Thread: TD5 Airconditioner efficiency.

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.

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

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

Originally Posted by Captain_Rightfoot

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?

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:

1. pressure too low, this happens when the system has a leak or whatever and there is not enough gas. It would never work
2. 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)
3. 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

Originally Posted by shack

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.

Originally Posted by 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:

1. pressure too low, this happens when the system has a leak or whatever and there is not enough gas. It would never work
2. 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)
3. 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.

Originally Posted by prelude

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.

Originally Posted by Captain_Rightfoot

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.