A/C blows warm in my '99 'Burban

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by hihoslva, Jul 20, 2008.

  1. hihoslva

    hihoslva New Member

    Hello all. I'm new to the forum - as well as a new-to-me Suburban owner.

    I've got a '99 5.7L (350) engine, 4wd, 143,000 miles.

    It's got the dual-zone climate control and all that jazz, but neither the front nor rear is working all that well. The A/C simply doesn't blow cold. More like barely cool. I'd call it warm.

    The rear *may* be a little cooler than the front, but neither is chilly by any stretch of the imagination.

    Starting with the basics, I checked the system pressure (with a gauge from an R134 recharge kit) and it read dead-on at 45, which is - according to my limited research - right where it should be.

    And now I'm about out of ideas, being that I don't know all that much about these systems.

    Looking for advice before heading to a mechanic. I'm a hands-on guy who will try to fix anything any way I can before paying someone else to do it, so teach me something!

    It's hot here in Arizona, and A/C is not an option - it's a necessity!

    Thanks for any/all ideas!
  2. sysmex

    sysmex New Member

    Is the clucth engaging in the compressor when you turn it on?
  3. Applegeek

    Applegeek New Member

    Yes, make sure the clutch is engaging - ie. the center part of the pulley on the AC compressor is turning when the AC switch is on. Also make sure the coils on the front of the radiator or free of debris. Make sure the heater / ac system isn't full of leaves, and make sure the heat-control door isn't stuck open allowing warm air in (If you have it on "vent" at night is the air still cool?). Also check the fuses for the AC system, sometimes there are two.

    Now the other thing is take that gauge on the can of R134a and throw it out - these can be very misleading. It is quite possible that your system still needs freon, but if you check it when its hot out, it will always read high. If you look at the can, the guage only tells you something over a very narrow temperature range. Try looking at it again when its cooler. DON'T press the button on the top of the can when reading the temperature, as this will make it read high also.

    If that doesn't help just go to a decent shop and have them check the refrigerant levels with a good set of gauges. A complete AC diagnostic and tune-up should be less than $100.
  4. hihoslva

    hihoslva New Member

    Not to leave a thread hanging - an update on my situation:

    It was a leaking discharge hose. Knowing I was not going to able to fix/diagnose the problem myself, I took the truck to a local auto AC shop that was highly recommended by a friend.

    They diagnosed the problem in all of 45 seconds, and fixed it within an hour. The entire hose assembly was replaced, I paid them $300, and now my air is blowing' cold!

    They gave me some info about R134 systems that might be of interest to others here:

    According to the mechanics, R134 systems - for reasons that cannot be completely explained - will take in air when they have a refrigerant leak. In fact, they will take in air and maintain a proper system pressure! So novices like me cannot diagnose the problem as a leak, because our simple gauges and tools show a correct system pressure.

    Often, people will just dump a can of 134 in, and then the system can very quickly over-pressurize and detonate the compressor and other parts.

    My system was running on about 1/4 the proper amount of refrigerant, yet a low-side pressure gauge showed normal.

    So word to the wise: Don't just dump a can into the system. If you have an issue you can't resolve, don't guess. Find a reputable shop and let them fix it, or at least diagnose it for you. Guessing wrong can cost you a LOT more money. $300 for a new hose assembly and system recharge versus $1200-$1800 for a whole new system......you do the math.

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