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 Repairing and Servicing Lennox Products
 Repairing / Servicing Lennox Gas Furnaces
 G26Q3/4-100-3 Inducer Motor
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jasoncw

3 Posts

Posted - 04/21/2011 :  09:24:23 AM  Show Profile  Reply with Quote
For the past couple months, the inducer motor would start, then quit after about 2 seconds. Then nothing. It would stay on, however, if I cycled the thermostat. It reached the point as of 2 days ago that no matter how many times I cycle the t-stat or power cycle the furnace, it will now only kick on for about 2 seconds, then immediately shut off.

I had a tech come by last night. The first thing he noticed was the inducer motor is very loud (buzzes). That was his first instinct that it was bad. After trouble shooting for a bit, he jumped the t-stat and it kicked on and stayed running. He then figured it could be a bad t-stat. It is a Honeywell electronic programmable. I replaced the batteries in it, and what do you know, it stayed running.

We went to bed, and I woke up to a chilly house. It is right back to where it started. I even swapped the original Lennox manual t-stat back in with the same results.

The LEDs are simultaneously flashing slowly, which indicates normal operation in non-heat mode. Of course, the t-stat is in heat mode, so could it be a bad t-stat wire? Board? Or inducer motor?

Thanks in advance for any help.

Jason

Cozy.Support

5761 Posts

Posted - 04/21/2011 :  09:44:54 AM  Show Profile  Reply with Quote
First, make sure the thermostat is calling for heat. You will need a volt meter. Confirm that you have 24 VAC between "C" and "W" at the low voltage thermostat wire connector strip on the circuit board. This is the voltage that is required to tell the furnace to turn the heat on.

Next, let the furnace try for ignition. If the induced draft blower does not stay running, wait a while and see if the control board sets a diagnostic code.

If you get a induced draft pressure switch code on the LED lamps and the inducer is not running, measure the voltage output from the circuit board to the inducer. The voltage should be about 115-125 VAC. If you get some other code on the board, let us know what it is.



CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx
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jasoncw

3 Posts

Posted - 04/21/2011 :  12:52:11 PM  Show Profile  Reply with Quote
Thanks for the help so far.

I am reading 0.0 VAC between the C and W terminals on the furnace when the thermostat is calling for heat.

I am reading 120 VAC between the board and the inducer, but only for the two seconds or so that it is running before it shuts down.

After the inducer shuts off, I receive the same LED code, which is both flashing slowly together. This indicates normal operating in a non-heat cycle.

Does this mean that both of my thermostats are bad?

Also, is it common for the inducer motor to buzz relatively loud?

Thanks again for the help.

Edited by - jasoncw on 04/21/2011 12:53:04 PM
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Cozy.Support

5761 Posts

Posted - 04/21/2011 :  1:58:50 PM  Show Profile  Reply with Quote
Without 24 VAC at (between) the W and C terminals, there is no call for heat as far as the furnace is concerned. You need to check the thermostat and thermostat wiring.




CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx
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jasoncw

3 Posts

Posted - 04/21/2011 :  2:08:30 PM  Show Profile  Reply with Quote
The W terminal is the white wire from the thermostat, and the C terminal is the white wire for the furnace. Does that sound right?
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