379 A/C blowing cool, sometimes briefly cold

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Coolbreezin, Jun 3, 2020.

  1. Coolbreezin

    Coolbreezin Light Load Member

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    Jun 11, 2016
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    Hey all. My 1991 379s a/c lost its chill. I checked the freon and it was at 35, so I added a little. The a/c clutch spins like normal. My mechanic tested the system with the valves and explained to me that it wasnt balancing like it should. He said theres a blockage. He wants to replace all expansion valves, dryer, pag oil, and flush the system. Its not that I dont trust him or his word, but that seems like overkill. I found online that the txv valve could be the culprit. So I was thinking of starting there. Any advice or ideas please. Thank you.
     
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  3. boneebone

    boneebone Road Train Member

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    The expansion valve usually gets clogged up and gets stuck, it's a relatively inexpensive part to purchase $40-50, the receiver/drier should be replaced anytime you open up the system, it's about $22.

    Doing a service on your system should bring it back to the level it was previously.
     
    Coolbreezin Thanks this.
  4. Deere hunter

    Deere hunter Heavy Load Member

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    What he said^^^^^^^^^ if it’s blowing cool but not cold and a little muggy it’s definitely the expansion valve in the sleeper. Your mechanics just trying to fix it right the first time!
     
  5. truckdriver31

    truckdriver31 Road Train Member

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    bigguns Thanks this.
  6. truckdriver31

    truckdriver31 Road Train Member

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    dont not flush with the ac compressor lines connected. also flushing the condenser really doesn't work either. unhook lines and flush lines and evap with a ac citrus flush. replace dryer/expansion, maybe condenser
     
  7. jcarter

    jcarter Bobtail Member

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    Jan 21, 2018
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    On a 379 pete it could be the core inside the truck needs cleaning .
     
  8. Coolbreezin

    Coolbreezin Light Load Member

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    Jun 11, 2016
    Florida
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    Im contemplating running a 5000 btu window a/c unit in my cab off of my batteries. I have 4 950cca diesel batteries going to a 3500 watt inverter. All about 1.5 years old and still quite strong. I cant find any info regarding how many batteries/power I should have going to the inverter. When I did this before, the inverter would state it was too low on voltage and would turn itself off. So I was wondering if I added two batteries and tied them all together would be of any benefit. Any advice is appreciated.
     
  9. Deere hunter

    Deere hunter Heavy Load Member

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