244b71.jpg

[BradC]

Without the benefit of a wiring diagram or pretty much any context, I'd suggest if it drives the compressor then either the quad op-amp is faulty or one of the switching transistors (the one that drives the compressor) is shorted.

I will say being pretty basic it shouldn't be hard to track down the cause.

[shack]

Without the benefit of a wiring diagram or pretty much any context, I'd suggest if it drives the compressor then either the quad op-amp is faulty or one of the switching transistors (the one that drives the compressor) is shorted.

I will say being pretty basic it shouldn't be hard to track down the cause.Sometimes it works ok, sometimes it turns the compressor on and off with only half a second between cycles, sometimes it won't engage the compressor at all.

I can see the commands diagnostically and the engine ECU is doing what it's asked to.

I guess a faulty trinary switch could cause the no run situation.

I have all the wiring diagrams and will post when I have time.

The fact that it will SOMETIMES fire the compressor (via the engine ECU) even when the switch is off is the one that gets me... So a signal is getting through when it shouldn't.

But not all the time, it did it today and it did it once last month as well.

[shack]

The switching transistors can be tested?

Yes it is pretty basic, so I should be able to sort it, plus a new genuine one is about $500.. so that's a bit more incentive!


The condenser fan always works as expected, so maybe it is just the other circuit.

[shack]

I've tested the switching transistors.

Both are "BD139" but different brands.

NPN

E C B pinout

Red lead on base.

First transistor

B and C .705 volts

B and E .706 volts



Second transistor

B and C .666 volts

B and E .668 volts

[prelude]

Did you measure them removed from the pcb?

It does look extremely simple. I would not even call it a ECU since there is no microcontroller on it :) It looks more like a logic level converter into anything 12v that the higher power electrics in the car can work with. Should be easy to test signals/voltages over those chunky in/out pins.

But first, I'd look for dry solder joints before you hook it up and measure voltages across the pins (the lm324n datasheets are all over). The BD139 can not power the AC clutch on it's own, it is rated at 12watts max and 1 amp current so those transistors are only used to power relays. (these use typically around 200mA max) so that's why they run without heat sinks.

I reckon two of the more beefy diodes are there to protect the transistors from flyback of the relais coils. Easy to test those too.

Back to captain rightfoot :) The VC fan would likely not run fast enough at idle to cool the condenser when it's really hot. That's why the thermo should kick in eventually. Well, if you've done some testing we'll debug it further.

Cheers,
-P

[shack]

Yes they were removed from the PCB.

As far as calling it an ECU I guess it's semantics.

I agree, no microcontroller.. But I guess ECU stands for "electronic control unit", and I feel it fits that description... Even when it's not doing it very well!

This unit doesn't actually power anything, it just sends "requests" to the engine ECU.

The engine ECU then powers what it is asked to power via a relay, in this instance all under the drivers seat.

I put on my jewellers magnifying headband and checked all the connections, they look fine but I didn't reflow anything.

[prelude]

Ah, so it's only a level converter then.

I would hook it up and start measuring signals in/out. There should be a request line coming in, most likely ending up in the opamp and that should produce a signal out (on a pin) likely via a transistor and eventually ending up back on the connector.

The intermittent on/off is indeed a bit odd. If the line is switched to ground it might mean a short somewhere, if the line should be pulled up to 12v that makes it more likely a component failure of some sort.

I certainly do not have any documentation on this type of vehicle so if you have any, I can have a look :)

Cheers,
-P

[discorevy]

Have you tested the Trinary pressure switch James?

[shack]

Have you tested the Trinary pressure switch James?Not yet Craig,

Busy busy, but yes that would be a logical thing to rule out early on.


I've ordered some new bd139 transistors and some other bits as well, I think the total was about $12.

I possibly won't have much to report here for a bit with work and life etc.. also whilst it might be my imagination, the weather seems a bit cooler than it was.

It's been a killer summer and autumn, hence my fascination with staying cool...

But I'll see how I go, I'm sure the standard defender AC is capable of more than most are getting out of it.

[BradC]

I dunno how big the condenser is on a defender. On my old Volvo wagon I cracked the condenser on a Kangaroo. When I replaced it I went to the local auto-fridgie and crawled through the catalogue to find the largest (in all 3 dimensions) parallel flow condenser I could fit. That made a massive difference. It could ice the evap on a 45 degree day and even after a prolonged spell at the lights it was "cold enough".

I had the condenser fan set up to run any time the compressor was kicked in and the car was doing less than 70.

Originally I had it set up with the compressor and condenser fan on the same relay, but it turns out the condenser fan was windmilling fast enough that if the car was over 60, the compressor clutch stayed engaged. Took me _ages_ to figure out why it kept icing up on country runs.

Anyway, my rambling point was, if you don't already have a parallel flow condenser, put in the biggest one you can make fit.

[Captain_Rightfoot]

Did you measure them removed from the pcb?

