Lennox AC Compressor Problems -- Capacitor?

Discussion in 'HVAC' started by SomewhatHandy, Jul 19, 2008.

Help Support House Repair Talk by donating:

  1. Jul 19, 2008 #1

    SomewhatHandy

    SomewhatHandy

    SomewhatHandy

    New Member

    Joined:
    Jul 19, 2008
    Messages:
    3
    Likes Received:
    0
    Hi all;
    I've been lurking in the shadows for a while and have come out with some good advice over the years. So, to start off... Thanks for all the past help!

    I've got a Lennox 10acc-036-230-02 compressor (condenser?) that just started not working yesterday evening. After shutting of power, waiting a while, then restoring power, it continues to not work. Neither the fan nor the compressor are running, but both are humming and get very hot (and the capacitor seems to be warm, as well). If I give the fan a push, it'll run, but not as fast as it used to. The fan bearings don't seem to be an issue, as it turns freely. I have no way to evaluate the state of the compressor (that I know of).

    From what I've picked up here (and other sites), my best guess is a bad starting capacitor. This unit uses a dual start 50 / 7.5 MFD 330 VAC, though Cozy Parts suggests that Lennox is now replacing them with a 50 / 7.5 MFD 440 VAC (which I've ordered). I should have no problem replacing the part once I get it -- it looks easily accessible. And yes, I understand the appropriate electrical safety concerns -- especially having been zapped a few times by capacitors I was sure could no longer hold a charge. :^o

    Now, the questions:

    1) Am I on track here, or are there other things to consider?

    2) Is there a way to evaluate the compressor?

    3) Most importantly, after several hours trying to track down a capacitor locally (northern VA), I could find nobody to sell me a part. If they had parts, they only sold to contractors, or they wanted to send a tech out for a service charge of 80 to $300, plus $80 for a capacitor (which I bought for $20 from Cozy). Is it always this hard to find parts locally, or am I not calling the right folks? Where have y'all obtained parts in the past?

    Thanks, again!
     
  2. Jul 19, 2008 #2

    glennjanie

    glennjanie

    glennjanie

    Well-Known Member

    Joined:
    Mar 1, 2006
    Messages:
    2,990
    Likes Received:
    6
    Welcome SomeWhatHandy:
    Yes, you have a good start on the trouble shooting. You may test a capicitor with an ohmmeter (preferably with an audible tone). Just disconnect the wires and touch the ohmmeter to the two leads; your audible ohmmeter will go to a high pitched whine and quickly taper off. Remember there is a capicitor on the compressor and another on the fan; its good to test both of them.
    To evaluate the compressor; unplug the three wires to it and use the ohmmeter again (this time you need a digital readout which you will record in all three positions) put one lead against the compressor body making good contact, touch the other lead to each of the three contacts and record the reading. Your readings should be such that any two added together will equal the other. If that doesn't happen the compressor is dead.
    While you are digging out all these wires to disconnect you will probably run into one on the compressor that is burned off and not making contact at all. Cut the burned portion of the wire off, crimp a new female plug to the end of it and plug it to the compressor. Clean all three contacts with a wire brush or 100girt sandpaper.
    You might also check at the contactor for burned off wires.
    The wholesalers will not sell to walk-ins because they are protecting their full time mechanics who want to keep a closed organization. Find a United Refrigeration wholesaler and sound like you know what you are doing, it may or may not work.
    Let us know how you turn out with this. We may be able to help more as you experience more or take pictures of your work.
    Glenn
     
  3. Jul 21, 2008 #3

    kok328

    kok328

    kok328

    Well-Known Member

    Joined:
    Nov 20, 2007
    Messages:
    2,845
    Likes Received:
    274
    The particular capacitor that you have, has 3 poles on it. It must be reinstall exactly how you removed it. One pole is the common one of the other two goes for the fan and the other one goes to the compressor. You don't have separate capacitors for the fan and compressor.
    See if you have a Grainger's near you, they should have one in stock and will sell to walk in's.
    Before you go resplicing connections and stuff, you'll have to start at the beginning w/some basic troubleshooting.
    Is the compressor contactor engaged?
    Are you getting proper voltage to the compressor?
    Are you getting proper voltage to the fan motor?
    If yes then the component is bad.
    Is the thermostat calling for cool?
    Are there any fuses, main feeds or on a circuit board, that are bad?
    Is the high pressure switch tripped?
    Is the low pressure switch tripped?
    Is this a 3phase system or a single phase system?

