What It Means When Your Furnace Keeps Turning Off And On

A common issue with heating systems is when the furnace blower turns on only to turn off again quickly without heating your living spaces. Called "short cycling" by heating professionals, this situation can be caused by a number of issues.

1. Malfunctioning thermostat. The most common cause of a short-cycling furnace is a thermostat that's not working properly. When it's functioning correctly, the thermostat senses when your room is getting too cold and sends a message to the furnace to turn on. Then, when the room gets to the ideal temperature, the thermostat tells the furnace to turn off. When it's not working right, the thermostat gives the furnace the wrong information and it turns on and off repeatedly.

2. Dirty furnace filter. Most HVAC professionals recommend that you change your furnace's air filter one a month during the cold weather season. If your furnace is clogged with dirt, heated air can back up into the heating system and send the message for it to turn off. A dirty filter also uses more energy and shortens the lifespan of your heating system. Fortunately, this problem is one of the easiest and least expensive to fix. Most basic furnace filters can be found at the hardware or home improvement store just a few dollars.

3. Bad ignition switch. If you have a newer, high-efficiency furnace, than your heating system uses an ignition switch, rather than a traditional pilot light, to start the furnace. When this switch wears off, it can send a premature message to the furnace to turn on. Then, when the thermostat realizes that the furnace is going and it's already warm enough, it tells the furnace to turn back off, creating a short cycling situation.

4. Less common causes of short cycling. While a thermostat problem, a dirty air filter and a faulty ignition switch are the most common reasons that a furnace will short cycle, they aren't the only potential problems. A bird or other object lodged in the chimney or flue can cause this to happen, as can a corroded flame sensor.

Short cycling is a problem you want to take care of quickly. Not only does this situation affect the efficiency of your heating system and the heat in your living spaces, but short cycling puts a lot of stress on your furnace and uses unnecessary energy with all that starting and stopping. If your furnace is turning on and off repeatedly, it's time to call a local heating contractor, like Clay's Climate Control LLC.


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