1988 Peterbilt ac issue

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Vgarza32, Sep 8, 2023.

  1. Vgarza32

    Vgarza32 Bobtail Member

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    Feb 27, 2018
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    I have a 1988 379 Peterbilt. Truck does have a bunk ac. I just replaces both expansion valves, the condenser, the dryer, and compressor. I flushes the system while apart and fired it up. Truck cools very well at night but has a very difficult time cooling during the day. It’s over a 100 degrees down here and I can’t get this truck to get under high 70’s out of the vent during the day. Has me really scratching my head. Thanks in advance
     
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  3. BoxCarKidd

    BoxCarKidd Road Train Member

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    Did you vacuum the system down before charging? Are your CAC cooler and radiator cores really clean to allow the most air flow. Do you have cut off valves on your heater hoses at the engine and are they closed? How do you know the amount of freon you put in the system is correct?
     
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  4. blairandgretchen

    blairandgretchen Road Train Member

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    Times 2 - and replace air filter and cores real good. They sell some spray on hose off that works ok.
     
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  5. AModelCat

    AModelCat Road Train Member

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    What refrigerant does the system call for and what type did you put in?
     
  6. wore out

    wore out Numbered Classic

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    CHASIN THE DEVIL'S HERD
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    Your capillary tubes in your evaporator cores clog with crud over time….there is some size difference from R-12 original to 134a retrofit. Mine used to be swampy and terrible replaced every piece including air box inside. 40 degrees all day long baby not bad for a 91
     
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