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Old 05-21-2010, 12:30 PM   #1
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fan won't run alone


I turn the fan switch on the thermostat to "on" but the fan will not run. When running the air conditioner or heater, however, the fan seems to run and pushes the cool and hot air. If anyone has any ideas as to the problem, I'd appreciate them. Thanks.

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Old 05-21-2010, 03:52 PM   #2
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fan won't run alone


What is the brand and model number of your furnace?

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Old 05-21-2010, 04:02 PM   #3
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fan won't run alone


its a Lennox 80 MGF Series Gas furnace

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Old 06-01-2010, 12:57 PM   #4
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fan won't run alone


Anyone else have any thoughts? Thanks!
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Old 06-01-2010, 03:03 PM   #5
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fan won't run alone


Check the G terminal on your furnace and thermostat, make sure the wire is connected tight.
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Old 06-11-2010, 03:19 PM   #6
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fan won't run alone


The G Wire is tightly connected at both the thermostat and the furnace. I wonder if the thermostat is bad (although everything else seems to work fine)?
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Old 06-11-2010, 04:38 PM   #7
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fan won't run alone


Remove thermostat. Jumper from R to G. If the fan runs when you do this. Its the thermostat that is bad.
If it still doesn't run. Do the same jumper at the furnace board. If it still doesn't work. Its the board.
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Old 06-11-2010, 06:05 PM   #8
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fan won't run alone


There were a few of those units that did not have a continuos fan capability from what I remember. Depends on the series of unit. Uses the Y terminal to energize the fan relay. Lennox is known to switch boards thru different series of the same unit. Post the complete model # and I may be able to look it up.

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