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Compressor Operation: Ambient Temp

Dave in Texas on Mon November 02, 2009 9:12 AM User is offlineView users profile

This question concerns late-model GM products. What ambient temp will cause the compressor to not activate? My R12 system has to be 40Fdg/higher to activate compressor. Is that temp lower for the later/newer 134 systems? Just curious, have no trouble. Thanks

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At 2, I went home with a 10. At 10 I woke up with a 2 !!

Chick on Mon November 02, 2009 5:56 PM User is offlineView users profile

Not knowing which GM car you have, I would say thats about right. As the engine bay warms up, the compresor will still come to help with the defrost (Removal of humidity) but only when the refrigerant temps (pressures) get high enough..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

JACK ADAMS on Mon November 02, 2009 6:21 PM User is offline

Either way, most GM cars/trucks that use a cycling switch will cycle off at 22psi on the low side.

Dave in Texas on Mon November 02, 2009 6:33 PM User is offlineView users profile

Not my car...converted it to 134 back in the mid-90s. Thanks. A guy turned his 2000 DeVille Off and it would not come back on. He's in cold country so I took a guess at it since he claims it full of 134.....

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At 2, I went home with a 10. At 10 I woke up with a 2 !!

Chick on Mon November 02, 2009 9:54 PM User is offlineView users profile

If it gets to cold, the compressor would get slugged with liquid refrigerant, so on that car, it is designed not to come below 40 degrees.. all is well..... hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

GM Tech on Tue November 03, 2009 9:09 AM User is offline

If you have an Outside temp sensor- or automatic climate control- that is the trigger for a/c--- a/c is disabled below 40 degf

If strictly a manual system, then system pressure determines the a/c enable-- if above 47 psi (cycling switch activation- or pressure tranducer reading- for a variable compressor system) then yes a/c is on, if below, then it may come on once, then be disabled the restof journey-- all depends on underhood temps, which influence system pressure.....

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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......

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