Gas Furnace - Blower Motor Not Running

Gas Furnace

Re: Blower Motor Not Running

The furnace control board energizes the fan motor through line-voltage outputs for both heating and cooling.

There are two fan speed outputs on the control board: Cool and Heat

• On a call for cooling "Y", the control board should immediately energize the Cool output.
• On a call for heating "W", the control board should energize the Heat output after the burners ignite and the heat chamber has time to warm.
• The control board should also energize the Heat output on a call for Fan-Only "G".

1. Check Furnace Power

• Check for 120VAC at the control board between "Line" and "Neutral".
  • You should have to push-in the blower door switch to get power.
    • No Power --> Check SSU fuse and breaker

2. Check Low Voltage

• Check for 24VAC at the control board low voltage terminals between "R" and "C".
  • No Power = Blown Low Voltage Fuse or Bad Transformer
• Install a jumper wire from "R" to "G" (should energize HEAT fan output).
• Check for 120VAC between HEAT and Neutral.
  • No Power = Bad Control Board
• Install a jumper wire from "R" to "Y" (should energize COOL fan output).
• Check for 120VAC between COOL and Neutral.
  • No Power = Bad Control Board

3. Check Fan Motor/Capacitor