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snurb 01-11-2009 12:02 AM

Furnace burners flame out after a few seconds
Here is the problem with my furnace. The thermostat will call for heat, the inducer will start and shortly thereafter the burners will light. If left alone, the burners will stay lit for about two or three seconds and then shut off. The furnace will then cycle through these processes a few more times before shutting down completely.

After reading some earlier posts I decided to remove the upper access panel and have a look inside. By accident, I made the following discovery. If I manually fan extra air into the burners while the inducer fan is running the burners will stay lit. Fan them until the main squirrel cage fires up and the furnace will continue to burn until the temperature originally called by the thermostat is reached. The furnace will then shut off normally until the thermostat again calls for heat.

Heat sensor, clogged flue, or something else? Any and all help will be appreciated.

biggles 01-11-2009 09:03 AM

if it is consistantly doing that same cycle .....burner on then off sounds like the DWYER pressure switch that senses the air the induced draft motor produces.when your stat calls for heat that ID is the first thing to run on your pressurizes the tube from the housing of the air ...closes (2 wires on it) and the heating cycle starts.....spark ignition...main the sta calling for HEAT pull the tube off the DWYER with the ID fan running check,and try to hear a single click sound put it back on to hear another click again(burner might/might not come on).the air going into the tube is proofing to the DWYER that the ID is running and sending air into the burner chamber.if it is adjustable give it a couple of 1/4 CCW turns(note the original position) with the ID running it should make the burner........check that hose for cracks should slip on tight to the control,and the sensing tube on the air duct for the ID.if you get the burner running after this :thumbup:to check it the other way pull the tube OFF the DWYER the burner ONLY should shut off.....main furnace fan will stay on along with that ID motor.
and ID will also stay on

yuri 01-11-2009 09:10 AM

You got a potentially VERY dangerous situation if you have to add air to those burners. You may have a partially plugged heat exchanger, slow moving ventor fan which will cause poor combustion/CO production and possible poisioning etc etc. That pressure switch proves adequate draft thru the heat exchanger and proper air for proper combustion and is not to be fooled around with/taken lightly l. I would recommend you get 2 good CO detectors and a Pro to check that unit unless you like living dangerously. Saving a few $$ ain't worth risking your families safety. I write this way for ALL the people reading these posts. Have seen a severe CO incident and 2 of them are in a permanent coma.

metx 01-13-2009 07:58 AM

on your flut (bottom) you should a small switch with 2 wires .that is called a spill switch .if co2 backs up it shuts the gas valve .meaning co2 .need the flut clean or chimney cleaned .I just did a job with the same problem and it was a dead bird .There is a way to check to see if it is that .

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