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Hot furnace blower motor

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garykrzn
garykrzn Member Posts: 6
Motor gets hot when not running then cools while running

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  • garykrzn
    garykrzn Member Posts: 6
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    New motor on it's way! Motor gets hot when not running then cools while running. Any help as to why?
  • Jamie Hall
    Jamie Hall Member Posts: 23,441
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    Does it get hot when it's not running but with current still going to it? Could be a problem in the windings. However, if the power is off to the motor and it still gets hot... the heat is coming from something else -- and quite possibly when it runs its own cooling system cools it off.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Alan Welch
    Alan Welch Member Posts: 270
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    Possibly a crack or hole in the heat exchanger.
  • HVACNUT
    HVACNUT Member Posts: 5,864
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    Bad run cap?
    Did you order one with the motor?
  • SuperTech
    SuperTech Member Posts: 2,186
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    You aren't providing enough information for anyone to be able to help you. Make,model age of the unit? Pictures?
  • garykrzn
    garykrzn Member Posts: 6
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    It's an Intertherm furnace. Early 90's. Capacitor free motor. Can hear a slight buzz (electrical) when motor is not running! Motor heats up when off. Motor is new today. I'm guessing 3 way on/off/fan switch may be bad.?? Not sure what else could cause this issue. Furnace and motor operation is fine otherwise. Heat exchange is also fine. Nothing gets hot, just motor when not running
  • SuperTech
    SuperTech Member Posts: 2,186
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    No capacitor on an early 90's furnace? That doesn't seem right. Anything that old should have a capacitor. I should be able to help you if you can post a picture of the wiring diagram and the blower on the furnace. Sounds like something isn't wired right.

    How many wires go from the motor to the circuit board?
  • HVACNUT
    HVACNUT Member Posts: 5,864
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    Belt drive?
    Open neutral?
    Mice with Zippo's?
    A little help.
    Post the wiring diagram please.
  • garykrzn
    garykrzn Member Posts: 6
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    The furnace model # mgha-075abfc-01, when I ordered new motor I asked for capacitor also. Was told motor didn't require one! I searched blower housing and there is no capacitor. Also there is no control panel. All there is from Tstat is a transformer, limit switch, fan switch and 3 way on/off/fan switch. Only other wiring goes to switch on gas valve
  • garykrzn
    garykrzn Member Posts: 6
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    3 wires from motor, 1 to the limit switch, 1 to transformer, and 1 to fan 3 way on/off/fan switch
  • garykrzn
    garykrzn Member Posts: 6
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    Furnace worked fine for years until a week ago. Motor started squealing and seized.(enclosed bearing oil free motor) New motor identical match. When I installed new motor is when i heard buzz and noticed new motor getting hot (150-160 deg) before cycle starts.
  • ratio
    ratio Member Posts: 3,652
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    Pics of the schematic from the door too please.
  • Jamie Hall
    Jamie Hall Member Posts: 23,441
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    Got to have the schematic. You may have enough voltage going to that motor to heat the windings when its "off", but not to run it. That would give you the buzz.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England