Lennox MFG80 problems ( flame sensor rod?)

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Old 02-24-10, 11:33 PM
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Lennox MFG80 problems ( flame sensor rod?)

Oops, its MGF80.
I have been having this problem with my furnace for awhile. After a lot of Googling I found several sites/forums that suggested it may be a dirty flame sensor rod. I would like to try to clean this ( or any other possible DIY fixes). However, I have no idea how to go about finding this and taking care of it. All threads generally go something like this " Oh, you just need to clean your flame sensor rod." " Thanks, that was it!" - as if the what/where/how are obvious to anyone.

Can anyone help me locate the parts on a MGF80 and attempt to clean it ( or anything else as needed)?

Here is the exact problem: The furnace lights but the heat never comes on. The flame will just come on over and over again. If I turn it off and wait about an hour or so there is around a 50/50 chance it will work. If not, it will usually work if I try that a few times. At other times it seemed to come on easier if I turned the fan on ( usually set on auto with the thermostat) first, and then turned the heat on. At worst it would take 2-3 tries and some waiting. Now I can't get it to come on at all.
 

Last edited by NeedFurnaceFix; 02-24-10 at 11:52 PM. Reason: wrong model number
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Old 02-25-10, 10:28 AM
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I presume you have a hot surface ignitor, that glows white hot to light the main burner?


If so, you probably do have a flame sensor, and cleaning it may indeed solve the problem you describe.

The flame sensor is typically on the opposite side of the burners from the HSI. It's a rod that sticks up into the burner flames, and has a single wire from the bottom of the rod that goes back to the circuit board.

Remove the flame sensor and brush it with a wire brush or some fine sandpaper. You just need to cleaning the invisible coating of oxides ---you don't need to cut into the metal of the flame sensor.
 
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