Hi Thom, I don't have a schematic beside me but the clutch cycling switch is on the accumulator; there should be 12V + on one side when it's unplugged and voltage on both sides when it's plugged in. The compressor clutch field coil is down there on the compressor, natch, you should check both sides of the plug for 12V+ and a good ground on the other wire. If you've got juice to the clutch but it's still not engaging I would give it a little tap with a long screwdriver (the outside front part that's not turning) but be prepared for it to start turning when you give it the tap! If that happens then it means that the clutch has worn out enough so that the air gap is too much for the field coil to pull in the outer part (the shoe). The quick fix is to pull off the shoe and remove one of the shims that create the air gap. If you don't have 12V+ at the clutch cycling switch then the problem is likely in the HVAC controls, a fuse or a relay. Since I don't have the electrical drawing at hand I can't help you there today. I recommend that you use a 12V test light for the electrical tests, not a multi meter. Meters will show a voltage but it may be a 'ghost', a test light will not light unless there's the current to back it up.Always test both sides of a circuit, 12V+ is great but useless if the ground wire on the other side of the circuit is broken. To test for 12V+ attach the alligator clip of the test light to the engine block or the negative battery terminal and probe the switch for the + voltage. To check grounds attach the alligator clip to the positive battery terminal.