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  1. #1

    Hmm Goodman heat pump - blower motor run capacitor failed twice, what's wrong?

    Something has - I think - destroyed the motor run capacitor on my heat pump, but I am not sure what it is.

    Back story:

    I have a Goodman 3.5 ton heat pump, model ARUF036-00A-1A. Two nights ago I woke up to the smell of something electric burning, and the sound of the blower motor stalled while trying to start.

    The motor run capacitor is a 7.5uf and 370v, part number 27L566. I picked up a replacement capacitor, which is the same except it is rated 440v/370v at the recommendation of the local HVAC shop. This is a Mars #12931. I installed that, turned the HVAC power on, and it worked fine.

    At that time I noticed a transformer (see below, left side) in the air handler was buzzing, and I don't recall it making any noise before. I looked at it, and the fuse that is installed was not blown, so I buttoned things up.

    Last night I again woke up to the smell of something electric burning and a stalled blower motor. I turned the power off to the heat pump.

    I took photos of the heat pump innards, CLICK to get full-sized image:

    Transformer on the LEFT is buzzing:



    Motor run capacitor:



    Can someone tell me if this is a simple fix - is the transformer? Computer board? Or do I need to call someone?

    Thanks!

  2. #2
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    2,716
    you need to call someone.
    ignore the buzzing, it's normal from the transformer.
    capacitors fail. and sometimes they are bad out of the box, but I'd have someone out to actually check out the system and find the fault.
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
    Mel Gibson
    Dwane Johnson
    The A/C repairman

  3. #3
    Join Date
    Dec 2012
    Location
    Rancho Cucamonga, CA
    Posts
    22
    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

    Further infractions may result in loss of posting privileges.
    Last edited by beenthere; 12-14-2012 at 04:38 PM. Reason: Non Pro * Member

  4. #4
    Quote Originally Posted by Justhowe View Post
    I agree
    Thanks guys, I appreciate the advice.

  5. #5
    Thought you'd appreciate an update - the technician diagnosed the blower motor had failed. It has ... uh ... one of the windings grounded out. Basically, it is shorting out. In addition, it spins very poorly. I've ordered a new one and will have it installed.

    He also discovered that it was the wrong sized motor. The motor is one size too small, which he says can cause premature wear because it's working too hard, and additionally it causes poor airflow. Poor airflow has been a big issue since we moved in, so hopefully the correctly sized motor will fix that, as well as better heat/cool my house.

  6. #6
    Join Date
    Aug 2012
    Posts
    2,329
    Quote Originally Posted by Jessie james View Post
    Something has - I think - destroyed the motor run capacitor on my heat pump, but I am not sure what it is.

    Back story:

    I have a Goodman 3.5 ton heat pump, model ARUF036-00A-1A. Two nights ago I woke up to the smell of something electric burning, and the sound of the blower motor stalled while trying to start.

    The motor run capacitor is a 7.5uf and 370v, part number 27L566. I picked up a replacement capacitor, which is the same except it is rated 440v/370v at the recommendation of the local HVAC shop. This is a Mars #12931. I installed that, turned the HVAC power on, and it worked fine.

    At that time I noticed a transformer (see below, left side) in the air handler was buzzing, and I don't recall it making any noise before. I looked at it, and the fuse that is installed was not blown, so I buttoned things up.

    Last night I again woke up to the smell of something electric burning and a stalled blower motor. I turned the power off to the heat pump.

    I took photos of the heat pump innards, CLICK to get full-sized image:

    Transformer on the LEFT is buzzing:



    Motor run capacitor:



    Can someone tell me if this is a simple fix - is the transformer? Computer board? Or do I need to call someone?

    Thanks!
    Quote Originally Posted by Jessie james View Post
    Thought you'd appreciate an update - the technician diagnosed the blower motor had failed. It has ... uh ... one of the windings grounded out. Basically, it is shorting out. In addition, it spins very poorly. I've ordered a new one and will have it installed.

    He also discovered that it was the wrong sized motor. The motor is one size too small, which he says can cause premature wear because it's working too hard, and additionally it causes poor airflow. Poor airflow has been a big issue since we moved in, so hopefully the correctly sized motor will fix that, as well as better heat/cool my house.
    Why would the motor be sized wrong? I am sure you did not order the OEM replacement for the unit. Remember when trying to save money you will usually end up spending more.
    I think we let this one get to out of hand.
    Trying not to be a Hack.

  7. #7
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,278
    Jesse J,

    Having a blower motor fail after run capacitor replacement is actually a regular occurrence. I always tell customers after I change a bad run cap on a blower that there is 50/50 chance of the blower dying within the next few weeks.

    My theory on this is below, I have no proof to back it up so take from it what you will.

    Blower run caps get weak over time. I believe that the prolonged restarting under a reduced valued capacitor causes the bearing/windings to fail prematurely.

    Condenser fan motors don't have the same issue because blower run caps are exposed to significantly less inrush current than a dual cap on a condensing unit. The dual cap fails when weakened enough that the inrush current blows the capacitor before the bearings/windings receive any damage.

    Hope that makes sense. And if this is completely inaccurate; someone feel free to correct me.