It does look extremely simple. I would not even call it a ECU since there is no microcontroller on it :) It looks more like a logic level converter into anything 12v that the higher power electrics in the car can work with. Should be easy to test signals/voltages over those chunky in/out pins.

But first, I'd look for dry solder joints before you hook it up and measure voltages across the pins (the lm324n datasheets are all over). The BD139 can not power the AC clutch on it's own, it is rated at 12watts max and 1 amp current so those transistors are only used to power relays. (these use typically around 200mA max) so that's why they run without heat sinks.

I reckon two of the more beefy diodes are there to protect the transistors from flyback of the relais coils. Easy to test those too.

Back to captain rightfoot :) The VC fan would likely not run fast enough at idle to cool the condenser when it's really hot. That's why the thermo should kick in eventually. Well, if you've done some testing we'll debug it further.

Cheers,
-P
My apologies all. What I meant was I've never seen the electric fan on the front run at idle. The AC shop claimed they saw it run but I'd like to see it myself. Clearly I'll need to get it all hot and get someone to rev it while I watch. Maybe it's Schrödinger's fan.

It's looking like I'm going to do another double desert run in October. I'd like this to be working to the best of it's ability.

[shack]

My apologies all. What I meant was I've never seen the electric fan on the front run at idle. The AC shop claimed they saw it run but I'd like to see it myself. Clearly I'll need to get it all hot and get someone to rev it while I watch. Maybe it's Schrödinger's fan.

It's looking like I'm going to do another double desert run in October. I'd like this to be working to the best of it's ability.If you pull the viscous fan off and leave the car idling (keep an eye on the engine temp with your diagnostic gear) with the AC on, pressure should rise enough to cycle the condenser fan. If you can get hold of a nano, I can turn the condenser fan on at much lower engine temp and that will definitely help at low speed travel across the Simpson.

[shack]

Anyway, my rambling point was, if you don't already have a parallel flow condenser, put in the biggest one you can make fit.

I believe the early TD5 condenser was a smaller serpentine unit with no electric fan.

Later ones had a parallel flow with electric fan, the same as the puma defenders.

They are INSANELY expensive for a new genuine unit.

We have an early TD5 defender with the old style condenser and no fan, we are currently rebuilding the whole vehicle, I'll have more idea on how well it works once that's going.

[shack]

This is the early TD5 Defender setup.https://uploads.tapatalk-cdn.com/20250516/2a907ef6f6ec5c3ff4135b06f97c8d6a.jpg

[BradC]

This is the early TD5 Defender setup.

That looks like a conventional parallel flow. Oddly enough I can't see a defined subcooler there. Having said that, the inlet and outlet are on the same side, so there must be a division in the end tanks on the right hand side. That'll force the top of the condenser to work as a condenser as the gas flows right to left, then the liquid will fall to the bottom where it travels left to right to reach the outlet.

Anyway, if that's an early TD5 then it's not a serpentine. A serpentine is generally a single tube that snakes back and forward in a "zig zag" across the condenser. Worked perfectly well for R12, but r134a is so bad at rejecting heat they had to come up with something better.

In a car, anything you can do to reduce the condensation temperature is a bonus. Hiding it behind the intercooler is not going to help.

[prelude]

Schrodingers fan :) be careful you don't catch a cat in there mate!

Anyway, Shacks idea is excellent. Start with a cold engine, it will take a while to heat up, but the AC condenser should build up pressure quite fast. Without the airflow from the VC fan the thermo should kick in quite quickly with the AC blasting at full. See if you can measure the condenser temp (preferably on the inlet tube) whilst you are at it.

Funny how the old defenders did not have an electric fan. Old mercedes sprinter vans had the same thing, in traffic the pressure would simply go up to insane levels and the compressor would switch off.

-P

[shack]

That looks like a conventional parallel flow.

In a car, anything you can do to reduce the condensation temperature is a bonus. Hiding it behind the intercooler is not going to help.

It could be Brad, I haven't even looked at the picture I took! Just took it as I was walking past and kept going, I was however informed that the first series of TD5 had a serpentine.. So I've got into trouble "assuming"....

Early TD5 defenders have the intercooler in front of the condenser, late have it the other way around, possibly to incorporate the fan.

The old 300tdi had the intercooler off to the side.

I'm actually wondering now if the condenser in the latter ones is a little smaller.

I have an aftermarket one in mine which is a fair size, it couldn't fit a much bigger unit, I also have a genuine original that I'll check out later.

[Captain_Rightfoot]

And here is a serpentine flow condensor off a 2005 Defender

193299

[Captain_Rightfoot]

ok just spent some time looking at Schoedingers fan. I did get to see it run, but I was unable to determine what the trigger for it to run was. Sometimes it would sit there running indefinitely and not run, while the condenser got quite hot. Sometimes you'd start it up and it would run immediately.

I played around swapping relays and that didn't seem to make any difference.

