Air con wiring advice needed?

[fender22]

Recently got a 2nd hand air con from the wreckers fitted in my 200tdi. Was the original under dash one from another 93 defender.

Freezing cold and generally works well but seems to be too big a differential between cool on / cool off. Can't seem to get a handle on it either?

Usually comes on when I start the engine, then after a few minutes will go off, then may or may not come on again in the next few minutes. I can feel the load on the engine as soon as it kicks in again, and I hear the thermostat clicking in and out. The fan runs constantly of course when on 1,2 or 3.

Just trying to get an understanding of how it works? Maybe I can improve things. I thought at one stage having the window open a bit was making the compressor go off

For eg:
Are the system electrics basically as simple as the thermostat just operating the compressor clutch on and off, or is it also controlled by pressure or something else?

The rotary thermostat control. Is this a potentiometer or something? Should it over ride the thermostat / be full on all the time when turned to full?

I'm thinking of taking it to an air con guy and telling him to wire it so that as long as I have the fan on 1,2 or 3...the air con be on constantly. If I don't want air con I'll turn the fan off and use the vents or wind the windows down

[p38arover]

The wiring diagram should be in the files section. I know I've uploaded it on the forum in the past. A search should find it.

[fender22]

How am I supposed to understand that? I'm an electrician :-)

[Don 130]

31886
This hasn't saved very well . I'll try to reload it later. Don

[fender22]

Just found it thanks. Easy enough but I'm trying to find out basically the principle of how it works? Understand the thermostat and what it does of course. I see a pressure switch in there? How does that work, what does it do/

Someone suggested mine may be cutting out on high pressure with the modern gas.

[fender22]

Other thing I meant to ask. Does it bring in fresh air or recirculate the air in the cabin? Seems to get awful warm awful quick once the compressor stops

[Blknight.aus]

thread up (http://www.aulro.com/afvb/technical-chatter/119268-ac-101-a.html#post1391243) (Im too lazy to cross load all the f111 pics atm so I'll do AC instead)

[alhedward]

You still having issues with Aircon?
Did you get the electronic wizbang from inside the battery compartment? This is the thermostat amp (so called). The rotary knob adjusts the temperature by comparing the actual cool air temp with a reference inside the amp. If you do not have this item, then the temp will either be freezing or off.
It is a necessary item due to the evaporator being subject to icing up quite readily and then there is no airflow through the evaporator and the compressor will not cut out. I have a hand drawn cct diagram that I can let yopu have if you are still in need.

[alhedward]

recirc only

[fender22]

Would appreciate it if you have it mate. Don't think it's in the battery compartment, don't know where they put it but I assume down near the fuses. This isn't an original fitting but one from the same model bought from a wreckers.
Pretty much how it is though, either freezing your face off or off. Do they draw air from outside or just recirculate? I can hear a click inside the cabin though when thermo cuts in and out. Is the thermo switch integral to the thermostat amp? ie would this click be coming from where the amp is?

[brett43au]

Hi Im alos having problems with the air con in a 97 defender . It looks simple enough with all the wiring going back to a set of realys and a black box in the battery well . I cant get power at the compressor clutch . Solenoids seem to click as does the large black box in the battery box fuses all look OK . What did you serach on the find the wiring diagram as I have tried a few serches and cant find it .
Rgds Brett

[fender22]

Does anyone know an air con guy around the bayside / Carindale / Wishart / Cannon Hill area of Brisbane. Someone knows LR preferably

[Blknight.aus]

Hi Im alos having problems with the air con in a 97 defender . It looks simple enough with all the wiring going back to a set of realys and a black box in the battery well . I cant get power at the compressor clutch . Solenoids seem to click as does the large black box in the battery box fuses all look OK . What did you serach on the find the wiring diagram as I have tried a few serches and cant find it .
Rgds Brett

that will usually be a burnt relay seat or contact if your lucky and the compressor clutch wires/plug if your not.

Fender 22, I'm 50 Km away if that counts as close.

[alhedward]

Here is the cct diag.

If unclear, here is a rough legend
Resistor: top left
Blower switch: below resistor
Blower motor: to right of resistor
Thermo Switch below Blower motor
Temp Probe: to right of Thermo Switch
Compressor clutch: half way down on right
Pressure switch: to left of clutch
Relay: to left of Thermo-Amp
Double rectangles are the inline connectors
Thermo-Amp: rectangle with 8 leads

Top dotted line is all inside internal aircon unit

Bottom dotted line should be in battery compartment.

