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High Side Pressure fluctuating

penningp on Tue June 15, 2010 1:30 PM User is offline

Year: 1994
Make: Chevy
Model: Silverado
Engine Size: 6.5 L
Refrigerant Type: R134A
Ambient Temp: 90
Pressure Low: 45
Pressure High: 200
Country of Origin: United States

Hello all,

Got some ac issues I hope someone can help with. I just fixed my ac system - new dryer, new orfice tube, vaccumed down the system and recharged it.

When installing the new condensor and attaching the lower line (where the freon hits the orfice tube) we accidently twisted the tube coming out of the condensor and sort of crimped it. We were able to uncrimp it mostly.

So - on to my issues:

1) when idling the truck does not blow cold air or even cool air - it blows about 80 degrees - is this the sign of a weak compressor? when the truck is moving the air blows at about 60 degrees.

2) With the gauges hooked up and the truck idling the high side gauge fluctuates about 30 psi rapidly (the guage fluctuates around 200 psi)- the low side stays at about 50psi and is stable. Is this a reaction to the crimped condensor tube or is this an issue with the compressor - or both??

The truck is on 134A.

Thanks for the help,


mk378 on Tue June 15, 2010 2:31 PM User is offline

Do you have the proper full charge by weight in? What you describe seems typical of having poor condenser airflow (worn out fan clutch) leading to undercharging trying to keep the high side pressure down.

GM Tech on Tue June 15, 2010 3:22 PM User is offline

Hope you plumbed it correctly-- those c/k trucks can have the condenser connections reversed very easily since they use the same threads on both connectors.....compressor should feed the top of condenser-always....

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......

penningp on Tue June 15, 2010 3:32 PM User is offline

Yep - the compressor feeds the top of the condensor.

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