Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Blower fan goes on and off

maxg Member Posts: 4
Blower fan turn on and off repeatedly and fast while heat is on, ive tired some small things but nothing seems to be working.


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,132
    You almost couldn’t provide less information to receive help.

    -blower fan on what?
    What type of equipment? Gas/oil/heat pump? New/old? Make/model #?

    -define repeatedly.
    New problem or old? How long has it been going on?

    -define fast as it relates to your issue

    -what 'small things' have you tried?

    Why haven’t you called a tech to check your system and diagnose the problem?
    EBEBRATT-Ed Member Posts: 13,448
    If this is a hot air furnace check the fan/limit switch if it's an older unit. If it is you may have an auto/fan switch on this control. Switching it ti on may run the fan so you can get heat until you get it fixed.

    As @STEVEusaPA said, we don't have crystal balls or x ray vision. Gotta give us more information
  • maxg
    maxg Member Posts: 4
    I’m pretty sure it’s a Goodman GMP075-3

    Blower fan on forced air gas heater, heater is 19 years old. Problem hasn’t been going on for 2 weeks, system turns on fine a few seconds the blower turns on, a couple minutes into heating the blower fan well repeatedly turn on and off every two seconds.

    As in what I’ve tried, redoing connections at thermostat to see if one was loose.

    Changed thermostat to a new nest thermostat
    HVACNUT Member Posts: 5,028
    Flame is established, time delay brings on the fan. Then during the fan cycle it (the fan) will repeatedly turn off and on every 2 seconds? I dont think I've ever come across that.
    Does the flame and induced draft motor stay on during this?
    I think it's a problem with the board. Unless it's the fastest limit in the west.
    Do what @EBEBRATT-Ed said and switch the thermostat to "fan on" if its wired for it. Is there A/C? Switching to fan on will (should) run the fan at constant high speed.
  • DZoro
    DZoro Member Posts: 1,048
    At the furnace unhook the G and the Y (if used). Then see if the furnace continues to act up.
    JUGHNE Member Posts: 10,579
    IIRC, there was a posting some time ago like this.
    The fan board had bad solder joints on the back side, it was hit and miss operation of fan.
    That HO looked at the back side of the board and it was obvious.
  • maxg
    maxg Member Posts: 4
    I’ve switched back to my old thermostat for the time being and no more issue has occurred, could this be due to there not being a common wire?
  • maxg
    maxg Member Posts: 4
    edited April 2019
    There is a jumper form the RC to the RH, a G and lastly W. I’ve been reading up on smart thermostats and they say that they need constant power or a common wire to run smoothly, I’ve found out the nest well “pulse” the heating system to charge itself when the battery runs low, due to only getting a charge when the system is running.
  • pecmsg
    pecmsg Member Posts: 3,885
    Another NEST Issue?

  • clammy
    clammy Member Posts: 2,912
    Check your air filter for starters and if you upgrade to a depo 1 inch hepa filter remove it most likely to restrictive and is cycling the unit on it limits .how I know cause I had a few do Good doers who did the same and called me after to trouble shoot and all I did was remove that filter and install a30 day throw away and promblem solves .if that does not work un wire your thermostat jump at unit and see what codes come up on the controller if equipped and if it goes off on safety also u say it’s a 2 stage unit make sure your stat is set above the set point .some older staged stuff has a timer for 1 stage to limit short cycling between 1 and 2 Nd stage if not clean and chk flame sensor and chk air switch .peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
    EBEBRATT-Ed Member Posts: 13,448

    Shut power off at the furnace. Install a jumper wire between R & G. Turn the power on. The fan should run all the time.

    Try this and then we can move to the next step. Or call a professional
    HVACNUT Member Posts: 5,028
    But the issue was there even before the Nest, correct?
    Could still be the board or poor connection somewhere between the board and the thermostat. Tighten all the low volt terminal screws and or wire nuts.
    Do you have an electrical meter to check continuity?
  • DZoro
    DZoro Member Posts: 1,048
    He removed the Nest and problem went away.... He didn't have a common wire to the Nest....