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Freon Gauge Fluctuation


FineVisionz

Question

Hello,

 

I have 2003 GMC Senoma ZR5 and the aircondisioning hasn't been very cool so I went out and got some freon, but when I turn on the tuck, put the AC to max, and connect the freon to the low presure line port. The gauge goes up to about 110psi, then the clutch disengages then it lowers to about 17psi in about 3-4 seconds. Then the clutch will engage and it will rise back up to 110psi, then drop, then rise, then drop, ect. The temperature outside is around 85-90 degrees.

 

If you have any ideas on how to fix/explain whats happening, please let me know!

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Assuming you are using the terms "engaging" and "disengaging" correctly you are not connected to low side. Sounds more like the high side.

 

Double check that the port you are connecting to the low side. Do you have a dual gauge set? If so, connect both gauges. Low side should be higher when compressor is not running. And once compressor starts running, it should drop. Low side will never be 110 psi. unless ambient air temp is about 95 degrees F. At that temp, with the engine not running, and sufficient refrigerant present, the pressure on both sides will be approx. 110psi. Once the engine starts and A/C turned on, low side will drop to somewhere near 30psi, and high side will be approx. 2 to 2.5 times ambient air temp. The low side will drop to a point that compressor will disengage, and the two sides will start to equalize. At about 45 psi, the compressor will engage, and low side will drop, high side will rise. If this cycling is happening rapidly, you are low on refrigerant.

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Low pressure? 110psi sounds like you have to high of pressure. I'm pressure sure it's suppose to be lower by quite a bit. I don't remember right off hand but I thought it should be about half of that. You may be over pressurizing the system and it causing the high pressure cut out to disengage the compressor.

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Yes 110psi is high, but the air comming from the air conditioner is still warm. and I am almost positive there hasn't been new freon put in, in a long, long time.

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.

Yes 110psi is high, but the air comming from the air conditioner is still warm. and I am almost positive there hasn't been new freon put in, in a long, long time.

The air is still warm because the compressor isn't staying on long enough to cool because there is too much refrigerant in the system. The high pressure cut out will continue to cut your compressor off until the appropriate pressure is in the system. In really doesn't matter how long it's been since new refrigerant has been added to a system. High pressure is high pressure. Get the pressures corrected then see how the system performs.

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Low pressure? 110psi sounds like you have to high of pressure. I'm pressure sure it's suppose to be lower by quite a bit. I don't remember right off hand but I thought it should be about half of that. You may be over pressurizing the system and it causing the high pressure cut out to disengage the compressor.

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