[shack]

And here is a serpentine flow condensor off a 2005 Defender

193299I've been hunting around for a couple of spare condensers I have, finally found them.

Apologies, I've made a couple of blunders on this thread... Par for the course at the moment.

The early defenders OFTEN have a parallel condenser and no fan.

The late ones with factory air had a serpentine condenser and cooling fan.

My work vehicle is a late one and has a parallel flow (not standard)and fan, so literally anything could be installed now.

[shack]

ok just spent some time looking at Schoedingers fan. I did get to see it run, but I was unable to determine what the trigger for it to run was. Sometimes it would sit there running indefinitely and not run, while the condenser got quite hot. Sometimes you'd start it up and it would run immediately.

I played around swapping relays and that didn't seem to make any difference.Regarding what triggers the fan to run, I think I explained that earlier in this thread.

[prelude]

ok just spent some time looking at Schoedingers fan. I did get to see it run, but I was unable to determine what the trigger for it to run was. Sometimes it would sit there running indefinitely and not run, while the condenser got quite hot. Sometimes you'd start it up and it would run immediately.

I played around swapping relays and that didn't seem to make any difference.

Assuming the engine was cold (or at least not hot at that time) the condenser fan should only be operated by the AC. According to shack's observations 225 psi turns the fan on which should equate to a temperature of 55c. That is quite hot indeed :) Try and measure the temperature when observing the fan. If the fan does not switch on within specs I guess something is wrong with the system. Could be anything from the trinary switch to the small logic board that shack has troubles with.

In any case, also try and jump the relais for the fan, it should then always run regardless of ECU input, if your AC is cool then, at least you got a work around for your desert trip :)

Cheers,
-P

[shack]

While I'm waiting for other parts to arrive I've done a bit more on the system, today the switches. This is the globe for the backlight on them, would anyone like to have a good at what it is? 12v.

I'll order some new ones when I work out what they are.https://uploads.tapatalk-cdn.com/20250525/7264508f8ca70d7614269155286f6ba2.jpg


Edit: I think they are called a "grain of wheat bulb". Or rice etc etc

[BradC]

Yeah, grain of wheat.

12V Grain Of Wheat Globe 6x3.2mm - Altronics (https://www.altronics.com.au/p/s4063-globe-wheat-12v-60mah/)

[RANDLOVER]

Not to be confused with cob which is not corn cob but Chip On Board LED.[biggrin]

[Captain_Rightfoot]

Regarding what triggers the fan to run, I think I explained that earlier in this thread.
Sorry! what I meant was I have no visibility of the pressure switch. No way of testing.

[shack]

Sorry! what I meant was I have no visibility of the pressure switch. No way of testing.How do you want to test it? With a multimeter?

[Captain_Rightfoot]

How do you want to test it? With a multimeter?
Where is it located? :o There is a harness going to the compressor but I assumed that was the on off switch?

[shack]

It's basically screwed into the evaporator above where the right foot of a passenger would sit.

The fan is triggered by 3 things.

1. Engine temperature (coolant) while engine is running.
2. Engine temperature when engine off.
3. AC system pressure at the trinary switch.

Where is it located? :o There is a harness going to the compressor but I assumed that was the on off switch?

[Captain_Rightfoot]

Ok so I'm back from the desert again. It was mostly pretty nice temp wise, but we did have a couple of hot days. The AC might be working as good as ever but it fundamentally lacks cooling capacity when the days heat up.

The day I was doing some testing - high speed driving so should eliminate the issues of airflow over the condenser and engine speed for the compressor.

It was 38-40 degrees out, and the vent temp on medium fan was between 11 and 12. If you turned the fan up to high you got more air but the temps went up. Thermometer sitting on the centre console box was 33-34. (cry) So it is cooler than outside but not by a whole lot. The whole car gets heat soak.

I feel as though it's probably working as well as it ever has but it's just not even close to enough. IMHO I need some uprated parts here, but don't know who to talk to in Brisbane. Mr Cool did the work before I left, and while they probably got it working as well as they could within the parameters of the exisiting system, any actual improvements is beyond the scope of what they do.

Any ideas?

[Captain_Rightfoot]

That same day the engine was running in the 98-103 range. The viscous fan was only operating some of the time. I'm wondering if that is getting a bit average in its old age. (I can't recall it ever being replaced). While that's possibly a separate issue, could there be some crossover?

[shack]

The vent temperature output on my defender will go below zero on a 38° day and freeze the evaporator if I don't cycle it

[Captain_Rightfoot]

The vent temperature output on my defender will go below zero on a 38° day and freeze the evaporator if I don't cycle it
Cripes.. so WTF is wrong with mine!

[shack]

Cripes.. so WTF is wrong with mine!Can the Nanocom 1 upload tunes to the ECU?

[Captain_Rightfoot]

Can the Nanocom 1 upload tunes to the ECU?
Tunes.. not sure what you mean.