    Answer these questions and we should be able to provide an accurate diagnosis.
     
  4. Jul 21, 2008 #4

    SomewhatHandy

    SomewhatHandy

    SomewhatHandy

    New Member

    Joined:
    Jul 19, 2008
    Messages:
    3
    Likes Received:
    0
    All;

    Many thanks for the good tips. Here's the latest.

    I've looked over all connections, none were questionable, but I cleaned connectors, re-seated the clips, and tightened screws. There are no circuit boards, just one relay (which appears to be clean and working -- it at least provided power to the motors).

    I'm hesitant to check voltages (I can deal with 120, but get a bit nervous around 220), so I haven't done that yet. However, as both the compressor and fan motors were quite warm (too hot to touch), I'm starting off by assuming they both had power going to them. Oh, and it's single phase.

    I performed Glenn's suggested check on the dual-use capacitor. I don't have an audible ohmmeter, but even on the 2000 M ohm setting, I barely registered any measurable resistance (effectively infinite, though it did flicker some numbers occasionally). I don't know if it's significant, but I can hear a fluid sloshing inside the can -- I'm guessing it's the oil.

    The resistance readings on the compressor were OK, too.

    So, as of now, I'm sticking with the capacitor as the primary culprit. Hopefully, it'll arrive from Cozy tomorrow. I'll update when I get it in.

    Again, many thanks for the hints and tips. Hopefully, I'll get some pix of some of the more successful projects posted in the gallery (especially my deck and finished basement/bar).
     
  5. Jul 22, 2008 #5

    kok328

    kok328

    kok328

    Well-Known Member

    Joined:
    Nov 20, 2007
    Messages:
    2,845
    Likes Received:
    274
    Leave the unit off until your new capacitor arrives.
    If the new capacitor doesn't do the trick, then you'll have to check voltage to the unit.
    It sounds like you've lost a leg of power.
     
  6. Jul 23, 2008 #6

    SomewhatHandy

    SomewhatHandy

    SomewhatHandy

    New Member

    Joined:
    Jul 19, 2008
    Messages:
    3
    Likes Received:
    0
    All;

    Got the new capacitor from Cozy. Installed in a few minutes, and I now have a functioning AC.

    Further examination of the old capacitor seems to indicate that at least one of the lugs are not connected electrically.

    Thanks to all for the tips and suggestions. I'm glad I was able to get it done myself and save several hundred dollars.

    Cheers!
     
  7. Jul 24, 2008 #7

    kok328

    kok328

    kok328

    Well-Known Member

    Joined:
    Nov 20, 2007
    Messages:
    2,845
    Likes Received:
    274
    Cool ! (sorry about he pun ... lol)

    I forgot to mention that aside from the bad terminal, a capacitor is likely to swell, when it goes bad.
     
  8. Aug 9, 2011 #8

    clow

    clow

    clow

    New Member

    Joined:
    Aug 9, 2011
    Messages:
    1
    Likes Received:
    0
    Hi i have a similar cenerio with a linnox 2 ton ,furnice functionig ok but nothing from the condencor. The contacter is close for call ,the cap is new and working ,red and green on board are flashing in synnc,,still condcor not running. Help
     
  9. Jan 19, 2013 #9

    randyortan

    randyortan

    randyortan

    Junior Member

    Joined:
    Jan 19, 2013
    Messages:
    1
    Likes Received:
    0
    wow! this is a great post. I am sure a lot if MSI users will be interested in this.
     
  10. Dec 6, 2014 #10

    emccracken

    emccracken

    emccracken

    New Member

    Joined:
    Dec 6, 2014
    Messages:
    1
    Likes Received:
    0
    got a Lennox Heat Pump 12HPB30 unit, contactor chattering, having difficulty pulling in consitantly.
    Any help in troubleshooting issue?
     
  11. Dec 7, 2014 #11

    kok328

    kok328

    kok328

    Well-Known Member

    Joined:
    Nov 20, 2007
    Messages:
    2,845
    Likes Received:
    274
    Check for steady voltage on the contactor coil and if it I s good then replace the contactor. Around $25. 24vac/30 amp 2-pole. About 30 minutes of work. Larger more expensive contactors can be repaired if contacts are still good but these small vac contactors are disposable.
     

Share This Page