Electric furnace blower motor doesn't turn on once in a while

Discussion in 'HVAC Heating & Cooling' started by Hyrules, Mar 7, 2014.

  1. Hyrules

    Hyrules New Member

    Messages:
    16
    Location:
    Quebec
    Hi everyone,

    I'm having a problem with my Broan Electric furnace lately. Sometimes the blower motor doesn't want to switch on.
    Sometimes it works fine for a while but this morning it didn't want to turn on. The heating elements are working
    because I can feel the heat from the furnace but the motor does not. I tested the bottom sequencer but afaik
    it is good. There is no electronic control board in there. It's all mecanic. Could it be one of the relays that's going
    faulty ? If so would it be the 24V relay or the 240V relay ? Right now I've been able to have it run because I left
    the breaker of the furnace off half an hour to test the sequencer. I know the motor is working because I can switch
    it on on the furnace on both low(normal) and high speed. Any help would be appreciated.

    Thanks.
  2. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX
    What kind of blower is it. Is it cap start/run ? How old is it ?

    A model number may help you to get a better answer.


    Good Luck on your project. If it can be broke, then it can be fixed.
  3. Hyrules

    Hyrules New Member

    Messages:
    16
    Location:
    Quebec
    Last edited: Mar 7, 2014
  4. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX
    Your pdf did not work for me. But I found some info.

    You may want to check your T-Stat and make sure it is set for a electric furnace.

    If it is set for gas, it may delay blower start. Depends on the thermostat.

    If the T-stat has batteries, you may want to check or replace them.

    Check the cap if you have a way. Make sure it is getting voltage.

    Running the Coils without air moving, can be a big problem.


    Good Luck.
    Last edited: Mar 7, 2014
  5. Hyrules

    Hyrules New Member

    Messages:
    16
    Location:
    Quebec
    Oops my bad for the link. I changed it now it should work.

    This kind of furnace has a built in mechanism that triggers itself after a couple of minutes of the heating element are on. The thermostat does not control the fan. It just
    sends a call for heat signal to the furnace.

    Thanks for your help Don. I have replaced the T-stat batteries. I'll wait and see if the problem reoccurs.
    Last edited: Mar 7, 2014
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,819
    Location:
    New England
    With the power off, can you access the fan to try to manually rotate it? If the bearings are bad, even just a sticky spot, when it tries to start, it may not. If it happens to stop where it can turn enough before hitting that 'bad' spot, it will start and run normally. How the fan starts is probably with an internal relay. The contacts could be bad, or the control logic, or maybe a safety interlock.
  7. Hyrules

    Hyrules New Member

    Messages:
    16
    Location:
    Quebec
    The problem only happen one in a while. I can make the fan spin if I push the fan button on the furnace or the continuous ventilation mode button. Chances are it might be a relay going bad like you said.
  8. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX

    After looking at your working PDF, the blower is connected to Two relays, and the fan speed changes depending on the Stages being used.

    Are you using a two stage or outdoor thermostat ?


    Good Luck.
    Last edited: Mar 8, 2014
  9. Hyrules

    Hyrules New Member

    Messages:
    16
    Location:
    Quebec
    Outdoor thermostat no. Two stage i don't believe so. The elements start to heat and after 3 minutes the blower kicks in. The other speeds are for continuous ventilation on low speed and the fan button with is high speed.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,819
    Location:
    New England
    IF the system relies on a heat sensor switch to turn the fan on, it may not be working. The easy way to check that would be to put a jumper across it, but only if you know what you're doing! Be safe. If it is just a time-delay, that switch may not be working. Either way, it should be fairly easy to check with a meter, but again, be careful...if you don't know what you're doing, call someone in that does. It's likely the same relay to turn the fan on, either from your wall thermostat or the internal switching circuit, just gets its control voltage from one or the other source.
  11. Hyrules

    Hyrules New Member

    Messages:
    16
    Location:
    Quebec
    I'm fairly sure that there is no heat sensor it's time delayed. I did test the second sequencer but it came up good. I would have to test the first heat sequencer to see if it is not stuck off or on when it happens. As for the electronics, i have a college degree in it. I know what volts, watts and amps are. I have a fairly good knowledge of electronic circuits but not of HVAC system. As many here i'm a DYI guys who like to save a couple of bucks if he can do the job himself. thanks for the help.
  12. nukeman

    nukeman Nuclear Engineer

    Messages:
    709
    Location:
    VA
    I had a similar issue with my old electric furnace. The problem was with one of the sequencers. In my case, the problem seemed to happen when it was cold. If the heat was off at night and it was cold outside, the heat wouldn't start in the morning. I also tried testing the sequencers, but since it was an intermittent issue, it was hard to know whether the test was accurate. I picked up a couple new sequencers and installed them and everything was good after that point.
  13. Hyrules

    Hyrules New Member

    Messages:
    16
    Location:
    Quebec
    you know nukeman... this is really similar to my problem. This is exactly what is happening. It's generally in the morning that the blower doesn't come on and as I remember the night in question was also cold something like -20ºC ( -4ºF). The thermostat was set to 16ºC ( 60ºF ) and the heat didn't turn on during the night. So in the morning when the thermostat went back to regular temperature the blower wasn't coming on. Thanks for your input it help alot.
  14. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX
    Have you tried to change the setting of your "Season Select" button ?

    You may want to look at the manual notes.


    Good Luck.
  15. Hyrules

    Hyrules New Member

    Messages:
    16
    Location:
    Quebec
    The settings was at mild. It's been that for a while now. This never been a cause of problem for this furnace. We change it when temps get really cold in the middle of winter and set it back to mild when spring is close. The problem appeared long after we set it to mild. Since the last time I had the problem I changed the batteries of the thermostat had the problem didn't reoccur. Might have been the batteries or might happen in a while I don't know. It occurs generally 2 weeks to a month apart more or less if it happen again.
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