Kenmore furnace - burner goes out, pilot stays lit


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Old 01-20-13, 02:19 PM
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Exclamation Kenmore furnace - burner goes out, pilot stays lit

I have a Kenmore furnace (model NTC6100GFA1).

Once in a while I find it running, but the main burner is not lit. The pilot is still lit. The pilot light acts properly (ie - on when thermostat is calling for heat, off otherwise).

I'm losing my mind. It's an intermittent problem.

Here's what I've tried and determined:

Replaced filter. Thermostat batteries seem fine (haven't replaced them yet). I have only 2 wires from the thermostat... just heat on/off, no "fan only" or anything like that.

There appears to be 2 circuits with the rollout/interlock/pressure/etc sensors. It is NOT an issue with any of these, as when I disconnect the loop, the pilot & burner immediately go out. When reconnected, both the pilot AND burner immediately re-light.

The last time it stopped working, I pulled the bottom cover off and played with the interlock switch to see if I could find a pattern. There are a few things that happen when I release the interlock switch, and depress it again. It doesn't seem to matter how long I wait between presses.

1) The pilot lights, but the main burner does not.
2) The pilot lights, then the main burner lights, but the main burner goes out within 2 seconds.
3) The pilot lights, then the main burner lights, bu the main burner goes out 15+ seconds later.

Other observations:

-Once working, it appears to work until the next time the thermostat calls for heat (ie - if the burner hasn't gone out within 30 seconds of igniting, it won't).
-This furnace does not have a flame sensor (nor would that explain this problem, as sometimes the pilot lights, but the main burner doesn't)
-There is no smell of natural gas.
-There is no "click" or audible noise coming from the gas valve when the main burner quits (unlike the very audible click when the pilot lights).
-Sometimes when the main burner goes out, it seems to take 3 seconds (ie - I can hear "ok it's going to quit now" based on flame sound, then over the period of 2-3 seconds it goes down, then blip, it's out). Other times, like when it quits shortly after lighting, it's a much faster "fwoosh" out.
-The gas valve doesn't appear to have separate "main burner" and "pilot burner" connections that I can test.

Any advice?
 
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Old 01-20-13, 02:23 PM
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Old 01-20-13, 02:28 PM
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http://icpindexing.toddsit.com/docum...nd%20Parts.pdf

The Honeywell smart valve is your most likely culprit.
 
 

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