FYI when it was really hot I did look ant the little fan on the front was running.

[shack]

Tunes.. not sure what you mean.

FYI when it was really hot I did look ant the little fan on the front was running.A new engine tune, A Nanocom map.

[TonyC]

Cripes.. so WTF is wrong with mine!

Others on here understand AC better than me, but.

Is it gassed properly? Given it had a new compressor in May I assume so.

Is the compressor running all the time or cycling, if cycling is it the thermostat in the evaporator, or the pressure switch in the dryer, that's switching off the compressor?

Tony

[Captain_Rightfoot]

Others on here understand AC better than me, but.

Is it gassed properly? Given it had a new compressor in May I assume so.

Is the compressor running all the time or cycling, if cycling is it the thermostat in the evaporator, or the pressure switch in the dryer, that's switching off the compressor?

Tony
I assumed it was running full time (because the temp was fairly stable) but I will check that on the weekend.

[Captain_Rightfoot]

So update. Went for a drive yesterday (not a common occurrence for me). It was much much cooler outside. Mid-high twenties. Vent temps were typically 6-8 which works. Maybe that isn't so helpful.. if the weather is cool my ac works fine. :(

So while on the trip we were driving back from the desert. I was seeing coolant temps in the mid 100 range, which is higher than I've seen before. It was hot (39 ambient) but still that's pretty hot. I'm thinking first port of call might be to replace the clutch fan. Even if it doesn't help the AC I think that might help engine temps. I spun the fan just then, and when cool there is a lot of resistance. Feels the same hot or cold.

The other thing that might be next on the list. The condenser is showing signs of sitting on the front of a car for 20 years. Corrosion and general deterioration.

Thanks to chat GPT I found this mob which do a parallel flow drop in replacement.

LR025985 - High Performance Air Con Condenser for Land Rover Defender TD5 and Puma 2.4 and 2.2 Vehicles - Air Conditioning Condenser and Fan - by Coolair Logan (https://www.lrparts.net/lr025985-high-performance-air-con-condenser-for-land-rover-defender-td5-and-puma-2-4-and-2-2-vehicles-air-conditioning-condenser-and-fan-by-coolair-logan.html)

[TonyC]

So update. Went for a drive yesterday (not a common occurrence for me). It was much much cooler outside. Mid-high twenties. Vent temps were typically 6-8 which works. Maybe that isn't so helpful.. if the weather is cool my ac works fine. :(

So while on the trip we were driving back from the desert. I was seeing coolant temps in the mid 100 range, which is higher than I've seen before. It was hot (39 ambient) but still that's pretty hot. I'm thinking first port of call might be to replace the clutch fan. Even if it doesn't help the AC I think that might help engine temps. I spun the fan just then, and when cool there is a lot of resistance. Feels the same hot or cold.

The other thing that might be next on the list. The condenser is showing signs of sitting on the front of a car for 20 years. Corrosion and general deterioration.

Thanks to chat GPT I found this mob which do a parallel flow drop in replacement.

LR025985 - High Performance Air Con Condenser for Land Rover Defender TD5 and Puma 2.4 and 2.2 Vehicles - Air Conditioning Condenser and Fan - by Coolair Logan (https://www.lrparts.net/lr025985-high-performance-air-con-condenser-for-land-rover-defender-td5-and-puma-2-4-and-2-2-vehicles-air-conditioning-condenser-and-fan-by-coolair-logan.html)

By mid 100s I assume you mean 105, not 150.
From what I've read on here, the TD5 AC is controlled by the ECU, but I may be confusing it with a Disco TD5, so if your coolant temps are up, the car maybe switching the AC off.
Shack would know

Do you have a Nanocom? Can it tell you if the AC compressor is on or off?
If it's running all the time I'd be suspecting it's under gassed.

I'm no AC expert so If anyone thinks I'm off track please chime in.

Tony

[shack]

From what I've read on here, the TD5 AC is controlled by the ECU, but I may be confusing it with a Disco TD5, so if your coolant temps are up, the car maybe switching the AC off.
Shack would know


Tony

The engine ECU on both the D2 and Defender will both turn off the A/C when the engine temp reaches 116° with only 1° hysteresis to cycle back on.

On the D2 the ATC controls A/C functions, but requests get passed to the engine ECU which then relays the final requests to the individual components.

On the Defender, operation is very similar only the ATC is missing and a small "unit- Air conditioning" is used instead.

Let's do some mental diag...

The compressor on the Defender will cycle for 3 reasons.

1. requested evaporator temperature has been reached (included in this is if the evaporator is in danger of freezing).

2. system pressure has risen too far.

3. Engine temperature is too high.

If system pressure is getting too high the condenser fan will switch on before the compressor will be disabled.

If the compressor is turning off BEFORE the condenser fan turns on, then it is being cycled by the thermistor and A/C unit, due to the evaporator temp having been reached.

