Automotive Air Conditioning Information Forum (Archives)

chuckwp on Tue July 24, 2012 8:58 AM

Refrigerant Type: R-134
Ambient Temp: 90
Pressure Low: 3-040
Pressure High: 300-400

Can a defexctive compressor cause excessive (350+ psi) discharge pressure? If so , how. If it is creating pressure it is compressing, right? Normal causes are air in system, no airflow across ccondenser, overcharge, or restriction on high side. Have had a couple of repairs not making sense lately. Good vacuum to insure no air, correct charge, condenser not blocked, fans working, but still poor cooling with low side normal to slightly high, and high side way up there. In sone case had good cooling, but high side going high enough to cut off compressor. These have been an systems using a TXV.

GM Tech on Tue July 24, 2012 9:41 AM

Repairs not making sense leads me to look at recovery tank..is it full of air?-- is auto air bleed hose attached? and valve core depressed- hose attached with proper end on tank? Seen it before- new guy hooks up the tank- forgets to hook up yellow hose, or puts it in backwards where it does not depress the valve core (no depressor in other end of yellow hose)

Measure your tank pressure- separatey-- should not excedd 100psi at 85 degf ambient- after it has sat all night....I've seen tank pressures at 200 psi with no air bleed off hose attached.

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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......

chuckwp on Tue July 24, 2012 7:18 PM

Quote
Originally posted by: GM Tech
Repairs not making sense leads me to look at recovery tank..is it full of air?-- is auto air bleed hose attached? and valve core depressed- hose attached with proper end on tank? Seen it before- new guy hooks up the tank- forgets to hook up yellow hose, or puts it in backwards where it does not depress the valve core (no depressor in other end of yellow hose)



Measure your tank pressure- separatey-- should not excedd 100psi at 85 degf ambient- after it has sat all night....I've seen tank pressures at 200 psi with no air bleed off hose attached.

If you are trying to say that I may be unknowingly charging the system with a recovery tank that is contaminated with air that is not the case. The system was charged from a new 30 lb cylinder. My recovery machine is hooked up correctly, but I see what you are saying and that is a good thing to keep in mind. I think air in the sysem would also greatly dimish cooling and cause gauge needle vibration.