Hey everyone!

I've been trying to diagnose no a/c in my '91 Chevy C2500. The a/c light flashes for two minutes and the compressor never kicks on.

Here's what I've found:

-Fuse is good.
-Relay is good.
-Clutch engaged when power jumpered to it, but squealed very loudly.
-Jumpered low pressure switch and clutch still didn't engage.
-Gauge shows refrigerant is good charge.

What am I overlooking? Thanks!

 

May be the control unit itself is bad good luck finding one though 91-93 are the same only 94 was different and 1995-2000 went to the dial type, I just redone mine with new compressor, condenser coil, receiver/drier and condesate line< this was available at G.M. Parts now for $120 picked mine up at the dealer for$58 and it was 95* sunny in a black truck and going down the road it was 36* out the vents.