Operation:

12v is provided via relay from ignition switched source.
Thermo-amp is powered once blower switch set at 1 to 3.
Temp Probe sends signal to thermo amp which compares with internal reference and Thermo rotary switch position.
12v supplied to compressor clutch if probe temperature higher than thermo-amp result.
cooling via evaporator/compressor/condenser plumbing.
Once probe signal reaches desired value, Thermo-amp shuts of compressor.
The pressure switch can differ between installations as some have a high/low pressure switch.

If temp of refrigerant gas gets too high, pressure increases beyond threshold of pressure switch and cuts power to compressor. If refrigerant gas leaks, pressure is then to low and switch cuts supply to compressor.

If single switch, If pressure too high then compressor power is cut.

Suggested mods.

Fit trinary switch to receiver/drier and fit electric fan in front of condensor. run the fan through a relay switched by trinary switch high pressure wires and series up the low pressure wires to the compressor (this will ensure you don't run the compressor without refrigerant).

Remove and drill/tap blank hole in thermostat housing and fit normally closed temp cutout switch to over ride pressure switch. This will shut a/c off if engine temp climbs above threshold of temp switch. If you want to go a little further, drill/tap other blank hole and fit normally open temp switch and feed in parallel to relay that drives fan. This will allow you to have additional forced air through radiator, especially when off-road or in heavy stop start traffic.

Both these temp switches are standard in the disco 300tdi a/c system.

Hope this all helps

Tony
31916

[fender22]

Really appreciate your trouble mate. I have a 200TDI defender. Would the wiring diagram be the same?

[Don 130]

I found this copy in 'the good oil'
http://p38arover.com/rover/defender/AMC%20Air%20Con%20Defender.gif
Thanks to Ron AKA p38arover
Don

[isuzu110]

Does anyone know an air con guy around the bayside / Carindale / Wishart / Cannon Hill area of Brisbane. Someone knows LR preferably


Yes, see here for details at end of post http://www.aulro.com/afvb/90-110-130-defender-county/106675-tdi-defender-air-conditioning-fixed.html

[fender22]

K2 Air con is the guy I have looking at mine on Wednesday! How lucky is that.
I asked him if he knew LR and he just said yes. I thought to myself sure...

[alhedward]

You can use a manual thermostat with a capiliary tube to set the temp instead of the thermo amp. Any A/C service guy can fit this.

[fender22]

Had a guy look at it today however he said it was an electrical problem and will need an auto electrician. Sounds like a dodgy relay or bad earth or something. I could hear it clicking in and out, thinking that was the tstat but apparently the click is from the relay when it's intermittently getting power.

[fender22]

As a quick follow up, got in the car this morning and air con working perfectly, cycling on and off like a champion. I'm not expecting it to hold out but at least I know it's just a dodgy connection somewhere. He must have moved the harness around and it's come good.

[fender22]

Only lasted a day. Back to where I started again!

The air con guy tested it and said it's fine mechanically and it's an electrcial fault and he could only test the fridge side. He said there was intermittent power going to the compressor apparently, 3 spd fan runs fine...... And thats what it does. Fan runs correctly and constantly, but then compressor will cut out for 5 to 10 minutes, air gets warm and ventually comes back on again. From other posts I'd read I thought it must have been icing up or something but the fridge guy says it's not that either.
I am an Electrician but not the auto type which usually gets me into more trouble than it's worth on vehicles. Anyway, he must have fiddled around with something because it came good for a day, worked perfectly and now it's back to intermittently shutting on and off.

I was hoping the problem may have been as simple as a loose relay connection but it looks by the wiring diagram if the power relay was faulty the 3 speed fan wouldn't work either. So the likely culprit will either be the connection plug off the thermo amp, the thermo amp itself. What do you guys think? Rgds Craig

[Blknight.aus]

it'll be one of a few things

1 the evaporator freezing up cooling stops the refirigerant gets no heat from the air (ice is an insulator) so stays liquid in hte evaporator and the High pressure cut out is taking effect, the same thing happens if its been over gassed.

if you're ABSOLUTELY sure that its not the evaporator icing up then bypass all the electrics and feed the compressor directly from the battery with the engine running and see how long it blows cold air for

having a set of aircon gauges will make diagnosing easier but you need to manually measure the temp of your piping

it should be hot going into the condensor from the compressor
cooler but still warmish going from the condensor to the TX valve
Cold coming out of the TX to the evaporator and
cool going from the evaporator to the compressor.


you may find that the if the TX valve has had a smack during removal/install that its not working properly Or the system has contaminates in it and something is blocked.

