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AC System 1998 Buick Regal

This AC system was professionally diagnosed as having a faulty compressor last fall. A new compressor and drier has been professionally installed, the system flushed, new orifice tube, etc., and recharged. After all that time and expense, the same original problem persists. The system cycles at will with no clear pattern. It can blow cold air for hours or not work for hours.

So I purchased manifold gauges which check the high and low sides. When the compressor is running, the readings are good BUT, when it is not, the high side is low and the low side is high. I can?t believe the R134 is low if it functions well sporadically.

So my question is?.. does this sound like an electrical issue? Is it safe to short-circuit the compressor with a switch since the car is so old? Could the compressor freeze up and ruin the belt if it is hooked up direct?

Any assistance would be appreciated but please don?t tell me to consult a professional— I?ve already done that and all they have done is harvested my money.

I’d pull the orifice tube, and check to see if the screen on the orifice tube has collected debris that was missed when the system was flushed.

Tester

Does the system have to be evacuated to accomplish that?

The refrigerant needs to be reclaimed, and after checking the orifice tube, the system needs to be evacuated to remove air/moisture before recharging the system with refrigerant.

Tester

Something a little easier (and doesn’t cause you to loose your charge) is replacing the low pressure cycling switch along side the accumulator. We did these on GM’s of your era without any other diagnosis,just unscrew old,screw on new. It was the culprit many times.

Just being curious here, but exactly what are those high and low side readings with the compressor engaged?

As to this oddity, what are the high/low pressures when the compressor is not engaged?
The pressures should stabilize when the compressor is not engaged and both should be the same.

Just offhand, I’m inclined to agree that the low pressure switch could be acting up but many times people post on this board about certain pressures being correct when they’re not, so I just wanted to clear that up.

The pressures were 50 low, and 250 high when the compressor was kicked in and was blowing cold air. When it disengaged, the low side red-lined. I would have to retest for the high side at that point. I appreciate your response… Mark

I would be willing to just replace it if it is not terribly expensive. I will try to locate it. Thanks very much for taking the time to reply… Mark