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Furnace Short Cycling: How to Fix a Furnace That Won’t Stay On

furnace short cycling

The furnace clicks but doesn’t turn on. Even when you play with the thermostat, the furnace won’t kick on. When it does turn on, it won’t stay running very long, usually only a minute or less. What’s going on?

These conditions can be caused by what is known in the HVAC industry as “short cycling”. The furnace turns on and off in quick bursts, often leaving you cold and frustrated. Let’s look at four causes for this condition and what you should do.

Your Air Filter Is Clogged

One reason why your furnace may be turning off is that it became too hot. This is a safety feature to ensure the unit doesn’t overheat. A common reason for overheating is a clogged air filter. Cool, clean air coming into the furnace helps keep the unit from overheating.

A clogged air filter acts as a barrier to the cool air, which causes the unit to work harder and get hotter faster. When the furnace reaches a certain temperature, it cuts off to allow it to cool down. Once it drops a few degrees, it starts back up and gets overheated quickly, shutting off again. This happens over and over.

Check the air filter. If it’s clogged, replace it. Then turn the furnace on again and see if the short cycling has stopped.

Your Thermostat Needs New Batteries

Thermostats are the brains that tell the furnace to turn on and off when the house reaches preset temperatures. Check the thermostat’s batteries. If they are low on power, it can cause trouble with the signaling to the furnace. Change them and see if that fixes the short cycling.

Your Furnace Blower isn’t Working

This is an uncommon reason for when furnace clicks but doesn’t turn on, but it does happen. When you hear the furnace turn on, put your hand in front of the vent. If you don’t feel any heat coming out, you may have a blown furnace blower. The only option is to call for a technician to come out and check the system.

Your Furnace isn’t Properly Sized

An oversized furnace puts out more heat faster than the house requires. So, it doesn’t need to work very long to get the house warm. It turns on for a minute or two and then shuts off because it’s not needed.

If you just had a furnace installed or bought a home with an existing furnace, you may have an oversized unit. You need to talk with a furnace specialist to talk about your options.

What to Do If You Can’t Stop the Short Cycling

If you cannot stop the furnace’s short cycling with the methods outlined above or the furnace won’t kick on at all, it’s time to call in an expert. Contact Stan’s Heating and Cooling today. We offer 24/7 service on all furnace brands.