Why Does My Furnace Keep Turning On & Off?

The average furnace cycles on and off three to six times every hour. When a furnace turns on and off for very short periods of time, it’s called short cycling. Short cycling is a symptom of a larger problem, and if it’s not noticed and then corrected right away, it can cause permanent damage to your furnace, not to mention lead to higher utility bills. Learn more on gas furnace short cycling here.

Common causes of short cycling:

Dirty Air Filter

This is the most common cause and the most easily fixed. Warm air can’t pass through a dirty filter. Since it has nowhere else to go, it backs up within the unit. This sends the incorrect message to your furnace so your furnace shuts off. When your home becomes cold a short time later, your furnace starts up again. To help keep your furnace from constantly turning on and off, make sure that you change the air filter at the start of each new season and check it monthly.

Faulty Thermostat

You should ensure that your thermostat is turned on and set to the “heat” mode before assuming that your furnace needs repairing. It’s also a good idea to test your thermostat to make sure it’s working properly. The placement of your thermostat can make a difference as well. If it’s too close to another heat source, such as direct sunlight or register, it could signal your furnace to turn off.

Corroded flame sensor

The flame sensor is one among the many safety features inside a gas furnace. Burning fuels produce trace amounts of water and whenever water makes contact with most metals they usually rust. The rust accumulates and prevents the flame sensor from working properly. You can clean the sensor yourself, but most furnace repairs involve high voltage and flammable gas, so we recommend that you call a professional.

Improper size

A furnace that’s too big for your home will end up heating it too quickly. When your home is heated too quickly, it also cools too quickly. This can cause the furnace to get stuck in a cycle of quick heating and cooling, which is not energy efficient. It can also shorten the lifespan of your furnace since it is kicking on and off all day long during the cold season. Find out how to estimate which size furnace you need here.

These are the most common causes of short cycling. That’s not to say there couldn’t be another reason your furnace isn’t working properly. Give us a call today. Preventative maintenance on your furnace can help identify problems before they become disasters.

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We have been serving Metro Detroit since 1983. Our goal at Accu-Temp Heating & Cooling is to provide comfort you can feel from a family company you can trust. Give us a call today at 586-598-2828.