[fender22]

Definitely appears to be electrical. Spoke to the fridgy this morning and he put guages etc on the lines, tested all that size. He reckons it came good when he started playing with the wiring near the fuses , relays. Ran perfectly for a day then **** itself again

[Blknight.aus]

in that case...

try the manual bypass trick on the compressor with a 12v 10w bulb wired up to the normal wiring.

IF the light goes out but the AC is still pumping out nominal cold air then its time to follow the wiring backwards from the clutch connection.

Dont forget that this can also be a symptom of the compressor clutch or the wiring on the way out and this will be revealed by the compressor stopping with the bypass wiring still in place but the light staying on.

[fender22]

By the way mate, If I do connect the compressor directly, and it still cuts out that means it is icing up eh? I wont do any damage without the high / lo pressure switch in circuit? The air con guy told me that it's very rare they play up.

[fender22]

So where do you connect the 1w bulb mate? Accross the compressor terminals?
Sorry mate, clearly I don't have a clue :-(

So if it ices up, the compressor wont be receiving power anyway eh? because the pressure switch will cut off power to compressor? So I'd have to wire the light before the pressure switch to see if it's losing the feed somewhere before the pressure switch. If that's the case I know it's wiring. Couple of dmba$$ questions...

Where is the pressure switch? next to the compressor?

Are there relays / fuses etc mounted in the underdash unit itself and if so can you get to them? The air con guy thought the air con relays / fuses where mounted with the other fuses under the dash in the fuse box

[Blknight.aus]

ok, find the compressor it will have a connector on it.

disconnect that compressor

wire a light from one (if its the 2 pin type) of the connectors to a light and then to earth. Turn on the ignition and the AC the light should light, if it doesnt try the other pin. If its a single pin wire a 10w light in place from it to earth.

this light tells you what the AC system is telling the compressor to do.

now go straight from the battery + to the compressor and you should get a nice healthy clunk as it engages.

start the engine and within about 30 seconds or so you should be getting cold air.

At high idle (call it 1K RPM) with the doors open and the fans on the lowest speed you should see the light go off, when it does ramp the fan speed up and back off the engine RPM's and you should see the light come back on this means that the system is correctly cycling the the compressor. so Excluding the TX valve sticking (which happens but is rare) its going to be an intermittant electrical fault.

IF the light stays on but the cold air stops then its an intermittant fault in the refrigeration system that is pretending to be an electrical fault OR the compressor clutch is dodgy OR the compressor is knackerd.

[fender22]

I understand (I'm an electrcian but don't have a clue about DC!)
So the compressor will be hotwired, which means if all good on the mechanical side should stay cool indefinitely.

The light is attached to the signal coming from the thermo amp which would normally power the compressor, cycling on and off. I can't do any damage running the compressor like this (over riding the pressure switch?)

Makes perfect sense and even if I don't fix it myself will be able to point an auto elec in the right direction

By the way, if I'm looking for an electrical fault, where are the relays etc normally mounted. On the wiring diagram say they're in the underdash unit. Are they in a place where u can get to them or do I need to drop the under dash unit down.

Looks like there's a main power wire running to the thermo unit off the fan switch. If there was a fault anwhere past there the fan would still run but compressor could be off. Basic likely places to look appear to be the plug / harness to the thermo amp, and the connections from there out to the pressure switch / compressor. Unless it's a crook thermo amp?

[Blknight.aus]

now you're on the money....

yes by running the compressor indefinately hardwired you can cause it damage IF you dont put enough heat to the evaporator the evaporator will freeze the TX valve will close up and the pressure will rise eventually one of 2 things will happen you will get liquid feed back to the compressor from the suction line when the tX valve is overpowered OR you will put too much pressure head on and blow something apart, both cases are bad.

