burners don't stay lit - sometimes - http://www.hvacmechanic.com/ Forums
Original message
| rayne
 |  "burners don't stay lit - sometimes"
, posted Sun 2 Nov 21:17  
My 16 year old furnace recently had a pre-season maintenance. [forced-air, hot surface ignitor and flame sensor]
After that, it ran fine for a day, then started short-cycling. The burners would ignite then quickly go out. Reignite, then go out again. I turned the furnace off and back on and it still short-cycled. I then turned the furnace off for a few hours; after than it ran OK for a day then started short-cycling again.
I have already had to pay for a service call and will have to pay for another one, so I want to get more ideas on what the problem might be.
The tech thought it might be the flame sensor because the reading he took with the meter was erratic. It had been cleaned during maintenance, and he cleaned it again. The furnace ran OK for a day, then started short-cycling again.
If the flame sensor was 'erratic', I would think the short-cycling would be erratic, too.
It seems more like the furnace is getting too hot?
I also thought it might be the rollout switch, but the tech was quite sure it would NOT be that switch. He said the switch would be closed so the burners would not even ignite. The LED is also supposed to flash a code for an open rollout switch. Or if it is in lock-out. The LED shows no error codes.
My last guess is the pressure switch/inducer motor. During service they noted the connection where the tube goes into the inducer was obstructed. They cleaned it and said it would eventually need to be replaced. But that also does not fit the pattern of the furnace working normally after being turned off.
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Replies:
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| jmar
| "Re(1):burners don't stay lit - sometimes" , posted Sun 2 Nov 21:46
if the roll out switch where to open the circuit would be open and the furnace would not run at all. If the aux limit IE limit into heat exchanger where to heat up excessively it would open the circuit until it cooled down, but chances are rare that this would cause the erratic operation. The flame sensor may have a crack in the porcelain which can cause this to happen the micro amp rating varies upon manufactures. If the inducer where clogged the pressure switch would never close and the system would lock out. Suspect but not there and will trust over your opinion a techs and guess that the flame sensor is the casue.
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| | hemikota804
| "Re(2):burners don't stay lit - sometimes" , posted Tue 4 Nov 23:47
Is this a goodman or janitrol furnace horizontal application
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