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Carrier APU question on install

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Skiharleydoo, Oct 8, 2022.

  1. Oct 8, 2022 #1
    Skiharleydoo

    Skiharleydoo Bobtail Member

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    When hooking up the apu to the coolant system, is there a in-flow and out-flow ? In other words is it a one way flow only ? I had to move my apu and when I disconnected the water hoses I didn’t mark them.
     
    Skiharleydoo, Oct 8, 2022
    Skiharleydoo, Oct 8, 2022
    #1
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  3. Oct 9, 2022 #2
    ibcalm19

    ibcalm19 Road Train Member

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    Yes it would be, when you have a coolant system the pump pulls coolant in & pumps it out. You want to make sure you have the hoses installed properly.
     
    ibcalm19, Oct 9, 2022
    ibcalm19, Oct 9, 2022
    #2
  4. Oct 9, 2022 #3
    Skiharleydoo

    Skiharleydoo Bobtail Member

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    That kinda makes sense, however plumbing the coolant supply is coming off the trucks engine block via heater hose, therefore 2 taps from the engine block, why would it matter? The water pump on the apu, assuming it has one, would draw on the suction side and circulate the coolant back to the trucks engine block. I don’t see where it would matter. Guess I should speak with a carrier installer. Thank you anyhow.
     
    Skiharleydoo, Oct 9, 2022
    Skiharleydoo, Oct 9, 2022
    #3
  5. Oct 9, 2022 #4
    Freightliner22

    Freightliner22 Bobtail Member

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    Apr 22, 2022
    Athens tn
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    I installed mine tk apu myself and think connected to coolant system wrongly, it wasn't heating my coolant much. Then asked wallmart driver with same truck/ apu to pop his hood and took bunch of pictures where the two hoses connect. Switched the hoses now it works perfect
     
    Freightliner22, Oct 9, 2022
    Freightliner22, Oct 9, 2022
    #4
    Oxbow and MartinFromBC Thank this.
  7. Apr 6, 2025 #5
    Skiharleydoo

    Skiharleydoo Bobtail Member

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    The correct way is to get a flow meter (Amazon) to determine the flow direction of the heater hoses and the APU.
     
    Skiharleydoo, Apr 6, 2025
    Skiharleydoo, Apr 6, 2025
    #5
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