Dont be worried about DC vs AC power the basics are the same but our power knows which way its going. Think single phase sans earth and your on the tracks you need to be on. Oh if you see triple digits before the decimal on a meter in DC worry.

My suggestion is to follow the wiring from the Fan switch one side will lead to the main power fuse (which we know is ok) one side the fan/fan resistor pack and the other should lead to the AMP. As per the diagrams provided in earlier posts.

IF that gives you no joy you need to follow the wiring from the temp control switch.

Yes dropping the unit is a PITA.

[fender22]

Really appreciate it mate, have a clear picture of what I need to do and how it operates now. Wish it wasn't xmas tomorrow I'd have time to play around with it.
I'd much rather spend the day with Beryll :-)

Thanks again mate and have a very safe and merry Xmas

[fender22]

Oh, one more thing mate. The more I think about it and may be wishful thinking but the air con guy reckons it was definitely coming on and off when he was pulling at the wiring at the fuse box. That would lead me to suspect the wiring off the three speed switch as its in that proximity.

To get at the switch is it just a matter of undoing the four screws at the top of the underdash unit and dropping it down a bit to get at it?

[Blknight.aus]

from memory the switch plate that its mounted in is only a pressin fit or secured by a handfull of screws.

undo those and it should pop out... Last one I did I fixed by pulling out one of the vents and probing at it from inside the ducting.

merry Xmast to you too mate, and if you cant get it sorted before mid JAN drop me a hoy when I get back and we'll ine out sorting it over some coldies.

[alhedward]

In a very rough sense, regard the negative side of the battery as the Neutral/Earth in AC and the Positive side of the battery as the Active in AC. The only difference is that DC is always traveling in one direction as opposed to AC which travels in both directions alternately. Any metal part of the car can be regarded as Earth, In most instances any Black wire can be regarded as Neutral and any Brown wire is a direct feed from the Positive side of the battery, Regard this as Active.

There is a standard for British cars wiring loom colours and I shall attach the PDF in this post.

This will allow you to get a feel for what does what in your wiring loom. It is not necessarily 100% as your vehicle may have had mods done to it by previous owners.

Any original wiring will be in a taped loom so that should make it a little easier to decipher.

32000

[Blknight.aus]

not quite, you regard DC negative as the earth From AC and you are going to come acropper..

assuming a "negative earth" vehicle configuration. (negative terminal connected to chassis/body)

assume that the negative is neutral and positive is active.

[fender22]

Hello. Spent a couple of hours fiddling with the air con today and nothing was as it should be on the wiring diagram I have. Wiring colors on the back of the three speed switch were all different. Any way, persevered and fiddle around and I think I found what I thought was the pressure switch at the front of the vehicle behind the radiator grill. I was assuming the little radiator at the right side of the engine radiator was the condensor, although that is the inter cooler eh?

Anyway, I bridged the pressure switch and that's definitely the problem, all working fine now. I'm nearly 100% it's just faulty too because it was cutting the air con out even on a cold start (so not due to icing up), and then come back on, then off, then on again. I imagine if the evaporator was icing up I would end up with a puddle of water on the passenger side floor?

I've left the bridge in for now because I want to take it for a decent drive and make sure all is ok. I'll keep the thermo turned right down. Can I do any damage or is it likely to be ok? Will be taking it to have it replaced tomorrow if I can find a fridgy open. I assume I need an air con guy, not an auto elec?

The last two photos are of the pressure switch and the two wires going into it.

My next question is where would the condenser radiator be and should it have an electric fan? Unless it's in behind the radiator shroud and I can't see it from from the grill? (please forgive my ignorance if I'm way off course :-()







http://i1041.photobucket.com/albums/b413/fender222/defender%20air%20con/aircon6.jpg
http://i1041.photobucket.com/albums/b413/fender222/defender%20air%20con/aircon5.jpg
http://i1041.photobucket.com/albums/b413/fender222/defender%20air%20con/aircon4.jpg
http://i1041.photobucket.com/albums/b413/fender222/defender%20air%20con/aircon3.jpg
http://i1041.photobucket.com/albums/b413/fender222/defender%20air%20con/aircon2.jpg
http://i1041.photobucket.com/albums/b413/fender222/defender%20air%20con/aircon1.jpg

[Blknight.aus]

warning lights are on......

somethings not jelling with what I remember about the deefer AC

Dont waste your money on anything Ive got to have a think about it... it sounds like its gassed wrong.

