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Re: 88 9000T AC Air Con issues - Long Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Sat, 5 Jul 2008 14:05:59
In Reply to: 88 9000T AC Air Con issues - Long, Shawn C, Sat, 5 Jul 2008 12:24:42 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The first issue is that the '88 was a R-12 system; R-134 didn't come in until 1993. Now, if the system has been changed over to R-134 in the intervening years, it's OK. But if not, you'll get all the wrong pressures with R-134. They are NOT interchangeable without modifying the system.
Yes, there is a relay that drives the AC compressor. The signal starts as a 12 volts signal from the ACC box, through a pressure switch, an anti-freeze thermoswitch, and finally drives the high side of the relay. The relay also gets a signal from the ECU to tell it not to run when the car is first started.
There are a few big problems with just wiring the compressor on. The first is that the pressure switch is there to keep the system OFF if the pressure is too low. Yes, you can run the AC with the pressure low and it will get cold; not as cold as with the proper pressure. But with low pressure, you can damage the compressor. Another problem is that the compressor is designed to cycle on and off - keep it running all the time, and the evaporator will freeze up. When that happens, things won't be cold any more. But the big worry is the compressor lunching itself if the pressure drops.
There are a lot of places to start, but I suggest you start at the pressure switch. It's mounted on the accumulator/dryer, just below the windshield on the right hand (facing forward) side. It has the pressure switch on the side, with four wires. Pin 1 is green/white pins 2, and 3 are yellow/white; pin 4 is just yellow. Pull the connector off and jumper pins 1 and 2 (Green/white on the end, and the yellow/white right next to it). If you start the car and after about 10 seconds the AC compressor kicks in, then the problem is the low pressure switch is telling you that the pressure is low. If it doesn't kick in, measure the voltage on the jumper. If it is 12 volts, the ACC is telling the AC to turn on; if it is zero volts, the ACC isn't sending the signal.
If jumpering doesn't work, you need to move onto the freezeup thermoswtich on the evaporator, and keep tracing it all the way to the relay (in the relay panel under the glovebox).
My guess is that jumpering the low pressure switch will cause the AC to turn on. Now, the switch could be bad. But I'll bet you have the wrong system pressures. You can run the system that way for a short time, but you'll be buying a new compressor pretty quickly. I'm no AC expert, but putting R-134 into an R-12 system won't work, either.
posted by 76.200.21...
, Sat, 5 Jul 2008 14:05:59 <-- Viewing This Message, Sun, 6 Jul 2008 12:17:57
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