5 Reasons Why Your Furnace Keeps Running

Your furnace should turn itself on and off every 10-15 minute cycle. If it’s running constantly, then your furnace has a problem.

Your furnace likely keeps running because of:

  • faulty limit switch
  • wrong thermostat settings
  • dirty furnace filter
  • blower fan is malfunctioning
  • your pilot light is out

Below you’ll find out how to fix all of these issues and get your furnace running normally again.

Let’s get started.

5 Reasons Why Your Furnace Keeps Running

1. Faulty Limit Switch

The fan limit switch is responsible for turning the blower motor on once your furnace reaches your preferred temperature.

If your furnace switch is faulty, then it won’t be able to regulate the temperature alongside the thermostat.

This can be dangerous as your furnace may overheat, causing damage to the internal components of your furnace.

If you suspect your limit switch is to blame, you should stop using your furnace and get it replaced.

2. Thermostat Settings are Wrong

If you set your thermostat at a high temperature, your thermostat will need to continuously work to hit the desired temperature.

If you put your thermostat on “On” and not “Auto” this will tell your furnace to continue running without cycling.

To fix this problem, set your thermostat to “Auto” and put it at a reasonable temperature.

It may be that your thermostat wiring is also wired incorrectly which would need to be diagnosed by an HVAC technician.

3.Dirty Air Filter

If you have a dirty furnace filter, your furnace will struggle to send the hot air to the rooms in your home.

It’s also possible that you have installed your air filter backward, which can also impede the airflow from your furnace fan.

The best way to fix this is to replace your filter and ensure it’s installed in the proper direction.

4. Blower Fan is Running

If your furnace is running constantly but you only feel cold air coming from your vents, this is a sign that you have a problem with your blower.

If your blower motor is malfunctioning, it’ll continue to blow air even when your furnace isn’t running.

A sign that your blower motor is running constantly is higher energy bills than normal.

To fix a running blower fan, it’s best to hire an HVAC professional who can help troubleshoot the problem.

5. Pilot Light Malfunctioning

If your pilot light goes out, your furnace may run indefinitely and only blow cold air.

To fix a malfunctioning pilot light, try to reignite it first to see if that helps.

You can even try resetting your furnace. Depending on which type of furnace you have, you’ll have to reset it in a different way.

Is it Normal For a Furnace to Keep Running?

A furnace running constantly is not normal.

You may however be in a scenario where the outside air temperature is so low that your furnace needs to run more than usual to heat up your home.

If however the temperature outside is normal for winter but your furnace never shuts off, then you have a problem.

It’s best to have it fixed right away as overheating can cause damage to your furnace and home.

When to Call an HVAC Professional?

No matter if you’re dealing with a cracked heat exchanger, air conditioning or faulty HVAC system, you should call an HVAC professional.

Doing repairs yourself if you don’t know what you’re doing can cause more harm than good.

About Roy Cohen

Roy Cohen has a burning passion for heating, cooling, and ventilation. He aims to help you save money on expensive repairs and bring you the best HVAC products. He has years of experience behind him in HVAC repair and garage maintenance.

You can find Roy at his LinkedIn or his email: [email protected]

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