[fender22]

Didn't bloody fix it as it turned out. 10 mins down the road and did the same thing. On for ten minutes, off for 10 minutes.

One thing I did notice today was that the 3spd switch at the back was getting warm near the black wire terminal.

[bee utey]

Sounds suspiciously like a loose/hot running terminal somewhere. Clean and tighten any terminal you can find. Install a relay so the compressor clutch doesn't load up the circuit, ie use the compressor wire to switch a relay that takes its power from the battery or other major battery circuit. I have done this mod on a number of older style a/c's which have the compressor switched by the thermostat directly. Quick to do.

[fender22]

Trouble is I don't know where they've put the relay and thermo amp? Best I can tell it must be behind the under dash unit somewhere. Its not in the battery well

[fender22]

Is there a permanent positive wire under the bonnet somewhere I can get a feed off?
The relay idea sounds good, save loading up the whole thermostat circuit. I'll switch the relay with the feed wire to the compressor. The guage of the cable to the compressor is quite light actually? Would have thought it would be a considerable load to pull the clutch in

[slug_burner]

Is there a permanent positive wire under the bonnet somewhere I can get a feed off?
The relay idea sounds good, save loading up the whole thermostat circuit. I'll switch the relay with the feed wire to the compressor. The guage of the cable to the compressor is quite light actually? Would have thought it would be a considerable load to pull the clutch in

The starter motor will have a permanent positive on one side of the solenoid.

[Blknight.aus]

ditto for the alternator.

[isuzu110]

Is anyone familiar with the characteristics of the temperature probe leading to the thermo amp ? Does it go open circuit when it gets cold or does it conduct more when it get's cold ?

What would happen if i shorted the wires to the probe ? Would the aircon not start or would it not turn off until the pressure switches cut in ?

Could shorting the probe temporarily damage anything ?

[isuzu110]

*bump*


Is anyone familiar with the characteristics of the temperature probe leading to the thermo amp ? Does it go open circuit when it gets cold or does it conduct more when it get's cold ?

What would happen if i shorted the wires to the probe ? Would the aircon not start or would it not turn off until the pressure switches cut in ?

Could shorting the probe temporarily damage anything ?

[Davehoos]

nornally if you short the two wires on the thermister the op amp turns on.
its a balanced setup comparing the resistance greated voltage in the temp pot and normally wont damage anything.
its ony a small voltage.to test.less than 5V.

i cant see the photos so im guessing its a plastic case under dash unit.
with the deisel defender the temp amp is under the seat and has a temp adjust screw and some inline fuses.

i found these on both sides of the car depending on battery or model.
think they a dirty green.

the fan switches are common cheep and melt easy.best to run relay for each speed.

pressure switch normally in series with the clutch.
normally clutches draw very low amps and melt down before blowing a fuse.most genuine land rover systems dont supply enough volts to the clutch when it starts to wear it often wont engage as the under bonnet heat rises and the clutch requires reshim.

[Davehoos]

once had a problem with a vehicle with 2 batteries.

the power was conected to one and the earth on the other.when the voltage control circuit switched off the a/c cross fed and caught fire.

[isuzu110]

Thanks for the notes

Here's what I know so far:

Thermo amp under passenger seat is marked Genelco 14-995S 3649 28(5)F

Has a potentiometer undeneath tehrmo amp allowing adjustment of reference temperature. It is marked (C)old on one extreme and (W)arm on the other. Mine was set a 2/3 towards the cold end.

8 way connector to thermo amp under passenger seat had wires:

Green - Earth
Black - Clutch/Pressure Sw
Red = +12V
Blue - Earth
Yellow - Temp setting Potentiometer on dash
Yellow - ditto
Grey - Temp probe on evaporator
Grey - Temp probe on evaporator

Temp probe was giving ~5.6K Ohm across probe when disconnected from thermo amp at room temp. The hotter the ambient temp, the lower the ohms from the probe.

Temp setting pot on dash seems to range from ~10K on warm to 15 ohm when on cold.

My aircon runs for 10min and then clutch on compressor disengages yet there is power coming from thermo amp red wire. There is no power reaching downstream pressure switch. I suspect there is some fault (relay) in between thermo amp and pressure switch.

