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Istivan 10-04-2010 05:16 PM

Intermittent Flame
I have a Lennox Whisperheat. Yesterday I could not get the thing to flame. All through the night, no flame, but this morning it fired up, heated the house, shut down, did this 3 times. Now this evening I cannot get flames again.

I can hear the igniter click, but it does not always ignite the furnace.

Any ideas out there as to what this might be?

Thanks a lot and take care.

yuri 10-04-2010 05:58 PM

It should not click but make a buzzing sound when trying to light the pilot.

Istivan 10-06-2010 11:21 AM


As everyone I hate diagnosing an intermittent problem.

And the "clicking" is from the igniter trying to light the flame, so yes it is supposed to click.

The furnace works ok for the most part. Having an electronic thermostat I set it lower at night. Upon trying to increase the temperature to stay with the schedule, the furnace will not light. It clicks for a while and then stops. Then attempts again a little while later and then stops.

However, if I turn off the power to the furnace and let it sit for about 5 minutes and turn it back on, the furnace works fine all day until the next morning when the thermostat cycles the temp back up for the daytime program.

Any ideas out there?

TimPa 10-06-2010 03:05 PM

"the furnace works fine all day until the next morning when the thermostat cycles the temp back up for the daytime program"

the furnace is calling for heat here, it doesn't know if it is a little heat or what time of day. if the furnace is trying to light when calling for heat, the t-stat is doing it's job, and the problem is likely in the furnace. do you get a failure code flashing?

Marty S. 10-06-2010 04:53 PM

Ignition module sparks then sends 24 volts to pilot side of gas valve. Pilot then lights and flame sensor needs to carry at least 1 microamp for the module to send 24 volts to the main side of the gas valve. You'll need to check that sequence of operation and find out what isn't happening.

Istivan 10-11-2010 12:26 PM

Thanks for the help and tips.

Here is what I found.

My igniter was dirty. So I cleaned that to get a more true spark.

My flame sensor was flaky so sometimes it would allow the furnace to fire, sometimes it would not.

The flow valve for the gas to my pilot was getting clogged. Replaced that and everything seems to be working optimally now.

So was 3 almost bad items causing me the intermittent firing.

Thanks again everyne and happy repairing.

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