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What to Do with a Heater That Won't Turn Off

Furnaces are meant to turn on and off no more than a few times per hour. If yours starts running, and running, and running without turning off, something is amiss. Don't get too worried—the problem may be rather minor. But you won't know until you follow these steps for dealing with a heating system that won't turn off.

1. Check if the air is warm or cold.

Every few minutes while the furnace is running, check to see if the air from the vents is warm or cold. If the air is always warm, even after the setting on the thermostat has been reached, then the furnace is indeed continuing to run constantly. On the other hand, if the air coming from the vents seems to cycle between hot and cold, you're probably dealing with a fan problem—not a furnace issue. The furnace is turning on and off as it should, but the fan is continuing to run on and on.

2. Check your thermostat setting.

Maybe someone bumped into the thermostat or accidentally changed the setting without realizing. Check to see if the thermostat fan is set to "on" or "auto." It may seem counter-intuitive, but the "on" setting actually tells the fan to keep running constantly, whereas the "auto" function tells it to turn on and off as the heater turns on and off. If the thermostat is turned to "on," turn it to "auto"—chances are, that will solve your problem.

3. Check to see if there is a flame.

If the air coming out of the vents is flowing constantly, but it is not warm, then you may have a problem with the furnace blower. The thermostat never triggers the furnace to turn off because the temperature setting is never reached. Look inside your furnace to see if there is a flame. If there is no flame or the flame is orange, the furnace may not be getting enough gas or the burner may be too dirty to work well. These are both issues that your HVAC (heating, ventilation, and air conditioning) contractor will need to investigate. Depending on the age of your furnace, they may recommend repairs or replacement.

Sometimes when your furnace won't quit, the thermostat setting may be all that's at fault. Other times, more extensive work may be needed. To learn more, contact an HVAC contractor in your area to schedule an inspection.