Still investigating

[Ratel10mm]

So if the thermostat is giving you a call for cooling, but the compressor isn't engaging then it's most likely one of the safeties is tripped. I don'tknow my way around vehicle a/c, but the stuff I work on will have a high pressure switch, often a low pressure switch, ditto a motor overheat protection device (commonly referred to as a 'klixon' in my trade), fuse(s) & some other stuff like overloads which won't be on car a/c as it's powered by the engine.
Of course, you could just have a loose connection somewhere.

If you can find a wiring diagram, that'd be a big help to determine the possible fault.

[isuzu110]

Here's a wiring diagram from elsewhere on this site

https://www.aulro.com/afvb/

[isuzu110]

Here's a wiring diagram from elsewhere on this site

http://www.aulro.com/afvb/attachments/90-110-130-defender-county/31916d1292805913-air-con-wiring-advice-needed-photo.jpg

https://www.aulro.com/afvb/images/imported/2015/09/763.jpg

It shows only one pressure switch between the thermo amp and the clutch. I can see a pressure switch on top of the receiver-dryer and that has no power to it, even though the wire feeding it from the thermo amp is live. Has anyone seen a second pressure switch in series in the circuit or a relay between the thermo amp and receiver-dryer pressure switch ?

[Ratel10mm]

Ok, it looks to me as though the double rectangle shape on the cable from the thermo-amp to the pressure switch designates a plugor other connector. If you have a signal leaving the thermo-amp but nothing at the feed to the pressure switch, then the first thing to check is that connector.

[isuzu110]

Yes - I've already checked the connector and no power.

Next thing is to run a new wire from the thermo amp to the receiver dryer pressure switch and hope I bypass the problem. Hopefully I'm not bypassing another hidden hi/lo pressure switch and there's just the one of them.

[isuzu110]

Ok, I think I have this one...

Looks like the output relay on the thermo-amp circuit board is dodgy. The relay clicks OK, but the contact doesn't make properly- hence intermittent voltage to the pressure switch and compressor clutch. If you tap the relay when it is energised, the contact finally makes. I suppose this relay has cycled many times since the vehicle was made in 1985.

The thermo-amp manufacturer Genelco seems to have been bought out by another US company Arizona Instruments in the late 80s. AZIC don't seem to manufacture the thermo-amp any longer.

The relay is manufactured by Sky Electronics in Georgia, but I am yet to find an Australian distributor for them. The pin-out of the relay (CKC-1C) seems somewhat unique to this manufacturer.

I may need to remotely mount a replacement relay off the PC board.

[isuzu110]

Yeah guys, sorry if this bores you....

If your 300tdi Defender aircon stops working after a few minutes even though it's all gassed up, check the blue relay inside the thermoamp box is actually switching despite making a clicking noise. I suspect the contact rating may be marginal for the application. A simple way for me to test this was tapping the thermoamp box and hearing the compressor clutch kick in.

The specs for the orginal relay are here http://www.sourceresearch.com/sky/sky-pdf.cfm?PdfPage=CKC.pdf

I've removed the offending relay from the printed curcuit board on the thermo amp. I was hard pressed finding a replacement that only had a coil current draw of 30mA and was worried a relay with a larger coil current may have damaged the driving transistors.

I ended up going a bit overkill and buying a kit from Jaycar DC Relay Switch Kit - Jaycar Electronics (http://www.jaycar.com.au/productView.asp?ID=KC5434&keywords=relay&form=KEYWORD) that draws a very low current and is opto isolated from the switching thermoamp. The relay is rated at 30A - way overkill.

All good so far.

[Ratel10mm]

Good news. Congrat's on the fix. :)

[Davehoos]

common fault over time.also cracked older joints.

sometimes its can be caused by the current draw on the clutch coil.
normally these draw 2-3 amps.when hot it can go up to 5 amp and when the fan starts to draw current the voltage drops raising the current needed to pull in the clutch coil.

the power is supplied to the clutch from the same fuse as the blower fan.
you can electrically melt the clutch coil before the fuse blows.

worth fitting a 7.5-10 amp quick blow [spade] fuse to the circuit before or after the pressure switch or a relay with fusedirectly from battery 12 volts. .