My Goodman furnace burners ignite fine but fan never starts. Have I got a bad fan motor? LED blinks 4 times for High Limit Switch. I've removed the switch and shaking it softly you can hear the internal part moving freely – but perhaps it's still faulty and should be replaced (only $9 on amazon). After the burners run for a period of a minute or so they kick off – which I believe should happen because the fan isn't running – just my thoughts. Any help would really be appreciated.
Goodman gmv950704cxa – installed in 2007
Best Answer
I have a similar Goodman furnace and have done troubleshooting on it for similar problems.
Your thought is correct - if the burner fires but the blower does not start, that will cause the burner / heat exchange to overheat. When the high limit trips, that is normal and the switch is doing it's job.
Some possible causes and troubleshooting for the blower non-start:
Bad capacitor (the PSC blower motor needs the capacitor to start/run). Disconnect the cap and test with a multimeter on Ohms setting.
Blower stuck The blower squirrel cage should turn freely if you push it by hand.
Bad motor Test with a multimeter on Ohms, there should be low resistance on each winding. Infinite resistance (open) on a winding is bad. You might try selecting a different speed.
Bad control board Test with a multimeter to see if the board is supplying power to the motor. Note there will be different terminals powered depending on the selected speed.