LOW PRESSURE ON HIGH SIDE OF A/C SYSTEM

  • Tiny
  • jarhead1987
  • 2002 Chevrolet S-10

Working on 2002 chevy s10 with 2.2 liter engine.
I replace the a/c compressor and accumulator. I filled the aftermarket compressor with 8oz of PAG per the manufacturers specs. I flushed the system pretty well with an approved a/c flush. I evacuated the system down to 30 in/hg and it held steady for over five minutes. I put in about 2 1/2 cans of R-134a. The static pressure on the high and low sides are what they should be for the ambient temperature, low 110psi, high 115psi. When I start the truck up and turn the a/c on high the low side measures 45 psi and the high side stays at 115psi. Mfg specs call out for 41-49psi low side and 245-285psi on the high side at the current temperature and humidity level. At 95 degrees ambient temperature, the a/c was putting out 60 degrees. Everything seems to be functioning fine except for the low pressure on the high side.

What could be causing the high pressure side to be low by over 130psi?

Thanks.

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Sunday, July 17th, 2011 AT 1:20 AM

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  • Tiny
  • ASEMaster6371
  • Expert
  • 25,556 posts

Low side is a little high. Should be about 25-30. My concern is you put in around? 2 1/2 cans? It needs to be exact to work well. At 95 high side should be around 250. The formula is twice the outside temp plus 10%. I think you have too much freon in the system.

Roy

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Sunday, July 17th, 2011 AT 1:26 AM
  • Tiny
  • jarhead1987
  • Member

I pulled the specs from a factory service manual. I filled the system until the low side was at 45psi. The specs call out for 1.75 pounds of R-134.

I think you might be right about too much refrigerant. I was watching both sides of the gauges as I was charging the system and the high side never went above 110psi.

I will try bleeding some off and see how that works.

Where did you get the low side values from?

Thanks for your help.

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Sunday, July 17th, 2011 AT 1:38 AM
  • Tiny
  • ASEMaster6371
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Pressure readings are never indications of freon level.
I am a technical instructor and it came right from the book. 1.75 lbs means exactly that, no more, no less.

Roy

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Sunday, July 17th, 2011 AT 2:37 AM
  • Tiny
  • jarhead1987
  • Member

I think the compressor is defective. After just a few minutes it gets extremely hot. It was a brand new aftermarket unit.

Thanks for your time.

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Sunday, July 17th, 2011 AT 2:41 AM
  • Tiny
  • ASEMaster6371
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Good luck

Roy

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Tuesday, August 16th, 2011 AT 11:16 PM

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