I am a furnace technician and to solve the problem.You will find on the opposite side of the ignitor their is a flame rod with a wire connected to it.Remove it and clean it with sandpaper and re install it and it should fix the problem.If this is dirty it won't sense ignition and the board thinks that is it introducing raw gas into furnace and it isn't igniting and shuts off as a safety precaution.If you see a blueish tinge on the flame rod you should probably replace it.
Check the flu. It has an outer pipe for fresh intake air and an inner pipe that allows the cumbusted air vent out. If the inner pipe is rusted through it sucks the combusted gas back into the fresh air side and flame dies off due to the lack of oxygen and shuts off the gas valve.
Gas direct vent units such as these (not sure what model you have) typically have a thermocouple, or if the thermostat is mounted away from the unit, a thermopile. Either of these could be defective or in some cases, the valve is bad. Make sure there is no obstruction at the vent outside as well, as this will cause the unit to shut off due to lack of combustion air.
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I take you mean there is a fan coming on that blows AC air thru the vents and is the same fan used to blow the heat ? If that is the case is the fan coming on when the heat comes on ? If not then that is why you are not getting the heat. That can be from a temp sensor not working or a control board or a contactor First see if the fan even comes on or if the same fan is used for both AC and heat
two things the pressure switch not working or the fan control afc not working could need cleaning at the back of the afc try this the afc works on temp rise to bring on the fan afc temp fall to shut of fan so it sound like the afc is not coming on at temp rise, also check if air filter is clean
The problem is withthe venting. Your vent pipe goes out of the house in such a way as to catch the air when it is windy and cause the pressure switch to cut out. The flame may only run for a short time, then shut down and then restart. The heat exchanger never gets hot enough to give you warm air.
Check where the vent pipes exit the house. Try adding on an elbow and turning it so that the wind cannot blow back the pipe. Turning it down towards the ground often is good. Make sure that the exhaust cannot recirculate back to the intake pipe also.
Also check that there is no water build up hanging in a pool where the vent pipe may have sagged a bit. this will make the pressure switch much more sensitive.
I hope that this will help you to solve your problem!
This is a little complicated because it can be several things and you need to provide more specific info....It could be your furnace is shutting off on the High Limit...which means your furnace is running too hot...check the filter , return air vents etc would be an airflow problem...dirty blower....Furnace can be too big for your house....when the furnace shuts off on High LImit , the fan will continue to blow air , cooling it down as usual and once the furnace cools enough to reset the high limit trhe furnace will Ignite again as long as the thermostat is still calling for heat . The furnace could also be running too long and getting too hot....your Ductwork can be too small...many factors come into play
you might want to check the filter, if the filter is restricting the airflow the furnace will over heat and it will shut down. if you turn it off and on it will reset it and it will try again. Pull the filter out half way and try that, if it runs fine then clean the filter or get a less restrictive one.
Is this furnace standing pilot or electronic? if standing pilot turn power off then take t-stat off wall and connect the wires labeled r and c together and see if that keeps furnace working. If electronic check flame sensor you can check flame sensor buy cleaning with steel wool. if that doesn't work then try t-sat.
first off buy yourself a honeywell stat, in my personal opinion lux stats are garbage, I have run into so many that are bad stats !!! but as far as your fan not shuting down, sounds to me like your fan center on your circuit board is bad and will not shut down the fan when needed, you will have to replace the circuit board, as the fan center is a part of the whole of the circuit board, hope that helps