1985-1998 [Subscribe to Daily Digest] |
I wonder how you can hear the compressor kick in at speed. If sitting at the traffic lights, yes you will. But I have never once been able to notice the AC coming on while driving along.
There are several possibilities for this behaviour. Roughly either your ACC unit fails, or the wiring to the AC relay picks up 12v intermittantly, or your AC rely itself is kaputt.
If I'm not mistaken on your car the AC relay gets its 12v from pin #23 on the back of the ACC unit in the dash. The unit differs a bit from year to year, so if someone knows for sure for a '91 please tell.
You could test the ACC computer by disconnecting the unit and drive around. If the AC stops working completely, you can be sure the computer is the culprit, which is big money.
If the AC keeps on working now and then, look for 12v along the wires to the relay. So take out the multimeter and start searching for a 12v that shouldn't be there. I find the connectors at the anti-frost switch on top of the evaporator always a convenient point to monitor the current for the AC. Basically the 12v from the ACC unit goes to the relay passing two switches in series, being the anti-frost switch (which will open to prevent the evaporator from freezing up) and the pressure switch on the receiver/ dryer (which will open when system pressure is out of range, e.g. low charge).
if there is 12v sometimes, you have an intermittent short in a wiring harness , which is no big fun either.
So in this instance let's hope it's the most likely suspect: the relay. Not sure where is is on a '91, most likely behind the glovebox. On my MY95 it is in the engine bay box, but that car has a passenger airbag. It's a silver-colored relay
You might want to open the relay and check the soldering. Replacing is about $60 IIRC.
Good luck,
Jan Geert
posted by 145.7.20...
, Tue, 4 Nov 2003 13:36:15
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