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Problem: Furnace Blower motor works intermittently?

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Problem: I have the following problem, but only intermittently.  It usually happens about every tenth time or so that the furnace goes off, but it has been happening less frequently lately. Not sure why.
I have a Carrier 58DH. The call for heat goes, the gas ignites, the unit heats up, but then the blower doesn’t engage.  After a while, the safety switch kicks in and turns off the unit which is overheated.   There is also a burn smell in the house.  I wait for the unit to cool down, trip the reset button on the top of the blower, turn the furnace back on, and it generally operates well for a number of cycles.
Any idea what might be wrong?  I had the control panel changed out on this unit about five years ago.  I know it is an older unit (1984), but I can’t afford a new one at the moment.
Thanks, Ron

AnswerThe burn smell could either be caused by the heat exchanger getting real hot and burning the old dust off the heat exchanger or the blower motor could be getting too hot and causing an burning electrical smell. I would suggest that the next time the blower does not come on to turn the power off to the furnace, take the furnace door off and lightly feel (touch) the blower motor to see if it is hot or not. If the blower motor is hot I would see if you can spin the squirrel cage (blower wheel) freely. You should be able to spin the blower wheel and the wheel should continue to turn for a few seconds after you spin it. If the wheel does not turn freely then you probably need a new blower motor because the motor bearings might be dragging the motor down and causing it to over-heat. If the wheel turns freely, I will suggest having the motor run capacitor checked. Some appliance parts places will check capacitors out for free. We sell capacitors on the following page: Please click here if you are interested in seeing the capacitors we sell. If the capacitor checks out OK then you might have a control board problem. The fan relay on the control board could be acting up periodically and causing the fan to not turn on. If you want me to recommend a control board I will need your furnace’s product number. I hope you get the problem figured out. I also hope that you have a great day! Please email us anytime if you have a question. Our email address is: arnoldservice@gmail.com We would love to help you out and earn your business!

Steve Arnold, https://arnoldservice.com

14 thoughts on “Problem: Furnace Blower motor works intermittently?

  1. I am having the same problem as the original post. Blower runs well then very so often it does not run and it overheats and the burning smell throughout. The blower spins freely. It appears my motor ones not have a capacitor. Bryant 925as series. So does going after the board seem like the next logical place?

    1. Hi Mark! Most of the time when there is a smell in your home it is coming from the blower motor overheating. If it is not the blower motor capacitor causing the problem then more than likely you will need a new blower motor. I would like to suggest that the next time the blower motor starts working intermittently that you turn off the power to your furnace and lightly touch the blower motor to see if it is hot to touch. If the motor is hot to touch then this is a sure sign that the motor is going bad. Our Bryant parts program did not find any furnaces that start with 925as. I will need the product number in order to look up parts. If your blower motor does not have a capacitor then it is either probably a really old shaded pole motor or a really new ECM motor. I would need your furnace’s product number in order to look up parts. I would also suggest that you test the two wires that come out of your control board and go to your blower motor (usually one white neutral wire and one wire that is connected to “Heat” on the control board) and see if the control board is sending 110 to 125 volts AC to the blower motor. If the control board is sending the 120 volts to the motor when the motor is supposed to be running then you know the control board is good and not a fault. If you are not getting the 120 volts to the motor then you could have a bad control board. If you would like for me to try and look up the blower motor and control board for your furnace then please send me your product number to arnoldservice@gmail.com. I will be glad to try and help you out. Thanks for asking this question. When you find and fix the problem please let me know. Thanks! Steve

  2. My central heat and air system. Using the same blower motor works fine on ac but when turned to heat it runs first cycle ok then won’t come back on. Or will come back on for a few seconds then off repeatedly could this still be the run capacitor or is it the board.

    1. Hi Douglas! More than likely the problem is in the control board because the control board on most furnaces times the length of time the gas burners are on before the control board allows the blower motor to come on. I always look for simple, inexpensive solutions first and I would suggest that you test the capacitor to make sure it is in good condition. The blower motor runs at a slower speed in heating than air conditioning so a weak capacitor could cause the motor to not run or run erratically in heating mode. If the capacitor tests out OK then I would suggest that you test the two blower motor wires that are used to start the motor during the call for heat (usually white & red or white & blue wires). If the motor is not getting 110 volts to start the motor then I would think you have a control board problem. If you are getting 110 to 125 volts to the blower motor and the motor is not starting then I would think you have a blower motor problem and will need a new motor. Please let me know if you would like for me to look up parts. Please send me your furnace’s name brand and model number to our email address: arnoldservice@gmail.com. I hope you can easily find and fix the problem. Steve

  3. My furnace motor will run for a while (3 to 5 minutes) then slow down and stop.
    Got any ideas?

    1. Hi! I would like to suggest that you check your blower motor’s run capacitor to make sure it is up to specifications. If the capacitor is in good condition then more than likely you will need a new motor to fix your problem. I would suggest that you check and see if the motor is running hot. If the capacitor is good and if the motor is running hot then more than likely the motor bearing is going out and you will need a new motor. Steve

  4. I just replaced the capacitor in my furnace, the blower motor worked for 10 or 15 minutes, then it stopped again. I have been having a problem for the past eight days. My first clue to the problem was that I smelled something that smelled like it was burning. I turned off the thermostat, and upon examination, it turned out that there was a hickory nut in the blower motor. I thought that the hickory nut was preventing it from turning, but within half an hour of getting the hickory nut out, the furnace started making a bad noise and the smell was back. I don’t know if the noise had happened the first time, because I was wearing headphones when I first smelled it. Since then, the furnace has worked for no more than half an hour at a time before the fan stops, and I often think the fan is too slow. However, the squirrel cage spins just fine. It isn’t overheating as far as I can tell from feeling it. I guess it could be the bearings, or maybe it just got damaged because of the resistance from that hickory nut.

