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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

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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.

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