Hi folks-- first post-- I'm resurrecting an '85 that had a bad cylinder-- cleaning up years of "work" by others, with a fair number of parts from Roger, (who is great!)- in in buttoning it up the front of the motor I have a mystery lead (original) which is a male spade connector in a square plastic surround coming out of the bundle near right side (cyl 1) water bridge. The other clue is a new wire strung to the A/C compressor clutch all the way back through the firewall, which I suspect means that someone jerry-rigged the A/C to work-- I'll diagnose that shortly-- wiring diagram shows a lead to pin 9 on the 14 pin connector, but also a connection to the idle control valve...??

The compressor has one lead to the clutch, which should be the power, but also another with a ring terminal attached to the screw retaining the power lead. Before the electrical tape fell off, it looks like both of those leads may have been connected to this new wire back through the firewall, but that doesn't make sense since that would have power going to the compressor body, in addition to the clutch..

any insight is appreciated-- thx

 

If your mystery wire is black, it does sound like it is the compressor clutch power.

The clutch has two leads - power and ground. The ground lead is usually terminated in a ring terminal attached to the body of the compressor or to a fastener on the mounting brackets.

 

You might also run across a single mystery wire by the jump post.

It's for triggering the electric fan if you had the towing option (M208) w/automatic (M249).

 

The wire is black-- so I'll go with that-- thanks a bunch

Wally--you have some great stuff on your site, things I definitely want as I move through this project--