1995 GMC Sonoma pickup. The A/C was working fine then stopped blowing cold
air. I checked and the compressor clutch is not locking on.
There are 3 relays in the glovebox and 3 more out under the hood near the
blower box. Could it be a bad relay? Or is it more likely just low on R-134
and so the pressure switch is preventing the clutch to lock? Any advice on
how to check this out would be appreciated.