If the compressor is cycling without the condenser fan running before the air from the vents gets very cold

( and I'm sorry here as there is no definitive temperatures given in any official document that I've found, and I haven't been able to test a good one....)

then it's LIKELY that either the thermistor or A/C unit has failed.

It's unlikely that the A/C will cycle off due to low pressure once it has started.

This only applies to the TD5 Defender.

Hope that helps!

[TonyC]

The engine ECU on both the D2 and Defender will both turn off the A/C when the engine temp reaches 116° with only 1° hysteresis to cycle back on.

On the D2 the ATC controls A/C functions, but requests get passed to the engine ECU which then relays the final requests to the individual components.

On the Defender, operation is very similar only the ATC is missing and a small "unit- Air conditioning" is used instead.

Let's do some mental diag...

The compressor on the Defender will cycle for 3 reasons.

1. requested evaporator temperature has been reached (included in this is if the evaporator is in danger of freezing).

2. system pressure has risen too far.

3. Engine temperature is too high.

If system pressure is getting too high the condenser fan will switch on before the compressor will be disabled.

If the compressor is turning off BEFORE the condenser fan turns on, then it is being cycled by the thermistor and A/C unit, due to the evaporator temp having been reached.

If the compressor is cycling without the condenser fan running before the air from the vents gets very cold

( and I'm sorry here as there is no definitive temperatures given in any official document that I've found, and I haven't been able to test a good one....)

then it's LIKELY that either the thermistor or A/C unit has failed.

It's unlikely that the A/C will cycle off due to low pressure once it has started.

This only applies to the TD5 Defender.

Hope that helps!

What makes the system pressure to go high? That the condenser can't shed enough heat?

If the system is not cycling but not getting really cold, is low gas the likely culprit?

Tony

[shack]

If the condenser fan isn't running, then possibly yes.

I can't remember what bits you have replaced, but a faulty TX valve or compressor can also be the issue.

I should point out that the temps I quoted are when driving at 70+kmh and I have over ridden the thermistor but not the pressure switch. I have a faulty thermostat or A/C unit.

[Captain_Rightfoot]

Ok so update from testing.

The TD5SPY doesn't have the functionality to report if the compressor is on. However it does have a test button where you can test various systems while the car is off. The test button for the fan worked, and for the compressor also worked. Clearly the ECU is actively controlling these.

So I went for a drive around town .. not long but it's hotter today. 30 ish. The engine temp didn't get above 89. Vent temps on the ac were 6-8 when I left home and the car was cool. After parking in the sun for a bit they were around 10-11.

So I sat the car in the driveway and left it idling to try and get the temp up. It didn't really get above about 89. The compressor was running the whole time AND the condenser fan. Vent temps were 14!!!

I shut the engine off and ran around and tried to spin the clutch fan. It was spinning very freely. Even more freely than when cold. Like a turn or maybe more.

Work completed so far. new compressor, new TX valve, obviously a full regas. Evaporator cleaned. Condenser is as clean as a 20 year old condenser gets.

PS I don't know what's wrong with this thing - but it feels as though it needs significantly more capacity for when it's hot.

[BradC]

So I sat the car in the driveway and left it idling to try and get the temp up. It didn't really get above about 89. The compressor was running the whole time AND the condenser fan. Vent temps were 14!!!

Get it like that again, then give the condenser a squirt with the hose and see what happens.

Idling is not a good test. The compressor isn't moving much gas and the fan isn't pulling a lot of air through the condenser. You really need to be sitting around 1200-1500 rpm for a representative test. Lots of systems suck at idle and not moving.

[Captain_Rightfoot]

Get it like that again, then give the condenser a squirt with the hose and see what happens.

Idling is not a good test. The compressor isn't moving much gas and the fan isn't pulling a lot of air through the condenser. You really need to be sitting around 1200-1500 rpm for a representative test. Lots of systems suck at idle and not moving.
I have done that in the past and it made a measurable difference (spraying the condenser)

[Captain_Rightfoot]

ok breakthrough. Removed the clutch fan despite it "feeling good".

Hit the bimetallic spring with heat and it doesn't move the shaft. Win. Explains the running hot and maybe the AC. Tomorrow job!

[discorevy]

ok breakthrough. Removed the clutch fan despite it "feeling good".

Hit the bimetallic spring with heat and it doesn't move the shaft. Win. Explains the running hot and maybe the AC. Tomorrow job!

Common problem at 20 odd years old, replace with the OEM unit ( Borg Warner ) Part number PGG500340

[shack]

Common problem at 20 odd years old, replace with the OEM unit ( Borg Warner ) Part number PGG500340Unfortunately a lot of sellers are calling "bearmach" and "allmakes" OEM, which is slightly naughty to say the least, and most still charging just under $500au.

Caveat emptor I guess.

