Comfort Pro Apu Issues (solved)

Discussion in 'Trucks [ Eighteen Wheelers ]' started by mitchtazz, Apr 12, 2014.

  1. mitchtazz

    mitchtazz Road Train Member

    Sep 6, 2009
    Lake Wales, Fl
    I bought a used Milton truck back in Sept.. Up until recently i've only did routine maintenance which is fairly cheap seeing as how it's only every other month.. In all honesty I spent more money on the APU that's on the truck then the truck itself, until the end of March I put it in the shop for a PM, and to have an oil leak check. Which ended up costing $6k.

    But anyway, a back in January the APU stopped putting out 120vac. It would start and run just fine (after i bled the air out of the fuel line) but it wasn't putting out any current which meant all I could do was keep the engine warm and recharge my batteries. So every month when i'm home on hometime, i'll spend a couple of hours tinkering with it.

    The first thing i found was that Kenworth MHC neglected to put a shut off valve on my coolant lines, which was an issue when i was replacing the water pump..
    After that i had the oil pressure sending unit act all crazy for two days and kept making the engine shut off.
    And then recently I couldn't even get it to start because it kept saying "Main Engine Interlock".

    So after finding copies of the service and owners manual i dug deep. Found that there's a relay that control the engine interlock.. mine had seized up. Jump'd it over to test, and the APU started just fine. I was even able to buy the fuse in the Pilot for $10.

    For the no voltage issue, the manual says if there's no voltage before the 35amp breaker, then the capacitor is the suspect, but the only way to test is with a good capacitor.. Kept digging through the manual and found that there's three capacitors in the actual HVAC unit under the bunk. Got down to it and pulled the large one out.. Wired it in and fired it up and got my little lighting bolt back..

    I shut everything down pretty quick because i wasn't sure if it was the right size or what not. So now i have to wait until Monday to get two capacitors from the TransCarrier dealer in Florence, Sc so i can get my APU back up and running..

    In all honesty if it turned out that the generator was shot, i was just going to buy another belt driven compressor and a 300amp alternator and rig in there and call it a day.

    I know when i was searching google for answers as to why my Control Panel would say the main engine was on when it wasn't, i saw some other people that were having the same issue.. hopefully they make it here and read this. Labor rates are crazy!!!
    Last edited: Apr 12, 2014
    Hitman89, D.Tibbitt, KB3MMX and 2 others Thank this.
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  3. Madtrucker3

    Madtrucker3 Bobtail Member

    Feb 10, 2014
    My apu keep getting air in lines and doesn't run just cranks last time the guy at carrier pumped it some how idk but I'm not Tryin to go back and spend crazy also my heat n AC does work he said it's not giving off enough volts and that I need a new generator $1600... So one told me to check capacitor
  4. WitchingHour

    WitchingHour Road Train Member

    Apr 1, 2011
    Broomfield, CO
    Air in the fuel lines, or in the coolant lines?
  5. Catrucker47

    Catrucker47 Bobtail Member

    Nov 2, 2016
    We had kind of the same issue with the 110 not producing enough voltage , we talked to the shop and had to remove a link in the belt. The issue that we have now is the unit will start up as we are driving down the road. I have looked all over for a way to stop it from doing it but so far, nothing .
    KB3MMX Thanks this.
  6. WheresWaldo

    WheresWaldo Light Load Member

    Nov 23, 2016
    Turn off your comfort settings. Also why it might also be starting is if you have battery monitor on but not calibrated.
    Hitman89 and KB3MMX Thank this.
  7. Elroythekid

    Elroythekid Road Train Member

    Sep 9, 2010
    Halifax Nova Scotia
    Had one 2 trucks ago. It stopped making ac. Took the generator off, it was $2k to replace from the dealer. Took it to an electric motor shop. He took it apart found it had cheap Chinese bearings that had failed and the windings had briefly shorted and blew diodes that are soldered on the end of the windings. He stripped the coating checked the windings, which were good, replaced diodes, replace bearings with better bearings, worked like a charm for $250.
  8. bzinger

    bzinger Road Train Member

    Dec 10, 2014
    omaha , ne
    Thanks for that post .
    I got a buddy with the same problem that carrier wants insane money to fix ...I'll let him know .
    KB3MMX and Elroythekid Thank this.
  9. Strangeland

    Strangeland Bobtail Member

    Apr 7, 2017
    jason6541 Thanks this.
  10. Strangeland

    Strangeland Bobtail Member

    Apr 7, 2017
    Put a fuel primer for a boat motor on the fuel line. I self installed my APU. Works like a charm...
    Last edited: Apr 7, 2017
    Reason for edit: Put a fuel primer for a boat motor on the line
    KB3MMX Thanks this.
  11. Strangeland

    Strangeland Bobtail Member

    Apr 7, 2017
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