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2001 Chevy Silverado

Over the months I've noticed the AC getting warmer and warmer. Now it is barely colder than outside (which is about 100f).

Details:

Compressor cycles on/off; about 3 seconds on and 7 seconds off.

I have attached a recharge can to the low side plug. The gauge reads~100 PSI (truck is at ambient temp which is ~65f).

I have parts in the mail to convert my R12 manifold gauge to R134a connectors. I have no high side PSI value at this time.

 

With recharge can connected to low side valve and with the truck running with max ac (again ambient temp at 65f):

When the compressor engages, the low side gauge goes from 100 PSI to 5 PSI in a matter of 3 to 4 seconds. The compressor disengages.

At this time, the low side PSI slowly raises back up to 100 PSI which restarts the compressor shortly after and the cycle goes on...

 

Any takers on helping me or giving me possible causes (and what to do about them)?

 

I have a nagging suspicion that someone slapped a recharge can on it and overfilled it. This vehicle is driven by 5 different people; no one fessed up so far... Have to wait for parts to test high side PSI. But I'm also worried that the low side pressure dropped so fast; I feel this is not normal?

 

Thanks for the help!

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whats the psi supposed to be according to the recharge can? If its over pressure just purge some out using a small pick or a small flat head screwdriver and purge from low psi port...(be careful though).

Also, there might be a leak. is it holding pressure continuously? 

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Low on Freon. Slowly getting warmer is a sign of a leak.

Static pressure for r134 would be 70-100 for temps in the 50-100F.

When operating normally, low would drop to around 30/35 and high would be 250-350 (depending on temps, humidity etc).

Low pressure dropping to 5 would trip the low pressure switch and shut off the compressor. Once static pressure rises above the low pressure switch limit, compressor comes back on.

Do NOT rely on recharge can change for proper fill as a wide variability of measuring could lead one to over fill and blow the compressor.

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I think I'm a complete fool... After watching some youtube vids, I figured out that the gauge on the can is only valid if the compressor is running. I will buy another recharge can tonight and charge it until the low side pressure is ~30 PSI while the compressor is running... 

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