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A/C pressure ?

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  • A/C pressure ?

    2004 Silverado 2500HD 6.6 Duramax. When engine idles the low pressure gains under 1500 rpm the low pressure goes back down. The A/C works fine unless at an idle the temperature slowly climbs as well does the low side prssure. Is the compressor going out or could there be another cause ? The low side is at 40, and gaining at an idle have seen it almost peg the canister gauge in the red ! Any Help please

    Yes I did buy a can of AC Pro. I am in Alaska at present time I have gauges and a evacuator pump in WA state. I did not put any 134a into system for when I hooked the can up the gauge showed high yellow side. So I drove on later do not recall how long or how long I let the truck idle, when it has been close to 90 here when I hooked the can back up it was in the red. SO Early this morning it was only 70 ambient temp. The gauge showed 40. When I let it idle it kept climbing, When I went to 1500 rpm the gauge would drop back to 40. From every thing I have read or information I could find the compressor is going out. Yes it is not high dollar gauges but it is still a gauge. If it is climbing when at idle and drops back under higher rpm is this a bad sign of compressor failure? What else can I check ? every thing seems to work fine except at an idle after about 15 minutes it quits putting out cold air, eventually it quits working electric clutch is engaged just no cool air ??
    Last edited by Buddy; 07-25-2018, 09:57 PM.

  • #2
    I'm guessing you have one of those "kits" that has a single gauge on the can? The people in the industry call those "death kits" because you are more likely to do more harm than good.
    If you didn't start from completely empty and put the factory amount in by weight, chances are very good that you have overcharged the system. A/C work is not do it yourself friendly and has got much less so since the switch to orifice tube systems.
    The gauges on those cans are notorious for being inaccurate and your only reading the low side, so you have no way to know what is happening in the system.
    My best advice is to have the system pulled down to a vacuum and start from scratch. Hopefully you know someone with the right equipment to tackle the job correctly.
    I know this is not what you want to hear, and I am not a shop owner, I am a trucker and truck repair guy that only does my own vehicles. I have invested a lot of money in A/C tooling to do the job right. I am telling you this so you will know that I have nothing to gain by what I pass on, I do not make my money off A/C work.
    A/C work can get real expensive real quick if you do it wrong or miss something.


    • #3
      Just yesterday bought on of those gauge on can things at least states 100% 134a nothing more and common BS what it should read on color gauge not worried about. I want the product if side tapped and the hose and coupler was brass not plastic. Just a test and can use the product with things run that thru real gauges known accurate forget the rest then bust it up see what the hidden end of apparently good hose is and how connected.

      Basically it's just more costly if that's accurate info now pure product inside vs right beside it ones had sealers and oils you don't want at all - ever. Do that AYOR or last ditch and give up is your biz just be "buyer aware" of what you are really getting as much as anything can be trusted. Uggh - trusting those gauges is NOT known unless compared to a real known IMO AND experience. Wrong info is worse than no info for this trade of its own,
      MetroWest, Boston