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Thread: induction motor not working.

  1. #1
    DIY Junior Member beastmaster's Avatar
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    Default induction motor not working.

    The induction motor on our older air/heater unit isn't working so nothing else heat related is either. It was working fine up tell it wasn't. I pulled the motor/fan unit(fasco p/n 1054268). It wasn't getting hot, and it spins freely by hand.
    I check the lead coming from the relay and there is no power coming out of it. I had the thermostat turned up in the house. I am assuming it should of had the relay turn power on to the relay, and then to the motor. Is that right? Does this point to the relay as the problem? Or could it be some thing else not causing power to the relay?
    Where does one buy a replacement relay at? I can't afford a tech to come out, and its freezing. I got 4 small electric heaters running and its still cold in here, please help me help my self. Thanks

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    The coil of the relay will have (probably) 24vac on it if it should be energized. ALso, the input to the relay should have line voltage on it (it could be either 120vac or 240vac, depending on the type of motor). On many furnaces, there's an internal thermostat that looks at the heat exchanger temp, and turns the fan on when that gets hot. So, it could be an internal fan control thermostat. Does the burner come on, then go off? If it comes on, how long does it run before it shuts off?

    There are so many things that could be preventing it from running that without more info, it's impossible to say. If you have the manual(s) that came with the thing, read the theory of operation, then follow the sequence of operations...see where it stops. Then, follow the control voltage. When the thermostat is turned on and off, do you hear a relay in the furnace energizing (it might not have a mechanical one, it could be electronic)? the thermostat on your wall may no longer be working, and it may not be sending the signal to the furnace. That's fairly easy to check IF you know what you're doing. All the thermostat is is a switch. WHen it calls for heat, it closes an internal switch that applies 24vac to the furnace to energize it into heating operation.

    A HVAC supply store would likely have a compatible relay and they usually aren't all that hard to replace, but it's a waste of time and money until you verify it's actually being told to energize - the relay could easily be fine, and there's some other system fault. Modern furnaces have lots of safety interlocks, and it could just as easily be a safety switch that is no longer working, or it has actually detected a fault, and is preventing the furnace from running.

    So, more info is needed.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Plumber jimbo's Avatar
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    Inside the unit somewhere should be a wiring diagram. That will help you figure out where power is getting lost.

  4. #4
    DIY Junior Member beastmaster's Avatar
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    The induction blower nor the gas or burner comes on. There is 210 coming out of both legs of the motor, yet its not running. I disconneted the second leg from the relay and it still has voltage. Its running through the motor from leg one. Is this normal?
    I tested the pressure switch. Its good. I took the relay apart and cleaned it up, but its not doing nothen. I tryed jumping some of the contacts to see if the motor would start, no go. I can jump the burner and it'll turn on. I tryed jumping it at the control panal X Y R G C and only the big blower will start.Name:  024.jpg
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Size:  59.5 KB Any more advice?

  5. #5
    DIY Junior Member Failure2Comply's Avatar
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    If you are trying to describe your "Combustion Fan Motor/Inducer Motor" then if the motor has the voltage listed on the motor nameplate feeding it (230v) and it does not run, verify the voltage from the wires to the motor. Unless you are a business you should have 230v, not 210v feeding the motor. Is the motor hot? Shut off all electricity to the unit and pull the wires to the motor and ohm the motor windings. Report back.

  6. #6
    Plumber jimbo's Avatar
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    Reading 220ish from each leg of the motor to ground ( or neutral ) indicates that no current is flowing through the motor. One side of the line is getting there, and there is an open circuit in the other side which should complete the path. Things that can be open are the system relay, and possibly the limit switch and rollout switch.

    If you connect a meter ACROSS the motor ( one meter lead on each wire) a reading of 220 indicates motor has voltage applied and if not turning it is bad. If the reading is zero, then you have an open circuit as I mentioned.

  7. #7
    Jack of all trades DonL's Avatar
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    You may want to check the 24volt from the outside unit.

    Does your outside unit have power ?

    It looks like the 24V transformer that controls the blower is powered by the outside unit.
    Theory only works perfect in a vacuum.

    Cyber Security Protection for Windows C:\ > WWW.WinForce.Net

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    DIY Junior Member Failure2Comply's Avatar
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    Please post a name brand, model number and serial number of this unit.

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