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isaac509's avatar
isaac509
Explorer
Jul 22, 2015

A/C fan quit

I recently bought a 2010 Itasca 24V class C motorhome, which is equipped with a Coleman-Mach roof A/C unit.

I was on park power the other day, had run the A/C in the last half hour but I just had low-fan running at the time. The fan suddenly quit, and would not restart. I don't hear any humming or reaction at all when I move the dial around.

The breaker never tripped, and I've got voltage at the L1 terminal inside the A/C switch panel. However, it's reading lower voltage than my A/C supply.

I'm measuring 97v AC at L1 with everything turned off, and at the same time I'm seeing 125v at the other 110 household jacks in the R/V. I don't know if this is significant or not.

I removed power and did continuity checks on the switch - its doing what the diagram says it should be doing in various fan and cool modes.

I have not found any cut and dried troubleshooting info yet, and I apologize if this question has previously been covered on the board. I did search around before posting, I promise! :)

Ant clues, or things to check next? I tried calling the local shop in my hometown that does A/C, and their phone has been busy nonstop for two days. This is going to have to be DIY repair, I must try at least!

Any help appreciated,

- Eli

10 Replies

  • j-d's avatar
    j-d
    Explorer II
    Jul 23, 2015
    Good! Go over your breaker panel and make sure every connection is tight. They loosen a little at a house, and RV gets all that vibration.
    Welcome! You'll be helping us before long!
  • isaac509's avatar
    isaac509
    Explorer
    Jul 22, 2015
    The system is running. At this point, I've had everything apart, poked at every connector.

    I can only assume that the AC supply breaker was loose in it's slot, and that pulling and reseating it was the actual fix. That was the last thing I did, I had been reapplying power and testing from time to time, and I decided to chase back and see if the low voltage reading I got at L1 yesterday was legit or not.

    This is the first time I've posted here, but I've gotten a lot of good info with other problems just reading, and some great advice in this thread. Thank you folks for your help, I'll be keeping my fingers crossed that this isn't an intermittent issue.

    Thanks!

    - Eli
  • j-d's avatar
    j-d
    Explorer II
    Jul 22, 2015
    If you've got a meter, turn power OFF. Then short across each capacitor in case one or more is holding a charge. Then take them out-of-circuit by disconnecting at least one of each cap's two wires. At that point, you should be able to measure the uF/MFD of each and compare with each one's labeling. I know that'll work for Fan Run and Compressor Run. The Plastic one is a Compressor Start "Device." By Device I mean a Capacitor plus a couple other components. One of those may be a resistor that keeps you from testing without breaking its connection. If only the FAN is not running, then disconnect and measure only that capacitor. Probably about 7.5 MFD at 370 or 440 Volts AC. Bear in mind that your fan motor has a thermal cutoff inside and may need time to cool before it'll run again after getting hot. Hot as in from having power applied and not being able to start.
    I have a Coleman fan motor with bad bearings but good windings, if you're into taking things apart instead of replacing. I couldn't get the bearings to keep working, so I replaced it, about $100 on Amazon. Some new motors come with a new cap, but Amazon's does not.
  • isaac509's avatar
    isaac509
    Explorer
    Jul 22, 2015
    Answering my own post here ;)

    There are three caps that I found. A large metal one, a small metal one, and a midsized bakelite one.

    I tested all three using this procedure: http://www.wikihow.com/Check-a-Start-Capacitor

    .. and everything checks out from a resistance standpoint.

    My meter measures capacitance, but the numbers I'm getting don't make any sense on any one of the three caps I found. I think I'm doing something wrong there.

    - Eli
  • isaac509's avatar
    isaac509
    Explorer
    Jul 22, 2015
    I can spin easily the fan by hand, and I _think_ I heard a small noise from the fan motor when I switched the fan on.

    Is there a test procedure for the capacitor, or do you diagnose by replacement? I tried calling the local RV A/C guy again and just got voice mail :)

    Thank you for the advice, I really appreciate it.

    - Eli
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Jul 22, 2015
    This is why I LOVE
    INFATUATED
    ENCHANTED

    With an accurate panel volt/amp meter in my rigs. Switch off all other AC loads and see exactly to the dot how many amperes a device is consuming.

    Same for the DC meters and DC loads.

    A diagnostic tool unparalleled in usefulness.
  • Chris_Bryant's avatar
    Chris_Bryant
    Explorer II
    Jul 22, 2015
    That's good for any PSC style fan motor. You can also spin it backwards, and it will run- another good sign.
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Jul 22, 2015
    Doug may I ask a question?

    When my Coleman cap went bad I could hand spin the fan and get the fan started and then it ran fine and checked out with correct amperage draw. Would this type of diagnostic be valid on other types of A/C units? Thanks.
  • dougrainer's avatar
    dougrainer
    Nomad
    Jul 22, 2015
    1. Can you turn the fan by hand and it freely turns?
    2. FIRST thing is to check the Fan start capacitor. This is a common problem on RVP Roof AC units-----Bad Fan Capacitor. Doug

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