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ISSUE PLEASE HELP: Goodman Furnace Model: GMS951155DXA

laszlonovak
laszlonovak Member Posts: 7
in THE MAIN WALL

The furnace blower motor is running for 3 minutes turning off for 30 seconds and then repeats the cycle over and over while the thermostat is off and the compressor outside is off. We installed a new board, White Rogers/ Emerson Single-Stage Hot Surface Ignitor Integrated Furnace Control Kit Model # 50a55-743 three different times within a few weeks. We replaced one last night and everything was running fine until 24 hours later. Is the board failing? What is going on? We have a Goodman Furnace Model: GMS951155DXA.

Comments

  • mattmia2
    mattmia2 Member Posts: 10,879
    edited September 14

    does it do it if you disconnect the thermostat wires ate the furnace?

    is it some sort of "smart" thermostat?

    laszlonovak
  • laszlonovak
    laszlonovak Member Posts: 7

    it's a digital thermostat - Honeywell - if I turn it off or remove the face the fan still runs; I have not tried disconnecting the thermostat wires at the furnace

  • mattmia2
    mattmia2 Member Posts: 10,879

    is it in an attic? is the fan control for the heat a thermostat rather than a timer?

    laszlonovak
  • Teemok
    Teemok Member, Email Confirmation Posts: 677

    Is there an led flashing a code on the board? Seems like the fan is a signal pattern. The fault code will tell you more, like open limit or something.

    laszlonovakHVACNUT
  • laszlonovak
    laszlonovak Member Posts: 7
    edited September 14

    It's in the attic and I'm running the AC (compressor is fine). It's a thermostat. I'll have to look into the flashing led code. The supply house I got the board from had 3 other boards sitting there for warranty. Makes it look like faulty boards.

  • laszlonovak
    laszlonovak Member Posts: 7

    ok, my hvac guy said the times he went up there it was steady red light. no codes.

  • Teemok
    Teemok Member, Email Confirmation Posts: 677

    Either the board is doing it for a good reason (unknown) or a bad reason (it's fauly)

    OR

    The thermostat is causing it for some reason.

    Eliminating the thermostat as a possible cause would be my first move.

    HVACNUT
  • laszlonovak
    laszlonovak Member Posts: 7

    We installed a new thermostat. I found this. Could this be it? I'm in the desert so it gets hot.


    The hot attic is causing the the temperature in the furnace to reach or exceed 120 F. 

    When the temperature in the furnace reaches 120 F, the Fan Switch - Thermal , (FST on the wiring diagram) closes and turns the blower on

     . The blower continues to run until the attic cools overnight.

    mattmia2
  • laszlonovak
    laszlonovak Member Posts: 7
    edited September 14

    So it was 76 in the house and I set it to 75. The compressors and furnace blower came on, ran until 75 and turned off.The on off cycling stopped. I then put it back up to 76 and the furnace blower came on again and started the on off cycling again. I turned the thermostat to off and the blower keeps cycling.

  • HVACNUT
    HVACNUT Member Posts: 6,320
    https://forum.heatinghelp.com/discussion/comment/1810403#Comment_1810403

    When you say the "furnace blower came on", you mean the induced draft motor, or the blower motor? If you mean the blower motor, have you noticed if the IDM also comes on?

    And the issue is the same after replacing the board?

    I don't see any limit in the furnace closing at 120° at the end of a cooling cycle.

    If it's a steadily repeating cycle like you say, then something is telling it to do it.

    Is the fan mode on the thermostat set to Auto, On, or Circulate? I would guess "Circulate", but you say if you remove the thermostat from the sub base, it still happens. Are you sure? Because when the fan circuit is interrupted, there could be a "Fan Off" delay in the furnace. Have you waited 5 minutes with the thermostat removed?

  • Teemok
    Teemok Member, Email Confirmation Posts: 677
    edited September 14

    "So it was 76 in the house and I set it to 75. The compressors and furnace blower came on, ran until 75 and turned off.

    That's a rare thermostat with a very tight differential. This might be a misinterpretation of happenings. You can guess about tea pots in Saturn's rings but good testing should lead to a cause fairly rapidly. Tossing new parts at it can sometimes just confuse things, wasting time and money. Thermal control of the blower by an "FST" doesn't look to be applicable to the model. Strange things are afoot at the circle K.

    laszlonovak
  • mattmia2
    mattmia2 Member Posts: 10,879
    edited September 14

    If the blower for the heat is controlled by a thermostat in the furnace it doesn't care if there is a heat call or not, if the furnace gets hot enough to close the thermostat the blower is going to turn on.

    if that is what is happening noting is wrong other than the furnace is located in a very hot attic. this is probably why furnaces of the past 30 years or so use a timer to control the blower during a heat call.

    laszlonovak
  • Teemok
    Teemok Member, Email Confirmation Posts: 677

    @mattmia2 I see no such switch in a GMS9 furnace. Maybe I'm wrong but I thought thermal switch control of blowers was over a long time ago. Its timed operation off the control board.

    laszlonovak
  • laszlonovak
    laszlonovak Member Posts: 7
    https://forum.heatinghelp.com/discussion/comment/1810416#Comment_1810416

    When the blower motor comes on the IDM does not come on; we don't have Circulate for the thermostat we only have Auto and On and it's on Auto; waited 5 minutes after the circuit was interrupted, and the fan kept going

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