My compressor clutch isn't engauging. I've gone through the process discribed in the shop manual to troubleshoot the problem, and when I got to testing the compressor relay, I got some confusing evidence that it's the cause. When I hook power up to the a and b terminal, I can hear the relay click. But when I hook it up completely and measure the voltages, the wires carrying power into the relay show battery voltage. Likewise, the wire on the permanant circuit side shows battery voltage. The wire on the switched circuit side, though, shows zero voltage. So the click makes it seem like the relay is fine, the voltage doesn't. Does anyone have an opinion on this? BTW, everything after this step in the troubleshooting guide checks out for sure, so I'm really suspecting the relay, but need a second opinion.

 

Crap. I swapped in a known good relay. Still didn't work. I don't understand? Good relay on there, and the compressor doesn't turn on. Jumper on there and the compressor does turn on. Where's the difference? It can't be a critical value, the thing's getting 14 volts from all directions.

 

There are sensors in the A/C system that detect if the compressed refrigerant has a high/low pressure. This could be the reason your clutch isn't coming on... If your refrigerant is low, then add some and it should come on automatically.

Later