A/C clutch isn't operating.
Jumper between 30 and 87 at the relay does not activate clutch. 30 confirmed hot.
Manual says 86 should be hot when ignition switch is in the "on" position- it is not, but coil ground (85) is now hot when it's not when the key is off.
Shouldn't 85 be grounded with the engine running and a/c turned on? Bad PCM?

I thought I could get the electromagnet to engage by jumping power and ground to the clutch, but no go there either- but perhaps it needs the pressure switch to do so (?).

 

Truck info would be nice. Terminal 30 should be hot key on or off, You need to jump power to 87. If it doesn't work check the coil and see if you have any resistance. None, It's bad. Assuming you have a good ground to the coil.

 

Sorry- 2000, 2500, 5.9 gas

30 is hot key on or off, but jumping to 87 does nothing.

There's a black wire, and black w/ white stripe. Which is the ground? I can't find a schematic for the connector/harness.
If ground is confirmed good, time for a new compressor?

 

If you jumper the clutch wire at compressor, pressure switch is irrelevant. It should engage.

What if you jumper then knock it back manually? If this works, gap has grown too large.

I fixed a '99 1500 by removing the lone shim.

 

The coil is grounded at the compressor. Check you have power going to it at the compressor plug. You can replace the coil, You don't have to buy a new compressor.