'90 A/C problem
Thread Starter
Heel & Toe
Joined: Nov 2005
Posts: 22
Likes: 0
From: Florida
'90 A/C problem
I have the climate control system in my Vette. The compressor does not come on when the control is turned or nor when the defroster is turned on. I hot wired the compressor and it runs and the air blows snow. Using the service manual, I tried to get codes out of the control devise; simultaneously pressing the fan up and down arrows, displays the anticipated -0.0, the pressing 'auto' as directed to get the codes, not codes are present. I've jumped the relay by the right exhaust manifold, but the compressor doesn't come on, which, as I understand it, means the relay is fine. I have also swapped the control unit with what I believe is a working unit, replayed the diagnostic process and get the same results. Any ideas??
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Assuming the compressor relay is good, the other possibility is a bad low pressure switch or connection at that switch which is usually wired in series with the Relay. The ECM monitors that circuit for how often it opens and closes and if it does it too rapidly, sets the low gas trouble code. I'd guess something in that circuity is open, so disconnect and reconnect it to see what happens or try holding the connector onto the switch and wriggling it around. Also make sure the switch is closed - should be continuity across it's terminals with the engine off - especially if it's blowing cold. If not, replace it. If the contacts are closed and the compressor doesn't start, I'd scan it and verify the pressure sensor signal (should be about .8 volts) and that the ECM is receiving an a/c request which will show up as a "Yes" in the a/c field.
