Air con wiring advice needed?

fender22 · 18th December 2010, 03:52 PM

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** · 18th December 2010, 06:36 PM

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 · 18th December 2010, 07:41 PM

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

**Don 130** · 18th December 2010, 07:50 PM

AMC Air Con Defender. wiring diagram.jpg
This hasn't saved very well . I'll try to reload it later. Don

fender22 · 18th December 2010, 07:54 PM

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 · 19th December 2010, 07:24 AM

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** · 19th December 2010, 10:40 AM

thread up (Im too lazy to cross load all the f111 pics atm so I'll do AC instead)

**alhedward** · 19th December 2010, 05:23 PM

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** · 19th December 2010, 05:24 PM

recirc only

fender22 · 19th December 2010, 05:34 PM

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?

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