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APU inside A/C fan not blowing

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Gears, Jun 19, 2011.

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  1. Jun 19, 2011 #1
    Gears

    Gears Trucker Forum STAFF - Gone, But Not Forgotten.

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    Boy, if it's not one thing, it's another.
    Here's the prob:

    Comfortmaster APU. It has a full charge (134A), new dryer, new expansion valve and new o-rings. The compressor turns on when the A/C is turned on. So far so good. Only problem, is the fan that blows the cold air, she's a no go. Looking for suggestions from you wizards as to how you would troubleshoot that system.

    You guys have helped me out on more than one occasion and I appreciate it...thanks again in advance for any suggestions you may have regarding this.:biggrin_25514::biggrin_25514::biggrin_25514:
     
    Gears, Jun 19, 2011
    Gears, Jun 19, 2011
    #1
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  3. Jun 19, 2011 #2
    Les2

    Les2 Road Train Member

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    Check and see if it has power to the fan first. If not then find out if it has a resistor of some sort on it. Usually if its the resistor going bad the fan will work on one setting but not the other, but not always. It could also be the switch. If all else fails find which one is the hot wire and run a jumper to it to make sure the fan isn't bad.
     
    Les2, Jun 19, 2011
    Les2, Jun 19, 2011
    #2
    Gears Thanks this.
  4. Jun 19, 2011 #3
    rollin coal

    rollin coal Road Train Member

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    I agree with Les check for a bad resistor. I had a bad resistor causing the blower fan to stop blowing after a few seconds on medium or high. This was on the truck cab AC. New resistor was 12 bucks. I also had a bad AC thermost making the system freeze up and that cost 30 bucks. Hope it helps good luck.
     
    rollin coal, Jun 19, 2011
    rollin coal, Jun 19, 2011
    #3
    Gears Thanks this.
  5. Jun 19, 2011 #4
    rollin coal

    rollin coal Road Train Member

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    Also, if the resistor is bad when you turn that fan on if you're near the fuse box you'll hear the breaker cutting out. It'll be hot too. Put a new breaker in while you're at it.
     
    rollin coal, Jun 19, 2011
    rollin coal, Jun 19, 2011
    #4
    Gears Thanks this.
  7. Jun 20, 2011 #5
    Gears

    Gears Trucker Forum STAFF - Gone, But Not Forgotten.

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    Thanks for the help guys. You all ROCK!
    Here's 'nuther dumb question... this resistor you speak of, where abouts would a guy look for it? I'm about to head outside and tear into things... wish me luck!
     
    Gears, Jun 20, 2011
    Gears, Jun 20, 2011
    #5
  8. Jun 20, 2011 #6
    oneshot

    oneshot Medium Load Member

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    The resistor is usually located inside the a/c box so the a/c can keep it cool.Wires run from the resistor to the fan.It is close to the fan.Good luck.
     
    oneshot, Jun 20, 2011
    oneshot, Jun 20, 2011
    #6
    Gears Thanks this.
  9. Jun 20, 2011 #7
    Gears

    Gears Trucker Forum STAFF - Gone, But Not Forgotten.

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    Gottcha. I think I may have it figured out, but want to be sure before posting my findings (in case anyone's interested).
     
    Gears, Jun 20, 2011
    Gears, Jun 20, 2011
    #7
  10. Jun 20, 2011 #8
    Hardlyevr

    Hardlyevr Road Train Member

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    sometimes the resistor is bypassed when the fan switch is in the high speed position, so if this works you know it is the problem.
     
    Hardlyevr, Jun 20, 2011
    Hardlyevr, Jun 20, 2011
    #8
  11. Jun 20, 2011 #9
    Rerun8963

    Rerun8963 Road Train Member

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    gears, hear are some samples of what a blower motor resistor can look like.


    http://www.autozone.com/autozone/pa...4D883C1A2C1D83FFAA19FCE72583D0C.diyprod1-b2c1

    now, some are located in the a/c box under the dash, some are located on the inside of the firewall, some can be OUTSIDE under the hood in the heater core box...

    there will be wires of course, and you could by pass the resistor if you only have one wire in, one wire out, other wise i would NOT recommend by passing anything with more wires coming from it...

    heck, you may even be able to buy a new resistor at an auto parts store...just bring the old one with you.
     
    Rerun8963, Jun 20, 2011
    Rerun8963, Jun 20, 2011
    #9
  12. Jun 20, 2011 #10
    Gears

    Gears Trucker Forum STAFF - Gone, But Not Forgotten.

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    OK, I think my problem is a combination of two. I took a test light and checked for power to the box, there was none. Went to the APU where the wires from the box go to the APU via a snap connector. I pulled the connector apart and discovered the red wire was not contacting it's mate on the box side of the connector. There was power. Fixed the connection and the fan fired, but the wire got hot and the fan ran only at one speed and then cut out. I believe the resistor is at fault in this instance from what I've read in this thread. If I'm correct the resistor has two spade connectors coming from it and there's two blue wires connected to it. I should have snapped a picture of it.

    So my next question is.... Do you think replacing the resistor will solve the fan speed and hot wire issue?

    Thanks and my friends...
     
    Gears, Jun 20, 2011
    Gears, Jun 20, 2011
    #10
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