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Honeywell Gas Furnace

The furnace will turn on, the burner will light and then turn off 5-10 seconds later. It will do this three or four times and then shut down. If I go to the thermostat (it's an old style manual) turn it down then back up it will work properly only for that cycle. Once it shuts down after reaching temp. it goes back to not functioning properly again

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  • Jay15 Nov 20, 2007

    The Model is a Lennox M 24 Elite series. blew all the debris out of the flame channels checked the flame sensor. seems to work better but still malfunctions the odd time

  • Jay15 Nov 20, 2007

    the diagnostic flash code indicates that everything is working properly, checked that first of all. could it still be the flame sensor not working as it should? I replaced the thermostat to a programable digital as I intended to in the first place (it's a Honeywell).

  • pie5 Jul 14, 2008

    Have a Lennox M24 gas furnace. Switching on the thermostat results in burner flames firing but for short period only (approx 1-2 mins) then ceasing while fan (i assume that) continues to operate. When flames are burning diagnostic ligt blinks steady. When they stop, LED flashes 4 times -diagnostoc mentions flame rollout switch. Can I assume that if burners do light if only for short period that electronic ingnition system is fully OK. Why might the buners be stopping. Have tried resetting by switching off funace and thermostat and re-starting but burners still shut off as above.



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A Make and Model number of the furnace not the thermostat will help but I can walk you thru the operation of a typical furnace. It sounds to me that the burners are igniting properly but the flame sensor is not sensing the flame and shutting down the system. You will need to find the sensor and clean it and check the wire from it to the control board. Typically, the flame sensor is found at one side or the other of the burner box. It is a small probe that the flame hits. Depending upon your model it may have a small wire attached to it leading back to the control. Or it may be part of your auto-pilot assembly. ? At any rate, you will need to get to it and very delicately brush it off. Then inspect the flame channel. This is a trough area where the flame travels to ignite all burners. Over time, they tend to fill with rust and debris. Take a small screwdriver and run the blade down the trough. Inspect the wire that goes from the flame sensor to the control board. Make sure it is not frayed or broken or shorting out and that the connection at the board is good.

Beyond that, it's time for a technician to come.

Let us know the Make and Model of the furnace (found inside the furnace cabinet) and maybe we can help you further.

Posted on Nov 20, 2007

  • Chandler Ede
    Chandler Ede Nov 20, 2007

    If it is now intermittant, you may be looking at replacing the control board $$$$ on a Lennox. Get a technician in and have him check your gas pressure. The lennox will also have a diagnostic code flashing on the control board after three attempts. On the back of the access pannel you will find a chart indicating what the flashing coorispons to.

    Good Luck!

  • Chandler Ede
    Chandler Ede Nov 20, 2007

    I would hate to steer you into buying a new control board, you can start with a new sensor and see if it takes the problem away.



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