Lennox G50UH(X) Inducer Motor Problem


Old 12-29-12, 09:18 PM
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Question Lennox G50UH(X) Inducer Motor Problem

While visiting my Mom for the holidays, we've been having trouble with her furnace and I haven't come across any good information about this problem or how to fix it.

When the thermostat calls for heat, the inducer/combustion motor cycles off and on several times before the ignitor kicks in. Once I have a flame, there are no other problems. It's pretty annoying hearing the relays clicking so much, but that seems to be the only problem.

Before this, I have already cleaned the flame sensor which was looking a little grimy. I've also checked for any error codes and came up empty. The LEDs show that everything is operating normally.

Any ideas?
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Old 12-29-12, 10:15 PM
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I'd check the stat.

Does the furnace start normally if you remove the stat and jump R (24VAC) to W (heat terminal)?
Old 12-30-12, 02:43 PM
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When the thermostat calls for heat, it does so by taking voltage from the R terminal on the furnace and applying that voltage to the W terminal on the furnace.

Any time you have 24 VAC being applied to the W terminal the inducer motor should turn on and stay on.

So the proper way to check what is happening is to use a multimeter to see if the inducer motor is staying on when there is 24 VAC to the W terminal.

If you do, that suggests that the thermostat isn't switch on voltage to the W terminal reliably, or perhaps the voltage to the R terminal is being interrupted.

If the voltage to the W terminal is on and the inducer motor isn't starting and staying on reliably, you have a bad circuit board that needs to be replaced.

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