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A weak compressor?

70rustrunner on Sat March 23, 2013 9:07 PM User is offline

Year: 1992
Make: Chevrolet
Model: Camaro
Engine Size: 350
Refrigerant Type: R134A
Ambient Temp: 60
Pressure Low: 40
Pressure High: 150
Country of Origin: United States

Replaced the engine in the car about six months ago. Disconnected the hose fitting at the compressor at that time and reconnected it after putting in the new engine. Went to refill the system today. Pulled a vacuum for 30 minutes and it pulled down good and held vacuum. Then charged the system with the 2.25 lbs it called for. The compressor runs about 80% of the time and only builds up to 200 psi at the end of a cycle and the needle on the gage fluctuates a small amount. The system was running good previously. It does blow cold though. Could I have a weak compressor?

GM Tech on Sun March 24, 2013 7:51 AM User is offline

Only 200? at 60 psi ambient? That's pretty darn good- low side is cycling- what more do you want?-- when it is hot out, that pressure will be more like 250- 275- it is all temperature dependent.--

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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......

mk378 on Sun March 24, 2013 8:08 PM User is offline

Sounds like normal operation.

On cars that have electric fans you can test the compressor by disconnecting the fans, you should get 400+ psi high side. Hope the HPCO switch works.

70rustrunner on Sun March 24, 2013 10:33 PM User is offline

Thanks for the assistance. Glad to hear that the readings are about normal. Guess I am just to used to working on cars on 100 degree days.

NickD on Mon March 25, 2013 12:20 PM User is offline

Key reason why practically all manufacturers recommend charging by weight. Even if you were to have a sight glass, ran your engine at 2,000 rpm, blower at max, doors open, will see plenty of bubbles in that sight glass at 60*F. If charging by pressures, or even checking them, best done at a 85*F + day.

Still don't know why they automatically switch on the AC in the defrost mode on a 35*F day, doesn't do anything except wear out the compressor. With tiny engine cars like my Cavalier or Cruze, not even sure why they have a radiator fan, hardly ever comes on at all.

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