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Low side pressure too high...

PCWeber on Mon August 10, 2009 10:57 AM User is offline

Year: 1998
Make: Pontiac
Model: Grand Prix
Engine Size: 3.8L
Refrigerant Type: 134a
Ambient Temp: 90
Pressure Low: 100
Pressure High: 150
Country of Origin: United States

Picked up a 1998 Grand Prix for my daughter last week. AC blew just a bit cold so I assume it needed to be topped off. (Compressor runs fine/ constant while AC is turned on) I put the gauges on and noted the low side reads at around 100psi) If I recall a plugged orifice tube symptom is a very low or negative low side reading. From some searches I have seem recommendations to change the compressor or the refrigerant control valve on the compressor. Does this sound like the direction I should go?

TRB on Mon August 10, 2009 1:04 PM User is offlineView users profile

You need to be sure you have the proper amount of refrigerant in this system, 35 ounces. If you still have odd readings like you have posted I would suspect a bad control valve.


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GM Tech on Mon August 10, 2009 1:53 PM User is offline

Sounds like the pump s not engaging-- is clutch turning? 100 psi is most car's static pressure.... with a hot engine

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......

Edited: Mon August 10, 2009 at 1:54 PM by GM Tech

PCWeber on Mon August 10, 2009 2:37 PM User is offline

yes, compressor is definately turning on with AC turned on and confirmed running by looking at clutch and hearing it click.

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