Question about 1999 GMC Suburban

1 Answer

Air conditioner not cooling

The air coming through is the outside temperature

Here is what I know:

The ac is properly turned on - at least the switches are engaged and lit.

there is pressure in the system

I have topped off the 134a coolant with a kit from an auto parts store. It was not completely empty.

the compessor is turning and the clutch is turning- although the clutch stops and restarts occasionaly

all the fuses are ok

Thanks in advance fro your help.

Kevin

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  • 3 more comments 
  • KPILMAN Jul 25, 2008

    thanks emmwiz - I took your advice - here is what I discovered:



    switching between defrost and back offers no change in the temperature - both are the temp of the outside air. the only change occurs when I switch the thermostat dial from hot to cold - when I do it gets hot on hot and on cool it returns to outside air temp.



    however - one of my tubes is hot - the other warm - it should be cool since it is the evaporator side.



    here is something new - my psi pressure on the system ranges from green to blue - it was green to slightly blue before I topped off with coolant - btw, I was carefull not to go past blue on the pressue gauge. The evaporator side was slightly cooler but not cold before I topped off the coolant. Are these pressure swings common? Interestingly, after I filled to blue - took it for a test drive (unsuccessfully) and then rechecked the pressue it had shot up to red.



    Could this be a bad leak? If so - are the leak sealers found in the store any good?



    What is your opinion:

    Do these store bought coolant refills work well? or - can I release the pressue through the stem or should I take it to a shop and have it vacummed dry and refilled with coolant?



    Is there another possible cause that should be investigated? The air did not stop suddenly - over a day of heavy driving the cool air began to fade - it completely faded the next day driving around town.



    Any help or questions you can offer are appreciated.



    Kevin

  • KPILMAN Jul 25, 2008

    Thanks again - there seems to be a fair swing between the high and the low pressure so I assume the compressor is ok (since it is also running and the clutch is engaged). Do you agree?



    what did you mean by "the sys should always be pulled down to a steady vacumm for 5 or 10 minutes to check for leaks and to remove any moisture that is present" - these off the shelf coolant refil products don't include this step in thier instructions. Is this something a dealer should do or are these vacumm tools available to the DIYer at a reasonable cost?

  • KPILMAN Jul 25, 2008

    Yeah, it was low - in the green (15psi - 35psi) but not completely empty. what was unusual was the variation. I took these measurments with the car and AC on - compressor and clutch spinning.



    It is now at 45 a bit in the yellow on my gauge.



    The evaporator is not cold at all, but the compressor seems to run and coolant and pressure are in the system.



    Weird.



  • KPILMAN Jul 25, 2008

    emwiz - if you prefer - my cell # is 404-229-5115 Kevin

  • rmel Aug 26, 2008

    kpilman,

    I'm also having the exact same problem.  The AC doesn't get cold, but the gauge is in the blue.  The compressor doesn't stay on even on the coldest setting, it keeps cycling on and off.  I topped off the freon, the gauge was at the top of the blue and shot down to top of green when the clutch was out.  Did you ever solve this one?
    RM

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  • GMC Master
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Is 1 of the 2 AC (under the hood) lines cold? if so you may have a blend door problem, that door is in the dash air duct distribution system, it mixes are between the hot heater core and the cold AC evaporater core to give the set or desired air outlet temp, When you turn the defrost on does it blow hot/cold as the lever is moved back and forth? The compressor turning off and on is normal cycling of the system, when it reaches a preset pressure in the low side line, a pressure switch will open and compressor will "cycle off" when the press starts to rise to a preset limit the compressor will "cycle on" and so on. I assume you have an electric bled door, older cars and trucks use a cable operated mechanical door.

Posted on Jul 25, 2008

  • yadayada
    yadayada Jul 25, 2008

    The evap side should be cold, very cold, you need to verify the sys is full and then check hi/low pressure, if there is little difference between hi and low side the compressor may be the culprit. The R134 you buy is the same that the dealers use, the sys should always be pulled down to a steady vacumm for 5 or 10 minutes to check for leaks and to remove any moisture that is present.

  • yadayada
    yadayada Jul 25, 2008

    Pulled down means the R134 sucked out until ther is a vacumm of at least 30 inches, is the low side line very cold? that is to say near to having frost on it? You could have a blend door issue as well in the AC air distribution. I don't recommend any type of AC sealers they are a watse of money, was your system charge low to start out with before you did anything to the system?

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