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tevans 11-15-2006 01:20 AM

Gas furnace not lighting, but damper moves
I have a Lennox Whisper Heat forced hot air gas furnace. The 1st few times used it this year the blower would stay on long after the burner turned off and the heat stopped coming out. It would be blowing cold air out of the vents. This could be "solved" turning off the power to the furnace, which seemed to reset it.

Now it will not light. The damper moves in response to the thermostat, but no ignition or flames, or indications of an attemped to light.

Thoughts on whats wrong/how to fix it? Something in the temp/heat/flame sensor control in the furnace.

mdshunk 11-15-2006 05:56 AM

Those dampers get "sticky" and don't turn the whole way to switch the switch inside them. You can try to rotate it manually just that little bit further and see if the furnace fires. If it does, replace that damper motor assembly.

tevans 11-15-2006 09:32 AM

Damper is opening all the way to its stop. I also hear a solenoid click just before it gets to full open, but no firing.

#CARRIERMAN 11-15-2006 10:40 AM

Hi tevans

Mdshunk was right about the dampers, but one of the most common failures other than that is the ignition control on this particular furnace. If yours still has the original Robertshaw, replace it with a Honeywell s8610u1003. If you have any further problems, let us know

Good luck

tevans 11-15-2006 07:24 PM

I have heat!!! and the blower cycles correctly. Thanks for the great advice.

A couple of other questions if I may:

I want to replace my old battery powered mechanical setback thermostat (I'm tired of the clicking clock sound). Recommendations?

Any furnance PM you suggest, other than changing the filter?

Thanks again


#CARRIERMAN 11-15-2006 09:01 PM

Hi tevans

The thermostat my company sells as our primary replacement line is the White Rodgers 1F80-361 for a programmable thermostat. This is a very affordable and a very user friendly little thermostat. We did some quick calculations on the number of these we have installed since we started using them. We have got almost 8000 of them out there, and only about 50 have failed. Most failures were due to maintenance of batteries, there were some that were just duds also. As far as maintenance I would like to reccomend you have someone come in at least every heating season and check heat exchanger with a spray chemical called HEAT. The particular furnace you have has had some problems with heat exchanger failure, we just installed a new heat exchanger in one about a week ago that was only 12 years old. Your furnace should have a twenty year heat exchanger warranty if needed. The other important part is to keep the pilot and main burners cleaned at least every other heating season. Let us know if we can help any further.

Good luck

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