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A/C blows hot- but everything else seems normal


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  • A/C blows hot- but everything else seems normal


    I have a 2001 Suburban 1500 4WD with the 5.3 L engine and the towing package.

    My air conditioner started blowing hot air. The air out the front vents is 82 degrees F and the air out the rear vents is 65 degrees F. The engine is not overheating, the compressor is engaged and seems to be working, the low pressure pipe is cool and damp, and the high pressure pipe is hot but not so hot you can't hold your hand on it for a few seconds.

    The only unusual thing is a hissing noise near the collector when the a/c is running and for about ten seconds after the engine is turned off. It has always hissed so I have always assumed this is normal.

    I checked the pressure on the low side- with 90 degree F ambient temperature the pressure is about 50 PSI which is normal according to the test kit I have.

    It started blowing warm on Friday. 95 degree temp outside, I was driving at freeway speeds and towing a light boat. Engine temp was just under 210 on the gauge which is what it usually is when warmed up. The problem got worse Saturday and is now holding at 82/65 degrees front/rear.

    Does anyone know what is going on here?

    Thanks for the help.

  • #2
    Re: A/C blows hot- but everything else seems normal

    try checking the little plug on the passanger side below the dsash


    • #3
      SOLVED- Re: A/C blows hot- but everything else seems normal

      I think I fixed it. I was troubleshooting tonight and noticed that at 2000 RPM the pressure dropped below 30 PSI and the compressor turned off. I started adding refrigerant and kept testing the pressure at 2000 RPM until it stayed above 30 psi. After two cans the problem seems to be solved.

      With an ambient temp of 90 F the duct temp dropped 40 degrees. Remembering the days when I hung out at my friend's dad's auto shop (23 odd years ago), I believe a 40 degree drop is the standard reference point for a/c performance. Now I just need to figure out where and how bad the leak is.

      I hope this helps someone else, because no A/C in August really sucks.


      • #4
        Re: SOLVED- Re: A/C blows hot- but everything else seems normal

        I am having the same problem. I just inherited my wifes 2001 suburban (she got the new -well 92k new 2007 Denali) anyway it was running hot at low speeds and I thinjk I have a couple of problesm the belend door actuator. I removed it and manually put the door in a/c. and a freon leak, I charged it up yesteday and was getting some 40' reading last night but thought the low side pressurew was too high @ 48psi so today I removed some freon and the temps went up @ 80 in the front and 68-74 in the rear, Put some freon back in and temps got better still around 50 in the front and 46 48 degrees in the rear at about 35 - 40 psi low side.

        What is the low side pressure supposed to be on this Suburban - all the other vehicles I have had did best arounnd 26-30 psi on the low side with 134A

        Any ideas???

        thanks Matt