The first thing I'd do is swap the AC compressor relay with a different one like it to see if the contacts are arced or burned causing an intermittent problem. Chances are pretty good that's not going to help but lets not overlook something simple.
The next thing is to bypass the pressure transducer with a jumper wire. A small paper clip or piece of wire will work but be careful with the terminals in the connector because they can be spread easily. If this problem is intermittent you have to do this test while the problem is acting up. It won't mean anything if you do it while the system is already working normally. If the problem clears up when the transducer is bypassed, either the system is low on charge, over-charged, or the transducer is defective.
The next potential cause is an intermittent contact on the thermal limiter switch. That is built into the compressor. To identify that you would have to monitor the compressor relay with a test light or voltmeter, and monitor the voltage at the compressor clutch at the same time. Both should have 12 volts at the same time. If there's 12 volts coming from the relay but 0 volts at the clutch when it it kicks out, the thermal limiter switch is defective. To replace that requires the replacement of the compressor.
The electric clutches have a rather high failure rate too but I don't think they are typically intermittent. If you find voltage at its electrical connector but the clutch still kicks out, it is defective. Those can be replaced without replacing the entire compressor.
Wednesday, September 19th, 2012 AT 1:37 AM