AC Compressor Not engaging
 

I have an 87 924S. The AC clutch burned up recently. Pretty catastrophic, the magnetic coil overheated and melted the resin that keeps it all nicely coiled.
Any way I replaced the clutch but it will not engage. I have jumped the low pressure switch checked the fuse and tested the AC Relay but still do not get power to the wire running to the clutch. I think it is possible that something else could have been damaged when the clutch coil shorted but I am at a loss what to check next.

You do have freon in it dont you?

Oh, yeah. I have a set of guages connected. If I run a 12v line from the battery to the compressor it engages and cools the cabin.

Putting 12V direct to the clutch and getting it to engage rules out the clutch; sounds like you toasted the A/C relay when the clutch seized/melted. Most likely in my mind.

Other possibility is the low pressure switch got toasted too, but not as likely as A/C relay above.

When my clutch shorted to ground it burned a trace on the a/c amplifier board. It's under the passenger side kick panel to the right of the glove box. In 1983 they were black and about the same size as a note card or 3x5. Take it out, open it up and look at the back of it. The power goes from the amplifier to the low pressure switch and then on to the compressor. If everything else checked out, that's my bet.

I soldiered in a jumper wire, works great now.

Oh, relay #3 is not for the a/c, the a/c relay and condersor fan (a/c) relay is over there with the amplifier. You'll see them when you get after it.