furnace heat cycles on/off every few seconds


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Old 03-09-07, 12:46 AM
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furnace heat cycles on/off every few seconds

We have a Bryant quietline furnace.I am not sure of it's age but it came with the house that was built in 1970.I noticed tonight that the burners will light,and stay lit for a short while,then go out,then back on.The blower is running the whole time.The furnace shuts off when the desired temp is reached,but the burners keep cycling on and off every 30 or 40 seconds during the whole process.I never had this happen before.What could it be?Can anyone please help?
 
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Old 03-09-07, 01:53 PM
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Sounds like the flame sensor needs to be cleaned.. use scotchbrite pad to clean it.
 
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Old 03-09-07, 02:19 PM
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Wink

Could it be that you hit limit??? Is filter clean and new If AC on it is coil clean ??
 
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Old 03-09-07, 02:39 PM
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Limit

I too suspect a limit problem. Could be a clogged filter, clogged A/C coil, blocked supply or return vent(s), or a bad limit switch.
 
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Old 03-09-07, 03:54 PM
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You have to let everyone know here, who is trying to help you, what kind of time durations we are talking here, for both the on time, and the time it is off for. If the on time is a matter of seconds, let's say...it is doubtful it could limit that fast. Also, once a furnace HAS limited, it would take several minutes before the furnace temp drops enough to take itself out of high limit and fire up again. That is why you have to tell us.

Without knowing, you could have a thermostat issue or control board issue, even.
 
 

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