With proper furnace maintenance and occasional tune-ups, furnaces usually have a long and dependable life. And while things can go wrong, most can be fixed.
By the time a furnace needs to be replaced, high-efficiency improvements have been made in newer systems, and reduced utility costs will at least partially offset the cost of a new furnace. There are several signs that a furnace needs repair.
The pilot light should burn with a blue flame. If the flame is yellow or orange, there may be a carbon monoxide problem. Turn off your furnace and call a service technician. Carbon monoxide in your home can cause serious health issues, so don’t delay in getting the problem repaired. If the pilot light flame is burning blue but flickering, that could be a different problem. Most likely, the gas supply line is partially clogged and needs to be cleaned.
The heat exchanger is the part of a furnace that separates the air that a furnace circulates throughout a home from the hazardous gases in the air that have been heated in the combustion assembly. The air you breathe moves through tubes that pass through the combustion chamber. The harmful gases get exhausted from the chimney or vent, and the clean, heated air circulates around the home.
The most common problem with the heat exchanger is that after repeated expanding and contracting from heating and cooling, metal fatigue causes cracks or holes in the tubes. That allows the dangerous gases to mix with the warm air that circulates in the home. A service technician can check your furnace for a cracked heat exchanger.
If the thermostat display is blank, check the batteries. If replacing batteries does not solve the problem, check the breaker box. If the breaker is not thrown, it may be time for a thermostat replacement. If the furnace is running continuously and not shutting off, try setting it to auto and then try it at different temperature settings. If it still runs continuously, the thermostat may need to be replaced.
The limit switch senses the temperature of the furnace and turns the furnace off and on during the normal heating cycle. It is usually very dependable, but occasionally it fails and will prevent the furnace and blower to turn off or on. The limit switch also has a high temperature limit that will shut off the heating burners and leave the blower working so that the heat exchanger does not overheat. Replacing the limit switch is a relatively inexpensive operation.
Different noises indicate different types of problems with your furnace, and most of them need attention. A squealing noise is likely to be caused by a fan belt problem. There is an electric motor in a furnace that uses a fan belt to turn a fan that blows warm air through ductwork and into your home. If the belt is worn and damaged, it may slip and make a squealing noise. Turn off your furnace and have the belt replaced. A scraping sound is probably the result of worn bearings somewhere in the power assembly. Turn off your furnace and get the problem fixed to avoid additional damage.
Do you hear bangs and clangs in your ductwork when your furnace starts up and the warm air starts blowing? That is the result of cold ductwork expanding from the heat, not an operational problem that will cause damage. You may want to make sure the ducts and joints are adequately attached and secured.
If the amount of warm air is reduced, check to see if the air filter is dirty or clogged. Change the filter often. If clean air cannot get in the cold air vents and through the filter, warm air will not come out. If the full heating flame is burning and no warm air is moving through the ducts, there is a circulation fan problem. The cause is most likely a worn-out or broken fan belt. The motor and fan itself have other moving parts that can fail.
Some furnace problems are more urgent than others. Some problems are dangerous to the health of homeowners, and others need attention to avoid additional harm. All furnace problems need attention to keep your home comfortable and safe.
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