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Compressor spins but not cold

Icebrand on Sat May 03, 2014 5:43 PM User is offline

Year: 2000
Make: Chevrolet
Model: Corvette
Engine Size: 5.7L
Refrigerant Type: R134
Ambient Temp: N/A
Pressure Low: 35
Pressure High: ?
Country of Origin: United States


When I got the car it hadn't been driven much within the previous 2 years or so. A/C System blew cold for a couple of weeks until it got warm. Filled the system, made it cold, slowly got warm again. Decided messing with it too much wasn't in the budget at that point.

Today I injected some dye and filled the low side to 24-26 PSI, now 35 psi with the warmer weather and turned the system on. Pressure on the low side never changed. I'm assuming the high side is not pressurizing. Compressor turns on and spins, no screeching. Air is still warm. Reset my DTC codes. No change. Could it be a stuck valve?

mk378 on Sat May 03, 2014 6:55 PM User is offline

It is a variable compressor system. The design of the compressor will hold the low side pressure right at 25 throughout a wide range of operating conditions, both normal and abnormal. Even moreso than other systems, charging by weight is the only way to be sure of a proper charge. In order to do any diagnosis, one must be able to measure both pressures.

If you only have 35 with the compressor off, there is practically no refrigerant in it. Look for leakage from the seam between the front and back halves of the compressor case. Such "belly leaks" are common.

Edited: Sat May 03, 2014 at 6:57 PM by mk378

Icebrand on Sat May 03, 2014 7:07 PM User is offline

Thank you for your quick reply. I'll jack the car up, look for a leak, and get back to you.

Icebrand on Sat May 03, 2014 7:34 PM User is offline

Okay, I looked around the belly of the compressor and the input/output lines and I didn't see anything that looked like the fluorescing dye I injected on the low side. There was what looked like semi-fluorescent dirt in between the front and back parts of the compressor, although it was faint. Is the next step to figure out what the high-side pressure is at?

mk378 on Sun May 04, 2014 10:21 AM User is offline

> A/C System blew cold for a couple of weeks until it got warm. Filled the system, made it cold, slowly got warm again.

Clearly there is a leak, so the next step is to find the leak. In order to leak test with dye you need to put in a full charge and run it. Most leaks will only let gas escape while the car is off. With the system running normally, the dye/oil mixture will be flowing around and covering the inside of the leak with dye, which will then leak out and be visible outside. A leak that leaks out in 2 weeks might be better found with an electronic leak detector.

Edited: Sun May 04, 2014 at 10:24 AM by mk378

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