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(Topic ID: 205546)

O/t furnace question

By amkoepfer

2 years ago

Topic Stats

  • 17 posts
  • 6 Pinsiders participating
  • Latest reply 2 years ago by Dayhuff
  • No one calls this topic a favorite


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    #1 2 years ago

    I have a carrier 58mca060 furnace at a rental house that is driving me nuts. The blower motor doesnt have the juice to get it spinning (once it starts its fine) i took the run capacitor in, it tested bad, he gave me a new one. Worked for a day, then it stopped working again. The motor will whine until it locks out. I can see the blower turning very slowly, but it wont go without a push. Stupid me, i didnt look at the original for the specs. The new one is 5mf 370/440v. I dont have a manual to see if that is correct. Would it hurt to put a 7.2mf cap in? Could it be something else? Any help would be appreciated since i really dont want to call someone out! (Guy tested my motor and said the motor is fine) could dirty fan blades cause this? I didnt have my meter to see if the new cap id bad or just not powerful enough. Thanks!

    #2 2 years ago

    Motor bearings seizing up? If about 20 years old and used for both heat & Air Conditioning, it is likely time to replace the blower motor. Mine did the exact same thing to me this summer (22 years old) capacitor worked for a day or two, then stopped. New motor worked ever since.
    Repair (Canton, MI) has bunches of them in stock if you want to make the short drive up today.

    #3 2 years ago

    I had the motor checked out by a motor repair guy by me, he said it seemed great, just a bad cap. If i have to replace the motor thats fine, but id hate to drop a couple hundred when its just an underrated 7 dollar capacitor. After work ill test the cap to see if its good or bad. But youre right, it wouldnt hurt to replace the motor

    #4 2 years ago

    Check for play in the bearings on the shaft end of things. Shaft will move a little left and right, but should not move up or down. This would indicate bad bearings and in turn a bad motor. Putting a larger capacitor on would still probably not provide the extra needed torque to get the motor started. Save your self the headache and replace the motor and cap.
    Hope this helps.

    #5 2 years ago

    Ok, thanks. Ill probably just do that. Will that cause a limit switch lockout if it cant start up after so long? My tenant says there was the code for that, but i didnt see that code

    #6 2 years ago

    Of course everyone closes at 5 when i work till 530!

    #7 2 years ago is open until 7pm for counter service.
    Order online by 6pm and it will be waiting for you. But, if you don't preorder and get there at 6:55 and there are people in front of you, they will wait on you no matter how long it takes.
    Best to preorder to verify they have yours in stock. They also have universal models.
    800-269-2609 if you want to call in an order.

    #8 2 years ago

    Cool, thanks a lot!

    #9 2 years ago
    Quoted from amkoepfer:

    Ok, thanks. Ill probably just do that. Will that cause a limit switch lockout if it cant start up after so long? My tenant says there was the code for that, but i didnt see that code

    There may be a small hose attached to the shroud surrounding the "squirrel cage" of the fan assembly. That hose would connect to a sealed bladder assembly that gets pulled by the suction created by the spinning squirrel cage. There is a micro switch on this bladder that signals if there is a suction created by the spinning fan/blower. If it doesn't spin, there is no vacuum and the switch does not activate so the furnace shuts down and a fault code is generated.

    #10 2 years ago

    No hose, i had it out the other day, but it could be higher up, and could be pressure instead of vacuum. I will look tonight and report back

    #11 2 years ago

    The presure switches are usually for proving the vent motor is running .The limit is likely high temp limit related to motor problems .Pull the blower and clean the blower wheel ,instlall new motor and capacitor .If new motor is a reversable motor make sure it's rotating the proper direction

    #12 2 years ago

    If you had the motor out, the cap needed for it is on the nameplate of the motor. Often obscured by the belly band mount.

    #13 2 years ago

    Thanks for all the replies. I figured the limit switch would have to do with no air flow. Ive seen what happens to heat exchangers with no flow. I figure if im replacing the motor and cap, ill probably replace the wheel as well. Id rather start fresh with everything. Ill probably replace the condensate trap as well since that isnt looking the best

    #14 2 years ago

    Well i called several places without having the motor info handy, and no one could tell me a for sure motor. I went over there and found the numbers i need, tore the motor and fan apart, cleaned the fan and housing, checked the cap and put it back together. It fired right up and sounded great! I was able to get the numbers so i can search for a new motor, but at least they have heat. The motor does say 5mf capacitor, but also says some models need 7.5mf would there be an issue with me just putting the 7.5 mf in there just to help? Hopefully it stays working and thank you everyone for all your help!!!!

    #15 2 years ago

    I doubt cleaning it would have repaired it. Did you test the capacitor with a capacitor tester or just check for continuity?

    Did it stay working?

    Also, I have not seen a Carrier or Bryant furnace call for 2 different capacitors on the same motor.
    The next size up from the 5 is a 6 MFD. The 7.5 is more common than the 6.
    It is acceptable, though I do not recommend it, to go up to 10% higher in MFD. The 7.5 does not fall into that bracket.
    It will work but the motor is destined to fail.

    #16 2 years ago

    It was weird, but said right on it 5mfd, some may call for 7.5. Anyways, i cleaned the cage, worked for a couple days, then went out. Replaced motor and capacitor and now it works, i just forgot to update results. The old motor i could feel it catching when i spun the shaft, so i figure it was bad

    #17 2 years ago

    Yup I figured it was the motor from your original post but didn't see this thread until just now and read all the way to the end of it. Glad you got it figured out or at least lets keep our fingers crossed.


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