Is there more then one place to replace AC refrigerant, 379 with sleeper

Discussion in 'Peterbilt Forum' started by Mr. Cob, Jun 7, 2022.

  1. Mr. Cob

    Mr. Cob Light Load Member

    Howdy All,

    I have had my Pete, for four years, in that time the AC has slowly started to lose cooling capacity, gradually blew warmer air. No visible leaks, I found a BLUE capped AC fitting used to add refrigerant on the upper left hand side of the outside firewall, I looked but couldn't find another port, I don't know if the cab and the sleeper share the same unit or if the sleeper has a separate fitting that needs to be filled.

    I followed the instructions on the do it yourself kit, started engine, turned the AC on full, fan on high position, and filled until the gauge read 50. Stopped filling, the AC seems to be blowing a bit cooler but it is not cold. Truth is with the engine running I can't hear if the AC compressor is running or not, looking at the tach if I turn the AC off, then on, I can't see any difference in RPM so I honestly don't know if the compressor is working.

    So if anyone has knowledge of another fill port or a way for an IDIOT to check to see if the compressor is running I sure would appreciate your advice. Oh this is on a C15 single turbo Cat if that makes any difference. Thanks.

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  3. baha

    baha Road Train Member

    Jul 25, 2013
    You need to look at the center of the ac compressor to see if it's turning then its on if not spinning then its off when you get it nearly full of freon it will start to cut off and on and the fan will start turning turning on and off when its nearly full of freon so you know it's about full of freon.
  4. Coolbreezin

    Coolbreezin Light Load Member

    Jun 11, 2016
    I have a '91 379, 3406b. I was told that there is a completely separate a/c unit under the bed in the sleeper. I can access mine from the passenger side door. I havent bothered to test or use it as Im a local driver. Check the lines in the side box and under the sleeper in the immediate area.
  5. flood

    flood Road Train Member

    Dec 25, 2010
    your truck has 2 ac units but it's all ONE system..
    1 compressor runs all if it...
    Coolbreezin and AModelCat Thank this.
  6. AModelCat

    AModelCat Road Train Member

    Jul 7, 2015
    Should be 2 ports. Low pressure and high pressure.

    Never worked on a truck with a sleeper before but have always been told its just one system but with an extra evap core and blower in the sleeper.
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