    My furnace is really old. It was installed in 1980. It is an electric furnace without a heat pump. I don’t think it even has a control board. From what I have seen elsewhere online, my next step should be checking to see if the control board is bad, but I just replaced the sequencer earlier this year, and I never saw anything that looked remotely like a circuit board. I don’t know if it even has a fan relay per se. I don’t know what I should do next. I don’t want to replace the entire blower motor if I don’t have to, especially if that won’t even solve the problem. Any advice would be very much appreciated. It’s going to be 6° F tonight and it’s already down to 56 degrees in my house.

    1. Hi Susannah! Since you replaced the capacitor and it did not help the problem that you are having with the blower motor stopping then the only way to tell if the blower motor is bad or not would be to test with a voltmeter. you could either have an electrical problem that is causing the blower motor to stop or a blower motor that is going out. You would need to test with a voltmeter set to “Volts AC” the two power wires that go into the blower motor. Since you have an electric furnace most blower motors are 220-volt motors. If you are getting 220 to 245 volts to the blower motor and it is going off then I would say that you need a new blower motor. If you are not getting the right voltage to the motor then you have a blower motor control problem. Many times on the old furnaces they use sequencers to turn the fan motor off and on. We have a pretty good post with Youtube videos on how to troubleshoot electric furnaces on the following page: https://arnoldservice.com/problem-electric-heat-will-not-come-on-or-fan-will-not-come-on/ I hope this helps you out. Steve

  5. Hi Steve,
    Somehow, I thought I would be informed by email that you had been kind enough to answer. But I was not, and I did not check back until now. That also explains why we have not heard from Ron. Anyhow, thanks for your thoughts!
    Like you, I think it is nice to help out other people that might have the same problem. I think I have an understanding to share here.
    My fifth failure occurred after 47 days. At day 51, I put in a new capacitor. (By the way, the original capacitor measured good at low voltage, as I said. It also shows no bulging, which would have been a symptom of impending failure.) At day 53, I was looking around trying to figure out how to trigger an oscilloscope with the failure when I noticed that one of the motor wires was not fully seated in its connector.
    It has now been 24 days since I put in the new capacitor and 18 days since I put plugged the motor wire in completely. My statistical analysis tells me that it is 90.5% probable that the problem was either the capacitor or the connector. I have put the original capacitor back in place today. On March 1, if I have not had another failure, I will be able to say with 99.25% confidence that the connector was the problem. If it is the capacitor, I would expect five failures by March 1. I hope to remember to update you and anyone else who finds this webpage.

    1. Thanks so very much for sending us the update! God bless you! I hope you have a great and Happy New Year! Steve

    2. It is March 1. I promised to report on March 1. I have had no additional failures. This makes it almost certain that my intermittent blower motor problem was the incompletely seated connector to the blower motor. Whew.

      1. Hi Joe! Glad to hear that you found and fixed the problem with your blower motor! Thanks for letting us know what the problem was and that it is fixed. Thanks! Steve

  6. I am having a similar problem, about every ten days. I only caught it doing the burn-smell thing once, all other failures were not noticed until the house cooled down. Anyhow, I wonder what Ron finally found his problem to be.
    In my case, the problem first occurred during a planned power shutoff. I initially blamed it on disconnecting the furnace, thus turning off the blower, when the gas was burning. Other interesting hypotheses include off-frequency operation of my generator/inverter, and a poor waveform. But it still happened four more times in the last month. (One more interesting observation: One of the prongs of the power cable was badly blackened. I cleaned it up.)
    I replaced the controller board due to a debugging mistake, so that is unlikely to be the cause since it happened with both the old and new controller board. I tested the blower motor (though not when hot) and it spins freely; when the problem happens, the blower is presumably not hot when it won’t start, so the motor seems an unlikely cause of the problem. I replaced the capacitor this week, but the old capacitor tests good using low-voltage electronic equipment; I suppose it could still misbehave intermittently at full voltage and thus not get the motor started.
    In addition to those three possible problems listed by Steve (controller, motor and capacitor), there is also the wiring, including that between the controller board and the blower motor. The Carrier furnace is 32 years old but in good condition.
    I also replaced the high temperature limit switch, though it appears to be doing its job well.

    1. Hi Joe! I do not believe that you will be able to find the problem until the problem is actually happening. I hope that maybe Ron will see your problem and respond. I would recommend that you tape your blower door safety switch down so you will not be losing power when you do some testing when the problem occurs. When your blower motor will not start I would suggest testing with a voltmeter to see if the control board is sending 120 volts out to the blower motor. Of course, if the control board is not sending 120 volts to the blower motor then you have a control board problem. If the control board is sending 120 volts to the motor and the motor is not running then you have a motor problem. Maybe you have a bad place on the motor rotor or windings that when it lands in that position the motor will not start. Just guessing! I do not like hearing that you have a blacken power cable since this means as you know arcing, heat and high amp draw. You said that you smelled a burning smell before. I do not like hearing that either. My guess would be that you have a motor problem. It would be a guess if you can not catch it when the problem actually occurs. I hope you can easily find and fix the problem. Steve

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