My furnace is blowing out cold air some of the time. I went down and took off the panel and turned the power switch off, then back on. It goes through the normal sequence to light the burners: The fan kicks on then the igniter switch heats up, it makes some clicks, then the burners come on. As soon as the igniter switch starts to cool off, or dim down the burners turn off. It repeats that process three times, fairly quickly, then it just shuts off-leaving the fan on, thus the cold air. From what I have read, these sounds like it could be a number of things, but if anyone knows what I should replace, or check first, or has any input at all, it would be greatly appreciated. Thank you.

Jessie

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Originally Posted by johnston2008

My furnace is blowing out cold air some of the time. I went down and took off the panel and turned the power switch off, then back on. It goes through the normal sequence to light the burners: The fan kicks on then the igniter switch heats up, it makes some clicks, then the burners come on. As soon as the igniter switch starts to cool off, or dim down the burners turn off. It repeats that process three times, fairly quickly, then it just shuts off-leaving the fan on, thus the cold air. From what I have read, these sounds like it could be a number of things, but if anyone knows what I should replace, or check first, or has any input at all, it would be greatly appreciated. Thank you.

Jessie

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I forgot to add that it is blowing warm air some of the time, otherwise it would be exemely cold in my house.

It sounds like your flame sensor is dirty. Depending on what type of furnace you have you should be able to get a diagnostic code from the main control board. A chart on the front of the burner panel or backside of panel will indicate an ignition failure. It could be other things but try to get the error code. Some times furnaces have a small viewing window on the panel to let you count flashes from the board. If the control board is located in the blower section of the furnace you need to do it with the door on otherwise the door interlock will turn power of to the furnace and rest the control. Get the code first and then if your code legend is on the backside of that door you can figure ot the code. Flame sensor are usually easy to clean with some steel wool.(no soap of coarse). The flame sensor ensures ignition has occurred as you do not want raw gas entering your funace for more than several seconds. The flame sensor looks like a small wire a little less diameter than a coat hanger. They vary in location and style depending on which furnace you have. I have diagnosed and solved this problem over the phone with friends. You can't really blow anything up because this safety will not allow the burner to ignite for long if something is wrong and they are usually so simple to get at it is hardly worth a service call when I am really busy. That is about the only thing I would recommend someone that is not trained try to fix. Hope this helps.

Thank you very much. I see what I can find down there tomorrow.