What to Do when a Furnace Malfunctions

There are many simple steps a home owner can take if their furnace malfunctions. While troubleshooting and repairing complex problems should be left to professionals some furnace problems are easier to fix. Knowing some of the steps you can take to get your furnace working can come in very handy. Furnaces, like many other appliances, are very friendly with "Murphy" and follow his laws. If your furnace malfunctions it probably will do so on one of the coldest days of the year and at midnight, on a weekend, when professionals charge double time.

For your safety, always shut of any gas and electric supplies to your furnace before digging in to any complex repairs. Be sure to save your owner's manual and have it somewhere where you can find it. If your furnace is under warranty be sure not to do anything that will compromise the warranty.

Electrical problems:

Modern gas and electric furnaces should have a shut off switch located in close proximity to the furnace. Before going any further, make sure that the switch has not been accidentally shut off. This has been known to happen. Check your electrical panel or fuse box as well.

Thermostat:

Your next check should be of the thermostat itself. Is your heating system turned on and the temperature set low enough for the furnace to turn on? Thermostats located in small hallways are notorious for being bumped into or accidentally shut off. If you have a mercury based thermostat, the thermostat box itself must be level. If it has been knocked out of level it will not read the temperature correctly and may not turn the furnace on. Check to be sure the contacts inside the thermostat are not dirty. Dirty contacts will not make a connection. Your thermostat should be low voltage, if it is not be very careful to avoid electrocution from it. You can check the voltage from information inside the front cover. If you have a voltmeter you can also check to be sure that the thermostat is receiving voltage. Typically your thermostat should be receiving 24 volts.

Gas:

Simple really, if you have a gas furnace make sure that the main gas valve to your furnace has not been turned off. If you happen to have a gas water heater and it is still operational you will know that you still have gas flow to your home itself. If another gas appliance is not working, you have a problem in your gas main. Call the gas company, do not attempt to repair this yourself. A vent should be located outside your home, for your gas supply itself. This pipe will usually have a screen type cover. Make sure the screen is intact and nothing has built a home inside of it. Blockage of this gas vent can reduce gas flow to your entire home.

　

Pilot lights or igniters:

Make sure your pilot light has not gone out. If it has, follow the steps on your furnace panel or owner's manual to re-light it. If you have an igniter system there are special steps available, both on-line, and in most manuals, for troubleshooting this.

Air flow:

Your furnace must have air flow to work. Check to be sure that your returns and registers are not blocked. Check your furnace filter, it could be completely clogged. If you have too many room registers closed your furnace may shut off due to excess heat build up inside the unit. For gas furnaces you should also check to be sure that the exhaust vent for the furnace is not blocked.

Condensate pump:

If you have a condensate pump attached to your furnace make sure that the reservoir is not full. Most of these units will have a float switch that will turn the furnace off if the reservoir is full.

Blower motors:

Turn your furnace power off before this step! Check to be sure that your blower turns. If it is clogged with dirt or otherwise jammed it will not force heated air through your ducts. Blower motors themselves can wear out. If the motor will not turn, or turns too slowly, you will not get the appropriate heat from your furnace.

Other reasons for malfunctions:

Dirty or defective flame sensors in gas furnaces can cause your system to stop operating. Defective thermocouples are also a common problem. Control boards in furnaces are more complex and require professional troubleshooting.

Troubleshooting charts are available on-line and in most manuals to help you solve simple furnace problems. If you are the least bit unsure of your skills always call for professional service. Hopefully any problems you do encounter will be easily fixed and you can get back to sleep in a warm home.

References:
http://home.howstuffworks.com/home-improvement/heating-and-cooling/how-to-repair-electric-furnaces1.htm
http://home.howstuffworks.com/how-to-repair-gas-furnaces1.htm
http://www.hvac-for-beginners.com/furnace-troubleshooting.html
http://homerepair.about.com/od/heatingcoolingrepair/ss/tstat_furn_coor_4.htm

Author, who's mother inadvertently shut off the power to her furnace and wondered why there was no heat. The author has also been dealing with a cranky furnace for a couple of years themselves.