Automotive Air Conditioning Information Forum (Archives)

94GTP on Thu September 02, 2010 6:22 PM

Year: 1994
Make: Pontiac
Model: Grand Prix GTP
Engine Size: 3.4l
Refrigerant Type: r134a

So it is hot as hell outside so I figured I would try and get the ac to work. Checked all the relays because the clutch wouldn't engage and they were fine. So I connected my actron cp9145 and it was showing ac pressure as 5 psi. So I added more freon to the system and the pressure went up and kicked on the cluch. So I thought I was set, wrong. Everything test fine with the car in run not started but as soon as I start it the cp9145 shows the clutch is enabled, the ac not active, the ac pressure as 111 psi, and the ac request is yes. As soon as I shut off the car everything stays about the same except the ac is active. I would have thought it would be the other way around. Any ideas on why the system is not active as soon as I start it? Thanks

GM Tech on Thu September 02, 2010 6:33 PM

Power steering pressure switches were a major fault on that model/year.... simply unplug it to test-- it is on driver's side behind wheel on steering rack.

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

94GTP on Thu September 02, 2010 7:00 PM

Thanks, I'll try that this weekend.