The air conditioning in my S80 is out. I turn on the system, and the compressor clutch does not engage. It’s almost certainly a leak, but I want to check the wiring before buying a manifold gauge set. Below is the pertinent section of the wiring diagram.

The important components are...

  • 2/22 Relay
  • 8/3 Compressor

When I turn on the ignition without starting and jump terminals 3 and 5 on the relay, the clutch engages; that part works as it should. I also pulled the relay and verified it works.

With the car on and the air conditioning switch on, terminals 2 and 3 light up a test light. Terminal 1 does not.

I think this all points to the ECM not sending a signal to engage the clutch. Am I missing something?