Troubleshooting A Gas Furnace That Won't Ignite

Few things could be as frightening as switching on your furnace on the first cold day of fall--only to find that it won't produce any heat. Before you reach for the phone to call a professional furnace repair person, however, be aware that the problem may be simple enough to solve on your own. This article will walk you through the process of troubleshooting a gas furnace that won't ignite.

The Root Of The Problem

Most ignition problems with gas furnaces involve the pilot light. Just as with a gas stove, the pilot light's responsibility is to stay lit at all times, thus providing the ignition necessary for combustion to happen when the furnace kicks on. When the pilot light goes out, the furnace will no longer work--even if everything else is functioning the way that it should.

Thus the first step in troubleshooting a non-igniting furnace is to check that the pilot light is lit. You may accomplish this by removing the cover plate situated below the gas control knob. If the pilot light is lit, your problem is more complex, and will likely involve the intervention of a trained professional.

Relighting The Pilot

If, on the other hand, you are unable to see the pilot light, you may be able to get your system back on line simply by relighting it with a long stemmed lighter. Before you attempt to do this, however, be sure to switch the gas valve to its off position. Allow several minutes for any lingering gas fumes to dissipate. Now use your lighter to apply a flame to the pilot orifice, while rotating the gas valve to the pilot position.

Pilot Won't Light

If you're unable to get the pilot lit in this manner, there are two possible problems. The first is that the tip of the pilot orifice has become clogged with debris. Try cleaning it out using a thin metal wire (paperclips work great), and then try to light the pilot again.

If the pilot still won't light, it may be the case that your gas valve is closed, thus preventing gas from flowing to all parts of the furnace--including the pilot. Check that the valve is not only open, but also properly adjusted.

Pilot Lights But Won't Stay Lit

If you are able get the pilot lit, only to have it go out again, the problem may have to do with the pilot adjustment screw. This screw is used to fine tune the amount of gas flowing into the pilot tube. Consult your furnace's manual to determine where the adjustment screw is located. Adjust it until you are left with a flame between 1.5 and 2 inches high. A flame of this size should stay lit without any further problems.

To learn more, contact a heating service company like Air Doctor Heating and Air Conditioning Specialists.