Lennox g40uh blower won't turn on

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Old 11-28-13, 09:34 AM
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Lennox g40uh blower won't turn on

Hi,

I've got a Lennox g40uh gas furnace. The furnace will ignite, but shuts off after ten minutes or so, I guess when it starts to overheat. The main blower motor never comes on. The thermostat has a switch to turn the fan on separately, but that doesn't work either. When I turn on the fan switch at the thermostat I can hear the furnace clicking like it's starting up, but the fan never comes on.

There is a large capacitor on the front of the blower, separate from the rest of the circuit board. When I poked around with a current detector, I noticed that one wire going to the capacitor has current, but the other does not. Could this be the problem? I can't remember my electrical theory well enough to know if one or both wires going to a capacitor should have current during normal operation.

What should my next step in troubleshooting this be?
 
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Old 11-28-13, 10:25 AM
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Welcome to the forums.

First turn the power off and see if the blower wheel is free...... not bound or frozen.
If it's ok you may want to change the capacitor next since you've already verified power to the blower motor.

Usually is the cap is defective you'll hear the motor hum but not start.
Is the motor hot ?
In some instances you can carefully try turning the blower with a stick to see if it starts spinning.
 
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Old 12-21-13, 04:07 PM
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For the benefit of anyone else with the same problem, it turned out to be the capacitor. You can get replacements on Amazon or eBay.
 
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Old 12-21-13, 04:20 PM
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Thanks for stopping back. Glad the problem is fixed.

In your case it was the capacitor. That is not always the case.

Also, when using an inexpensive replacement capacitor.... you may find yourself replacing it in a year or two.
 
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