Lennox g34uf-36b-070-08 Works intermittently


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Old 11-09-13, 07:23 AM
J
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Lennox g34uf-36b-070-08 Works intermittently

I have a gas furnace model Lennox g34uf-36b-070-08. the burner seems to ignite only intermittently. This is the sequence of operation when it does NOT ignite:

Thermostat calls for heat operation, and the blower fan starts. I see a glow in the burner area, then I hear a click from the gas valve (this is where it usually ignites) but no ignition. This process repeats 3 more times then the LED's flash slowly alternating, indicating "a)Watchguard - burner fails to ignite or b) lost flame sense 4 times in one heating cycle" according to the diagnostic codes.

To correct this problem I simply turn off the Emergency Shut Off switch for a few seconds then back on and it seems to work. There are several times where simply turning off/on does not work and then I noticed another on/off switch on the gas valve itself. if the first method does not work, switching this on and off seems to then work.

I cannot find a pattern as to when it "stops" working after working for a while. It was working all day yesterday with normal on/off operation as needed, however sometime in the middle of the night it stopped and I woke up to a 58 degree house this morning.

What can be the problem and how can I correct it?
 
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Old 11-09-13, 08:54 AM
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Sometimes the glow plug doesn't get hot enough.had the same issue with a gas dryer once.
 
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Old 11-13-13, 10:14 AM
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So how would I fix that issue if it is indeed the issue. I am not rejecting your suggestion however, I have since noticed that the furnace will go into that same "watchguard" mode in the middle of a heating cycle. For example, the other day, I had to reset it as usual. The house was 62 degrees and thermostat set to 70. The heat was on and climbing, but somewhere around 66 degrees, it stopped working with the LED status code indicating the "watchdguard" mode. (stopping at 66 degrees was just a random temperature. it doesn't always stop at 66, nor always fail in the middle of a heating cycle.)
 
 

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