97 GMC K1500 XC A/C not working - electrical

[Scrat]

Howdy all,

So last fall when i bought this truck the AC was working fine. Last weekend I went a a trip and the outside temp was hot so i turned on the AC and nothing... fan blowing hot air. I figured it needed to be recharged... no biggie.

Well today i went to charge the system and again nothing. I started checking fuses and relays... all good. I got out my test light and did some checking and stumbled across this...when i touch the test light probe to the 86 prong on the AC relay, the AC clutch engages and the AC system works. I swapped relays with a similar one and same thing happened, so the relay is good.

I keep the system running this way long enough to verify that the coolant charge is fine. This leads me to believe it is an electrical problem (duh). Trouble is the schematics i have available to me suck. It seems like its either a broken ground connection somewhere or the AC control module is going out?

Thought I'd look to the board for wisdom before i go and start tearing into things blindly. So my question is, has any one had this experience before and how was it fixed?

Its getting hot here in AZ and I'd like to get this fixed...

Thanks in advance...
Scrat