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2006 Sierra 1500 2wd 4.8L A/C Low side port has very high pressure


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I have a 2006 Sierra 1500 2wd 4.8L and the A/C which was working last summer is not working this summer. Compressor cycles on and off continuously when calling for cold (only 2 or 3 seconds on, then shuts off). I thought possibly it was low on refrigerant (R134a) but when I applied the gauge to the low side port, it climbed rapidly into the "warning" area on the gauge. (Over 500psi)

 

How do I troubleshoot what the problem might be?

 

Thanks for your help,

Dave

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Is the A/C set to max with all windows/doors closed? If yes and still getting the high pressure warning then you probably will need to get some refrigerant out. It may be cycling rapidly from the high pressure cut out. You will need to take it to a shop where they can remove the excess refrigerant the safe way.

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Did you ad refrigerant or this is what you found when you were about to ad some? What is the suction side showing when this is happening? If your lucky, your overcharged...

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The system was working last summer, none has been added since. I applied gauge to check pressure expecting it to be low, it was very high. Also of note, the pressure reading was over 500kPa, not PSI as originally posted.

 

06SierraZ71, the A/C was set to high/max when tested. Window was open. Does that really matter?

 

chupe442, How do I check the suction side? Gauge applied to the low side port as instructed. Is this the equivalent of the suction side?

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That's 72.5 psi. You could have a low charge or bad cycling switch

 

The low side psi will drop when the compressor is on and rise when off. What is the cycling psi range? It would be better if you had actual AC gauges on the system to better read and diagnose the system

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That's 72.5 psi. You could have a low charge or bad cycling switch

 

The low side psi will drop when the compressor is on and rise when off. What is the cycling psi range? It would be better if you had actual AC gauges on the system to better read and diagnose the system

+1 need to take low side reading with compressor running. Usually fast cycling means its low on refrigerant.

 

Sent from my LGL86C using Tapatalk

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I mis read/understood your post. Sorry. 500 psi got me and took it for a high head side read. Carry on....

 

 

I agree with txab.. Get some proper gauges. Those single gauge one shots are nice until you have to diagnose what is happening..

 

 

Good luck!

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Indeed it was fast cycling due to low refrigerant. High pressure reading was maxing out gauge so I disconnected it. When leaving it in place, the low side of the cycle did indicate low refrigerant. Added some and all is well.

 

Thanks for the help.

 

Dave

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