Furnace Fan doesn't work on its own

Discussion in 'HVAC' started by avxflyer, Dec 31, 2011.

  1. Dec 31, 2011 #1

    avxflyer

    avxflyer

    avxflyer

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    I'm trying to run the fan on my furnace and it's not working. The heat and AC work fine and the fan turns on with those options, but not when I simply turn the fan on. I jumpered the G and R wires at the thermostat, but still nothing. Then I jumpered the G and R on the control board and there is a click. I'm assuming this is a relay. The fan still doesn't start. I had the whole control board replaced about a year ago, but never tried the fan on its own. The furnace is a Lennox about 13 years old. The control board has a flashing red and flashing green light. Both are flashing at the same time. Not sure if this is normal or indicates a fault. Any insight on what is going on?
     
  2. Dec 31, 2011 #2

    paul52446m

    paul52446m

    paul52446m

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    When you jump G and R on the board, the board should start the blower.
    Check the wiring on the board, one blower wire on the heat post, one blower wire on the cool post. Do you have a post marked const. blower?
    Usually this is done through the stat. Some furnace's the fan on is cool speed and some it the heating speed. Paul
     
  3. Jan 1, 2012 #3

    avxflyer

    avxflyer

    avxflyer

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    Based on what you wrote, you got me thinking about the wiring. I pulled up the installation manual for the ignition control kit which was installed when the furnace was fixed a while back. I still had the old part as well. The kit contained a board with a separate spade connection for the blower while the original board did not. I guess I not only overpaid for the board, but overpaid for the technician too! There was a jumper cable in the box to provide a connection between the heater blower speed connection and the fan connection. It works now. Thanks for your help!
     
  4. Jan 1, 2012 #4

    paul52446m

    paul52446m

    paul52446m

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    glad you got it fixed. Paul
     

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