82 300SD - AC system is charged, compressor/clutch runs OK when 12 V put across it (you could kill a penguin with how cold it blows, so that's OK), but the AC clutch refuses to kick on under normal operating conditions. I've tried jumpering the pressure switch and the temp switch (maybe do both at the same time?)

Is there any other thing that might be funky, like a relay?

How about voltage checks on the wires to the switches. What wires should have what voltages? Fuses look OK.

Any other diagnostics to try? It's driving me nuts being out of whack like this, and I want it back in whack ASAP with the hot weather coming on. Even a (safe) workaround would be acceptable.