Lennox G50UH(X) Watchguard issue


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Old 03-06-11, 06:01 PM
J
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Lennox G50UH(X) Watchguard issue

Hello,

I have a Lennox G50UH(X) that has all of the sudden developed an issue with going into Watchguard mode upon start up. During the start up cycle the ignitor glows red and then starts the burners with no problem. The burners will fire for 30-60 seconds before shutting down. The LED status lights read a quick "low flame signal" status when the burners shut off. This process repeats 5 times before the furnace goes into Watchguard mode and no longer operates.

I've tried cleaning the flame sensor and connection points with steel wool, and the problem still persists. It is not an intermittent problem, the furnace has not been working for a few days. Any thoughts on what could be causing this?

Any suggestions would be greatly appreciated!

Thanks,
John
 
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Old 03-07-11, 03:41 AM
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DO you have a meter that will read DC micro-amps? This is what is needed to check the actual flame signal. For whatever reason, it has been my experience that Lennox has bad flame sensors. You can also check the AC Voltage that is going to the flame sensor.

2 possible problems - Flame Sensor or control board are the 2 most likely culprits.
 
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Old 03-07-11, 08:38 AM
J
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Thanks for the advice. I'll look into getting a meter.
 
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Old 03-07-11, 01:10 PM
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Try removing & cleaning the flame sensor (figure 8, pg. 7) of this manual: http://www.cozyparts.com/Lennox-Part...09-01-2003.pdf

I prefer using Scotch-Brite for cleaning but VERY fine sandpaper will work also.
 
 

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