[discorevy]

Unfortunately a lot of sellers are calling "bearmach" and "allmakes" OEM, which is slightly naughty to say the least, and most still charging just under $500au.

Caveat emptor I guess.

Yep, you'd want to ask if Borg Warner is stamped on the unit.

Allmakes is owned by Britpart, but they are resellers rather than manufacturers.

These were B.W. units, last time I got one:

Viscous & Fan Td5 2.4 Puma (Britpart OEM) PGG000180 PGG500340 (https://www.island-4x4.co.uk/viscous-fan-td5-2-4-puma-britpat-oem-pgg000180-pgg500340.html).

or Locally:

Fan & Viscous Coupling TD5 PGG500340 (https://www.british4wd.com.au/fan-viscous-coupling-td5-pgg500340)

[Captain_Rightfoot]

So it's hard to test extremes of heat when it's just not that hot. I took the car for a drive last week with the new thermo fan. It was probably high 20's. I think it's definitely running cooler. You can hear the thermo fan... which I haven't heard for a while. So I think at least it's addressed the engine cooling.

The AC was running 5-7 which is is pretty reasonable. Cabin temps were pleasant. I'm not game to call it yet though. Need a stinker.. I see we've got 37 forecast later this week (WTF Brisbane). I think i'll go for a drive at lunch.

So any thoughts on this? It looks like it would help. At the very least the old one is looking a bit like a 20 year old condenser. These are sold as drop in "performance upgrades". They switch from serpentine to parallel flow.

https://cdn11.bigcommerce.com/s-cc6n4ysez6/images/stencil/805x805/products/267872/63106/CAL_Condenser_comparison__23346.1723643299.jpg

LR025985 - High Performance Air Con Condenser for Land Rover Defender TD5 and Puma 2.4 and 2.2 Vehicles - Air Conditioning Condenser and Fan - by Coolair Logan (https://www.lrparts.net/lr025985-high-performance-air-con-condenser-for-land-rover-defender-td5-and-puma-2-4-and-2-2-vehicles-air-conditioning-condenser-and-fan-by-coolair-logan.html)

[shack]

There are much cheaper upgraded condensers available for the late TD5 Defenders, I can't find any in Australia at the moment though.

I have one in my work bus, but it is most definitely NOT bolt in, I can't remember exactly what I had to change though.

It seems to work ok.

[Captain_Rightfoot]

There are much cheaper upgraded condensers available for the late TD5 Defenders, I can't find any in Australia at the moment though.

I have one in my work bus, but it is most definitely NOT bolt in, I can't remember exactly what I had to change though.

It seems to work ok.

Interesting. Would you say the upgraded condenser helped the AC?

They are saying the landed price would be 1700 AUDs. If it's "drop in" extra purchase cost could mitigate paying people to modify aftermarket solutions.

Am I at the stage of being prepared to just throw money at this problem? Not quite. But nearly.

[shack]

I really couldn't say if it made any difference over the stock condenser as the AC want working when I got it, the first time it worked was with the new one.

I think the new one is parallel and it is a bigger unit than the stock one, it covers the whole radiator from memory.

I can tell you with the viscous fan removed and just the electric one on, when pressures in the system gets high and the fan cuts in, the pressure drops rapidly over a number of seconds and the fan cycles back off.

[Captain_Rightfoot]

I really couldn't say if it made any difference over the stock condenser as the AC want working when I got it, the first time it worked was with the new one.

I think the new one is parallel and it is a bigger unit than the stock one, it covers the whole radiator from memory.

I can tell you with the viscous fan removed and just the electric one on, when pressures in the system gets high and the fan cuts in, the pressure drops rapidly over a number of seconds and the fan cycles back off.
Thanks. In the testing I've done - when the fan is on it seems to just stay on. I'll have an extra close look on Thursday when I take it out for a run on our hot day. It's won't be desert hot, but should give me some idea. Birdsville forecast is 45 today, 44 tomorrow!

[Captain_Rightfoot]

I'm struggling to get testing conditions to verify the new clutchfan. I can say though that it's more active and can be audibly heard. I haven't really seen any temps above 90 but it hasn't been stupid hot.

I also played spray the condenser again yesterday. It changed the temps significantly.

[RANDLOVER]

It's going to be stupid hot in Brisbane today.

[Captain_Rightfoot]

It's going to be stupid hot in Brisbane today.
Unfortunately I have a funeral. :( Also the car is in to have the fuel tank dropped and hopefully the leak fixed.

I'm sure there is going to be an opportunity in our near future.

[Captain_Rightfoot]

It's going to be stupid hot in Brisbane today.
I just want to say, I cannot recall Brisbane ever having such a textbook copy of what it's like in Birdsville in October. Dry and hot. It would have been ideal for testing the AC and car cooling. :(

[Tombie]

It's going to be stupid hot in Brisbane today.

