gas furnace problems


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Old 01-31-10, 05:46 PM
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gas furnace problems

i went to look at a buddys gas furnace you set the thermost up to kick it on the igniter clicks the furnace lights and 12 seconds later it kicks off can some one give me a hint of what it could be im thinking the flame sensor but it does light though
 
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Old 01-31-10, 07:27 PM
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Cleaning the flame sensor would be a good place to start. With very fine sandpaper or steel wool, give it a gentle cleaning lengthwise. Then reinstall and see if that cures his problem. The main burners will light, but when the flame sensor fails to confirm the flame, the furnace will shut down.
 
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Old 02-01-10, 04:05 PM
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cleaned it up but still the same thing whats next i thought it was it because it ran the first time for like 3 minutes but then went back to the 12 second deal like in my first post
 
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Old 02-01-10, 04:25 PM
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What ignites this furnace?: A sparker that lights a pilot? Or a sparker that lights a (often single gun)burner, directly? Or a glow coil that gets brighter and brighter for like 20-30 seconds, before you hear the gas valve click on?

When it clicks off does the inducer fan keep running? -at least for a while?
 
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Old 02-01-10, 07:15 PM
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it is a igniter it clicks and then it lights i believe about 6 rails runs for about 12 seconds then it shuts down i belive the inducer fan keeps running
 
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Old 02-01-10, 10:07 PM
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Originally Posted by nixonnic
i believe about 6 rails runs for about 12 seconds then it shuts down


What?










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Old 02-02-10, 04:42 PM
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Direct spark, eh? Our commercial Lennox air handlers have that, with the multiple burners. With those, our main issue has been failure of the ignition modules. We've now had to replace about 4 out of 8, so far.

But since you do not have the luxury of swapping parts as I do - you might want to try cleaning the burner over next to the flame sensor to make sure flame is getting to it good. Also, if the flame sensor wire has a pin connector at the board or module end, remove that connection and reinsert. Sometimes pin connectors expand, oxidize and lose their abilty to make good connection. Spade connectors I have found aren't as bad that way, usually. And if a similar type male-female pin jack connector is involved, unplug then replug it back together. Also make sure that if module or board is grounded, that ground connections are good.
 
 

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