A/C Wiring

I have a 89 Comanche and I need to figure out how to get my compresser to work. I know the compresser works because I jumped it to the battery and works just fine. I need to figure out what to look for in the wiring that would cause the compresser not to work. I checked the fuses and they are good and replaced the four relays that are under the hood. Is there anything else I should be looking for?

After I figure out this fun problem I get to switch the freon over to the new stuff...O joy

The ECU controls the compressor. To do this it looks at a temp switch in the evaporator housing and a pressure switch on the container that also houses the sight glass. If the system is extremely low on refridgerant, the pressure switch will be open circuit and the compressor will never run. The temp switch in the evaporator is to prevent icing. If too cold, it will also be open circuit.

Thanks PaulJ

That sound like it makes sence. The sight glass is clear so Im guessing that all the gass is gone. Thanks again...Randy