Furnace Keeps Turning On and Off

furnace keeps turning on and off

In the heating realm of the HVAC world, the most common problem we experience is a heater or furnace blowing cool air rather than heated air. But, another common issue is the furnace keeps turning on and off repeatedly. There are a few different reasons why this problem could occur and we will address them here in this post.

Furnace Keeps Turning On and Off….But Why?

Normally, a furnace that is constantly turning on and off in short bursts is operating properly from a safety standpoint. The safety restrictions that are installed on the furnace are probably working as designed and shutting off the furnace to protect the furnace and your dwelling place. There is an exception to this and we will discuss that later.

1)  Dirty/Clogged Air Filter

The #1 cause of a furnace that keeps turning on and off is due to a dirty air filter. This results from a lack of maintenance that is needed for the furnace to run properly and at it’s optimal performance. If the air filter is dirty and/or clogged, then air flow is extremely hindered and thus the heat exchanger cannot cool off. Since the heat that is being produced inside of the furnace is not being removed by cool air, the high limit switch is tripped causing the furnace to shut down.

What to do? Simply check your air filter. If it is dirty or clogged then replace it. Once you replace the air filter, restart your furnace and see if the problem persists. If you aren’t comfortable doing this yourself, call out a local HVAC technician. For them, this is a very common and simple procedure.

2) Thermostat Issue

furnace keeps turning on and off

Another possible culprit can be the thermostat. The thermostat is an electrical component of the heating system and can malfunction like any other electrical device.

What to do? You can troubleshoot a thermostat issue yourself, but it is recommended that a certified technician performs the troubleshooting and repair. The thermostat itself can be taken out of the equation by disconnecting it and  causing the furnace to cycle without the thermostat involved. If the problem persists with the thermostat taken out of the equation, then you will know that the problem lies elsewhere.

3) Furnace Is Too Large (Over-sized)

Rather than the furnace problem being caused by a malfunction, it very well could be due to an over-sized furnace. An over-sized furnace simply means that the furnace being used is a larger unit than is needed to heat the desired space. So, in this case, the furnace will be heating the space to the desired level quickly and then shutting off once it reaches the set temperature. This will cause the furnace to start up and cycle much more often than is optimal for the furnace.

What to do? If your furnace is too big for the space being heated, then the only proper fix would be to buy a new furnace. It would be best to have a HVAC technician come out and determine what size furnace would be suitable for your home or business.

Buying a new furnace can seem expensive at first, but you can probably sell the old furnace if it’s still in good condition. This will help offset the cost of the new furnace.

Related post: What Size AC Unit Do I Need?

Other Causes?

There are other possible causes that can cause a furnace to repeatedly turn on and off in short periods of time, but those listed here are the most common. Some other possibilities (if applicable) would be: a blocked/clogged flue, a dirty flame sensor, or a faulty furnace blower motor (very uncommon).

If your furnace keeps turning on and off and you would like our furnace repair team to come out and troubleshoot and repair the problem, then give us a call at 731-300-1030. Or, you can fill out the Heating Repair Form below and we will get back to you quickly. We, at Cagle Service, serve Jackson TN and the surrounding areas.

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