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View Full Version : Thermostat not turning on fan when set to AUTO


selisky6
Jan 20, 2008, 11:04 AM
My problem is a little bit different then those I read about. My thermostat just started not to turn my fan on when the heat starts up, causing it to shut off. The only way my heat works now, if I manual turn the fan setting from AUTO to ON. Which causes my fan to run all day. Please help! It was 51 degrees this morning.

hvac1000
Jan 20, 2008, 11:29 AM
Sounds like you have a bad heat sequencer/fan control. Use the wiring diagram on the unknown brand furnace and track down this part. Replace or test with your meter then replace.

selisky6
Jan 20, 2008, 12:49 PM
Sounds like you have a bad heat sequencer/fan control. Use the wiring diagram on the unknown brand furnace and track down this part. Replace or test with your meter then replace.


What does this part look like. I think mine is black with a small toggle switch. Is this part right. If sso where could I get a replacment part. Thanks for getting back earlier.

hvac1000
Jan 20, 2008, 04:48 PM
Tell us more about your furnace.
Gas or electric
Brand
Brand model number.

selisky6
Jan 21, 2008, 08:30 AM
Lennox G23Q2/3-75-4 serial #5896M25583

hvac1000
Jan 21, 2008, 08:43 AM
((My thermostat just started not to turn my fan on when the heat starts up))

What fan are you talking about? The little combustion air fan or the blower fan?

selisky6
Jan 21, 2008, 09:17 AM
Blower Fan

hvac1000
Jan 21, 2008, 10:34 AM
Since the blower fan will not come on when the furnace is on in the automatic setting you have a problem with the fan control. I have no drawings for lennox but if you look at the wiring diagram on your unit it should show some kind of a fan control. At least you are not out of heat since you can turn the blower on and leave it run.