  8. #8
    Join Date
    Nov 2009
    Location
    Kansas City
    Posts
    124
    They are not like batteries that get weak and you have to change them. A capacitor should stay the same forever. Remember the old capacitors that they used to put in units that had PCB in them, you can check the microfarads in them and they still have what they did 30 yrs ago. The parts made nowadays are just cheap crap from china. These capacitors I replace sometime only last 1 summer.mthey don't make things like they used to

  9. #9
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,322
    Ditto on Jblack's post. Call a pro, and bite the bullet. Did ANYONE check the RPMs on old motor?? I'm assuming you got new motor over internet? They have a special "warranty" on them motors I'm sure........

  10. #10
    Quote Originally Posted by wahoo View Post
    Ditto on Jblack's post. Call a pro, and bite the bullet. Did ANYONE check the RPMs on old motor?? I'm assuming you got new motor over internet? They have a special "warranty" on them motors I'm sure........
    JD, Wahoo, you are both offering sound advice. I'm just a little put out. I do have the tech scheduled to come out and look at it. They were nice, I can't imagine they'd be rude.

    The last motor was clearly toast, it would barely spin. Yes, I ordered the new motor online here:

    Links to direct purchase sites are not permitted here.

    I just can't see how I screwed up the install. It's trivial. Unscrew the set screw from the blower fan that attached to the motor shaft. Unbolt three bolts from the old motor. Slide old motor out. Swap metal bushings from old motor mount holes to new motor mount bushings. Slide motor in. Install bolts. Be sure set screw is on flat edge of motor shaft. Install set screw on blower fan to motor shaft. Slide housing into air handler and bolt it in. Wire using existing wires which match identically. Test.

    The motor ran fine for a day, at least 10 hours of use. Suddenly on the start up yesterday afternoon it sounds like someone dropped a rock in the motor.

    Yeah, in the end I probably ruined it somehow. That's okay. At least I gave it a try. I'd rather break something and learn a lesson than not. So I'm going to be broke for a month, nothing new. That's life!
    Last edited by beenthere; 12-21-2012 at 01:14 PM. Reason: Link to direct purhcase site

  11. #11
    Update: I removed the set screw from the cage/shaft, repositioned the cage slightly, tightened it back up and now the noise is gone.

    Question: There is still a small amount of vibration present. Is this normal?

  12. #12
    Quote Originally Posted by n7943h View Post
    jessie,
    The burned wire was caused by a bad connection which caused resistance locally and high heat which melted the fitting and ends of the wire and not related to your motor issues. The new wire and good fitting connection should be the end of that problem. That loose connection did not cause increased currant flow (amps) so the breaker would not protect the wire in that case.
    Thanks for the explanation.

    Quote Originally Posted by n7943h View Post
    Can you get a view of the blower squirrel cage and watch it while it is running to see if it running true in the blower housing and not wobbling?
    Ok, I did this. It is very hard to tell if it's not centered or is loose. I grabbed the cage and tried to move it every which way and it seems as solid and as tight as can be.

    Quote Originally Posted by n7943h View Post
    Watch it when it is spooling down so you can see better. If the blower ran fine without noise the first day than something has changed since then. I would start by checking the attachment of the squirrel cage again and make sure that is not loose on the shaft and hitting the sides of the blower housing or just flexing on the shaft.
    It's not hitting the sides, it's about 3/4" away on each side. I was careful to be sure it was centered in the housing for that very reason.

    Quote Originally Posted by n7943h View Post
    I have seen the actual squirrel gage break. With the power off give everything a tug and shove. If everything looks and feels normal and it still makes that noise and vibration you can remove the assembly and dismantle it and run just the motor by itself and see if the problem goes away. Make sure that the motor shaft runs perfectly true because anything but perfect will make the cage wobble and produce vibrations at speed. I would bet it runs fine and smooth and the issue is with the cage and its mounting. Make sure nothing is inside the cage and causing it be unbalanced ( are you missing a glove?)
    I may do that. No lost gloves! Haha.

    Quote Originally Posted by n7943h View Post
    Good on ya for learning about you equipment and learning how to maintain it and I wish you a merry Christmas and a warm house.
    Thanks very much!

    Well, now get this. After I yanked and tugged and etc., the noise is gone! Somewhere a screw or a bolt is loose, and it's probably in the 6' 4" tall, 180 pound homeowner ...

    So, I'm an idiot (like someone's signature on this thread mentions) and installed it wrong somehow. I am going to let the techs come fix it proper.

  13. #13
    That's interesting, thanks for the info.

    Now, onto new questions I forgot to ask.

    While the HVAC serviceman was here he noticed that one of the wires to one of the emergency heat strips was burned up, and you can actually sort of see it in the photo I took - it's burned all the way OFF of the connector and bubbled the wire coating:



    This clearly was the burning smell I noticed. So ...

    1. Does that mean my heat pump has been using the heat strips (emergency heat) during daily use?

    2. Shouldn't that wire be fused?

    I'm AMAZED and frightened that the wire burned up before something tripped, this just seems stupid dangerous to me! Yes, I know it's a big current draw, but I've used 30-50-100 amp fuses/breakers on car stereo applications, why wouldn't there be one here?

    I am also not thrilled that the emergency heat has been in use, because that just means a bigger bill for me. I'd rather use my portable oil-filled radiators if needed...

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