Still didnt beat 1957s record [bigsmile]

And when did 38.7c become stupid hot? RH was down below 50% - would have felt like a nice day [biggrin]

[Captain_Rightfoot]

So I have the car back again. Drove home and would like to confirm I'm convinced that the clutch fan is working more often.. as soon as the car goes over 90 it starts.. so then it's back below 90. I don't expect I'll see the 105 I saw on the last trip.

The AC meanwhile.. was working ok (6-7 vent temps moving, 8-10 ish stationary) today but wasn't that hot. The mechanic suspects it could be the chinese compressor I just had fitted. [bighmmm]

Next wednesday I'm taking it to another AC mechanic purely for an evaluation.

[Captain_Rightfoot]

So the update is the car went to another AC person yesterday. "European specialist". Good reviews.

They looked at the car. He said the system is operating perfectly. All the pressures etc are perfect. It's just lacks cooling capacity.

On the drive home it was sitting at about 7.5 and then every lights it would start creeping up pretty quickly.. typically it would get to 10 or more at a set of lights. If you let it sit idling it hits 13. The fan was running when I looked when idling at 13 degrees.

He suggested the new condenser is probably as good a place to start. It's a known weak point of the system. Massive cost, but I'm not sure what else can be done.

[Captain_Rightfoot]

I just want to record this for my future reference.

Trip to pick up camper. Highway and light urban. Middle fan.

Morning. 7.5 deg to 9 Deg.

Afternoon (hot 31, 32). 9.5-11 Deg. Slower speeds- higher temp.

I tried high fan but then the temps went up to 13.:(

[Captain_Rightfoot]

I bit the bullet. Twin fan parallel flow condenser on the way from the UK. The actually claim it's got enough capacity to run their second air conditioning head that they make that replaces the centre console box. Apparently the factory compressor and this condenser can run both the front AC and this one. Interesting Idea though. 3700 pounds if you're asking for the Box.

I suspect that IS the answer but we will see with just the condenser.

Centre Console Air Conditioning Kit For Land Rover Defender | STAUNCH (https://staunchauto.com/product/centre-console-aircon/)

[Captain_Rightfoot]

The weather forecast in Brisbane is 34 tomorrow, and then a couple of 36's before dropping to 30 and then heading back up. Another crazy hot spring week.

I do think trying to get the AC working is super important if you want to run these cars in this heat.

[discorevy]

The weather forecast in Brisbane is 34 tomorrow, and then a couple of 36's before dropping to 30 and then heading back up. Another crazy hot spring week.

I do think trying to get the AC working is super important if you want to run these cars in this heat.

I don't live in Brisbane ( though I was there in Oct briefly to help a mate sail his boat to Sydney, it's now in Albany ) but I thought the seasons were the same as the rest of Australia, which has been Summer in the southern half since the start of December.

Is mid 30's "crazy hot" for Brisbane late December?

Not meaning to have a crack, but also, I don't think AC is super important for the car, maybe the driver

[Captain_Rightfoot]

I don't live in Brisbane ( though I was there in Oct briefly to help a mate sail his boat to Sydney, it's now in Albany ) but I thought the seasons were the same as the rest of Australia, which has been Summer in the southern half since the start of December.

Is mid 30's "crazy hot" for Brisbane late December?

Not meaning to have a crack, but also, I don't think AC is super important for the car, maybe the driver


but I thought the seasons were the same as the rest of Australia, which has been Summer in the southern half since the start of December.

Sorry senior moment there. [bigsmile]

It's not unusal for Brisbane to have a hot day or a hot day or two here and there. But now we seem to have hot week after hot week. In my lifetime, serious floods affecting Brisbane were 1974, 2011, 2022, 2025. Anyway that's probably another thread.

The AC has been marginal in this car since it was new. I'm sure the system has degraded at least somewhat since new which is probably not helping things.

Yes, you are right AC is more for the driver than the car. I help with a desert race in late Sept/Oct each year. It's not uncommon for there to be a week (or two) of 40 degre days. When it's 40 outside and 35 inside the car that does wear on me for sure. My friends in their toyots sitting inside at 22 are definitely less affected by the heat. :o This year we found we were probably better to have the ac on and the windows down because the ac blowing air at you that's mid teens is not overly helpful.

[Captain_Rightfoot]

Looks nicely made. We will see if it helps. [thumbsupbig]

https://lh3.googleusercontent.com/pw/AP1GczNy3Cy-TzztCL2y4HFFU8bS336_GRiwP-OWnchFP9-rpIIDXPMyVtHfUIzNamAkkUUTmLcxORPyJ2nywUZaGID0CpvAs JjwlBARAHJOm824sVU_hk6Pu-bZpRmpOMz59etXp7vRMKkJdY-J0DTD3A9p=w2814-h1582-s-no?authuser=0



https://lh3.googleusercontent.com/pw/AP1GczOcxd87J-4iuk5HPNbc4IWIHFlbvJEs7_Zf3q55wteJt6iiagAz57JhH0GX 3dn1HdeXCm7b9Tx5P8qqMeCUVBfiVjThBCghXnAu_SWWwsg7hT B0rvSuZqy7wTBF4KhJtMezvGwzZQ5WLsBm90psfWgz=w2814-h1582-s-no?authuser=0

[Captain_Rightfoot]

Putting this in for later for me.

