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View Full Version : Gas furnace fan turns on but nothing comes out


sheldun
Oct 15, 2006, 11:33 AM
When I turn on my gas furnace, the pilot light comes on, but goes off afer a couple of minutes after having produced nothing. When I turn on the manual fan, it starts up, but no air comes out. Any ideas?
Thanks

labman
Oct 15, 2006, 04:39 PM
There is a sensor that tells the control board the pilot is on. The sensor could be bad, or the board may not power the gas valve, or the gas valve could be bad. It is a matter of finding the components, a place to check for voltage, and following the sequence.

To do simple checks like this you do need some tools. A test light, a meter, or a voltage detector might be the best place to start with. I came across the niftiest gadget for trouble shooting, a voltage detector. They work through the insulation of wires. There are several brands. I have a GB Instruments GVD-505A, less than $15 at Home Depot. Touch it to a hot wire, and the end glows red. Find the doodad that lights it on one side, and not the other, and you have the culprit. You do not have to open up housings and expose electrical contacts. You are looking at where your hand is, not where the meter is. Most people are capable of doing repairs and will get it going and not get hurt if they use a little sense. The voltage detector makes it even easier.