To check the compressor clutch operation.

First check low pressure switch. The one without wires coming out of the switch, just 2 spade connectors. If you have 12Vdc on one leg and not the other you may have a bad switch or most likely low freon. Jump the 2 connectors together and see if the compressor comes on if it does then check freon pressure. If low, charge and check for leaks, if not low then replace switch and recharge system.

Next step if all is ok above;

1. Speed sensor on back of compressor. Should read 0.3v AC with DVM. Can read a little lower such as 0.28Vac and be OK dependant on meter used.

To test; remove AC relay and jumper pins 87 and 15. This will turn on the compressor and keep it on. ( pin 15 )is 12Vdc when ignition is on. Pin 87 goes to compressor.

2. If your car is running correctly and I hope it is Check between TD and 87Z this is the Engine speed signal going to the AC relay. Should read 6Vdc - 8Vdc and will increase when the RPM increases. This is a square wave signal if looked at with a scope.

3. Temperature sensor input this is only a factor if you are using autoAC. Always test AC with max blower and AC dial set to min.

4. Bad connections to the items above. I would suspect the AC relay. Remove the cover and check for bad solder connections. Or replace relay.


Good luck.
Anthony Bridges