W124 (300E) testin Klima relay?
 

Is there a way to test this relay? I jumped my chum's compressor on his 300E and it seemed to be fine (pressure switch checks out) and the PBU is okay too.

I know the Kilma has to meet a full set of parameters before allowing the comp to run...

You can jump the relay to engage the clutch, just like the fuel pump relay. This just tells you the clutch is capable of working, you still don't definitely know if the relay is good or not, or if one of the parameters are not met or a bad signal. But you do know it's capable of working, so sort of sets your mind at ease on that end of it.
Gilly

The compressor is tired (60psi high side!) but I'm trying to see why it won't come on by itself...