Drove back from the coast. It was hot. Forecast 38 but it wasn't quite that bad. Humid as well. On the trip back from the coast mid morning the AC was blowing 8 to start with and 9 as it warmed up on medium fan speed. When I got to brisvegas and in the traffic was in the teens. The temperature on the centre console box was 30.

It's new condenser week Thursday and Friday. I'm trying to hard to manage my expectations. [bigwhistle]

I don't expect it's going to make the AC a Toyota. It will always be a small AC in a big white box - but if I can get it to consistently blow more 4 or 5 and hold that temp on high fan on a hot day I think that will be good as i can hope for.

[shack]

A balmy 45 here today.

AC is working pretty well, this is the vent air temp with fan on 2 and at cruising speed.
https://uploads.tapatalk-cdn.com/20260127/f3f9dd246c77a10b2bb660e0d69bb541.jpg

[Captain_Rightfoot]

A balmy 45 here today.

AC is working pretty well, this is the vent air temp with fan on 2 and at cruising speed.195625

I wish! [bawl]

Do you think it's adequate for the car when it's working like that?

How on earth has yours got so much more cooling capacity? :(

[shack]

I don't know, but it's probably a combination of the following:


1. It's using hychill not R134a. It's more efficient.

2. I've got a parallel flow condenser.

3. I've changed engine mapping to run the electric fan sooner.

4. The little ECU that controls all AC functions has failed on the the thermostat control side (I think a lot of them have) so I've bypassed the thermostat whilst leaving the condenser fan control and trinary switch operation in place.

5. I've bumped idle speed when the AC is on to provide better cooling when stationary.

6. I've done considerable heat insulation on the vehicle to reduce heat ingression, as the evaporator will only Cool air by a certain amount below the ambient temp in the car.

I've still got exhaust heat shields to fit and several other mods when I can get too it.

Significant heat comes into the cab from the exhaust as there is NO shielding at all from factory.

As to whether it's acceptable... Mine is a twin cab so less space to cool, I went for a 15 minute drive today, 45°outside with the car parked in it for hours before hand, internal temp was 50° but had dropped to 28° from memory when I stopped.

It's not bad in the front but the back might make you a bit testy.

[Captain_Rightfoot]

Bravo!

I will ask for hychill when they do the work.

The rest of those items sound like a priject. I 100% agree with the heatsoak. The temps coming up from the floor are insane.

[shack]

It's Hychill -30 in mine, there's a few different ones but that's the correct one for this job.

[Captain_Rightfoot]

I just want to record this for my future reference.

Trip to pick up camper. Highway and light urban. Middle fan.

Morning. 7.5 deg to 9 Deg.

Afternoon (hot 31, 32). 9.5-11 Deg. Slower speeds- higher temp.

I tried high fan but then the temps went up to 13.:(

Ok so finally I have an update. Car came back on Friday after two months of languising at the auto electrician/AC place.

So I haven't really done other anything other than short drives around town. It was warm yesterday (about 30). The AC typically seems to cycle on and off and run at about 5.5-6.5 when running. Cruicially this doesn't seem to change even if you run the fan speed on high which is very different. In the past if you ran the fan high you got more air but it was massively warmer.

At idle it does drift up to 8 or so after a couple of lights. Again a big improvement. Unlike the system in the past that took 10 or 15 minutes to get the temps down it now has the temp onto 5 within a minute or two.

The temps are now mostly below 30. I'm taking it away at easter hopefully. Will report.

[DoubleChevron]

Ok so finally I have an update. Car came back on Friday after two months of languising at the auto electrician/AC place.

So I haven't really done other anything other than short drives around town. It was warm yesterday (about 30). The AC typically seems to cycle on and off and run at about 5.5-6.5 when running. Cruicially this doesn't seem to change even if you run the fan speed on high which is very different. In the past if you ran the fan high you got more air but it was massively warmer.

At idle it does drift up to 8 or so after a couple of lights. Again a big improvement. Unlike the system in the past that took 10 or 15 minutes to get the temps down it now has the temp onto 5 within a minute or two.

The temps are now mostly below 30. I'm taking it away at easter hopefully. Will report.

Have you hot wires the condenser fans yet to see if it helps with the cooling capacity?

[Captain_Rightfoot]

Have you hot wires the condenser fans yet to see if it helps with the cooling capacity?
So the new condenser has dual fans. I've only seen them running once but they looked like they were going hard. I noted there was some hot air swirling back out of the condenser like it had nowhere to go behind. Maybe I need to investigate this. The td5 intercooler is next in line. It looked ok.