Another APU question

Discussion in 'Trucking Electronics, Gadgets and Software Forum' started by WREN, Oct 7, 2019.

  1. WREN

    WREN Medium Load Member

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    Jul 17, 2017
    Florida panhandle
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    Yesterday I was cleaning the truck and packing it. The APU was running and cooling the truck but I didnt have any sleeper power. It does have the inverter and the 2 110 plugs, but none of the sleeper lights or anything like that was working. Does the APU only power the 110 plugs and the ac/heater? If so, do I need to just leave my key in the on position to have power to the rest of the truck?

    Never had an apu so its all new and the videos/literature really doesnt explain this very well.
     
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  3. mitrucker

    mitrucker Road Train Member

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    Lapeer, MI
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    If you were just issued the truck, I would suggest asking the shop about it. If that’s not an option, drive it. Get a good full charge on the batteries, then recheck.
     
  4. WREN

    WREN Medium Load Member

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    Jul 17, 2017
    Florida panhandle
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    Its my personal truck that I just purchased a couple of days ago. Im not use to all this fancy new stuff or an APU so its all throwing me off lol. The batteries showed 13.3 volts since the APU does charge them.
     
  5. supersnackbar

    supersnackbar Road Train Member

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    My Mack was tripping the low volt breaker under the bunk every time I started it last week. It shut down most of the sleeper lights and all of the 12v outlets, but my APU would start, run and charge the batteries. There is probably a fuse or a bad relay. They replaced the breaker and mine hasn't had an issue since. If it's a normal APU like a Thermo King tripac or Carrier, it shouldn't be connected to anything but the inverter and the batteries, and a wire to the ignition so it knows to shut down when you start your truck.
     
    WREN Thanks this.
  6. underdogg25

    underdogg25 Bobtail Member

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    Jul 23, 2015
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    I've been running my own truck with an APU now for the last 8 years. Done all the repairs myself when the warranty ran out. The APU is a completely separate unit from the tractor, except for the truck engines coolant, also fuel from the trucks fuel tanks which runs through both the APU and to Truck engine. Without the coolant and fuel from from the truck engine it will shut down the APU within a few minutes. The APU should charge the truck batteries, provide power to the Inverter, also has it's own ac unit completely separate from the trucks ac. Also if a bunk heater was installed with the APU it is also separate from the trucks heater. When the batteries on the truck get too loe to start. Just fire up the APU & presto the batteries with charge right up. Yeah! Saved me countless numbers of times. It's a beautiful thing.
     
  7. WREN

    WREN Medium Load Member

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    Jul 17, 2017
    Florida panhandle
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    @underdogg25 so how do I get the interior lights to have power if I'm running just the apu? Turn the ignition key to on?
     
  8. WREN

    WREN Medium Load Member

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    Jul 17, 2017
    Florida panhandle
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    Nevermind, got it figured out. Gfi was tripped
     
  9. jland1962

    jland1962 Bobtail Member

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    Aug 15, 2018
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    Hi. I don't have a reply to your comment other than to say, Good job! But you seem knowledgeable, so I'm asking for advice. I have a Thermo King Tripac APU. The inverter stopped working, off & on. The APU quits, on occasion. I jiggled the wires under the APU, and it started back, but for 3 hours or so. Not sure if it is bad wiring, bad inverter, APU issue...

    Suggestions?? TIA
     
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