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Lennox Whisper Heat G20 burners don't always light

stacia

Premium Member
Joined
Jul 26, 2012
Messages
53
Location
Kansas
Model Number
G20
Brand
LG
Age
More than 10 years
Our furnace has an issue with the burners not always kicking on. They light sometimes but at others they will try to light for an hour or so, then stop and reset for 5 minutes then try again, and will take several tries before finally lighting and running correctly.

Everything seems to be working normally except the burners lighting. When the temp on the thermostat gets low, we hear the click as the furnace turns on, then it buzzes (which I think is normal, I've heard the buzz for years) for about a minute, then the blower comes on, then we wait for the louder click and the whoosh of the burners lighting. Sometimes that whoosh just doesn't happen. The pilot light will be on but then click off when the burners don't light.

This has happened on this unit twice in the past (2008 and 2014) and both times it was fixed by a replacement of the ignition module. The original Johnson ignition module isn't made anymore so we have gotten a Honeywell both times instead, from the local repair place. So this time we bought a new Honeywell universal S8610U, same as the one we had before, and installed it, but this time it didn't help. The furnace behaves exactly as it did before we changed out the ignition module, i.e. it comes on normally about half the time, the other half it has to try a few times before it comes on.

The LED error code we get on the ignition module is just the two flashes indicating a 5-minute delay for reset and retry, which doesn't help much with diagnosing the problem.

We weren't sure the ignition wire was fully heating up so we used some compressed air to try to clean that area, and it did turn on normally right after that for a while, but after several hours it was back to the burners not always lighting.

Any thoughts on what this could be?

(Sorry I put LG in the brand drop-down below, there wasn't a Lennox option so I didn't know how to handle that)
 

stacia

Premium Member
Joined
Jul 26, 2012
Messages
53
Location
Kansas
Sorry to bump this thread but I wanted to clarify, when I said the burners will "light sometimes but at others they will try to light for an hour or so," I misspoke, I meant to say that they will light sometimes but if they don't, they will try again after 5 minutes, not after an hour.
 
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