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6 Reasons Your Furnace Is Running Constantly

6 Reasons Your Furnace Is Running Constantly

A furnace that runs constantly is not only annoying to listen to but also wears down the system and increases your monthly energy bill. Thankfully, the possible causes are easy to spot and don’t take long to fix. Take a look at our guide below.

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Why Is My Furnace Operating Constantly?

1. Dirty Furnace Filter


A dirty furnace filter is the top reason for a constantly running furnace. The filter collects dust and debris that restricts airflow and causes overheating. When the system overheats, the fan stays on to play catch up on cooling it down.


We recommend replacing your air filter every one to three months to ensure proper airflow.

2. The Fan Is On


If you select the “on” mode for your furnace’s fan, the blower will keep running.


This problem has a simple fix. Either turn the fan to “off” mode, or set it to “auto” so it only runs when the furnace is turned on.

3. Temperature Is Set to a High Limit

The furnace will run until your home’s internal temperature reaches the temperature to which you set your thermostat. If you set the temperature too high, the furnace will run constantly trying to reach the set temperature.


Bump the temperature down a few degrees to put less strain on the system.

How to Inspect & Replace the Thermocouple in Your Furnace

4. Furnace Is Not Derated


Derating your furnace is the process of limiting the amount of gas that reaches the burner. This prevents the furnace from overheating. A furnace that isn’t derated may overheat, causing the fan to run constantly.


Give us a call, and we will have one of our highly trained technicians come out to rectify this for you.

5. Blower Issues


Your blower is probably the cause of a constantly running furnace if the system is turned on but doesn’t produce any warm air. Corroded wires or a blown fuse can cause this issue.


Since this problem involves electrical components, contact a technician to fix the problem safely.

6. Malfunctioning Pilot Light

A malfunctioning pilot light—which lights the gas before it reaches the burner—will cause your furnace to run constantly because the system can’t reach the set temperature without an adequate supply of gas to warm the air.


While at one time homeowners had to light a match to fix this problem, most pilot lights now can be reset with the press of a button.

Typical Run Time for a Furnace

Typically, a furnace will run two to three cycles per hour, and each cycle will run between ten and fifteen minutes. This cycle time may increase slightly in extreme cold weather.

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Furnace Repair & Replacement Services By Horizon

Our team of technicians offer reliable furnace repair and furnace replacement services for homes in your local area. By offering same-day service, next-day installation, and 24/7 emergency services, we’ve got your back whenever you find yourself in a pinch. Our staff provides comprehensive heating repair services in Raleigh, NC and other areas.

Our professionals also offer other types of HVAC solutions such as boiler repair, heat pump replacement, and whole-home humidifier installation. Our team of technicians guarantees to get the job done quickly and efficiently every time. Give our team a call by phone at 1-800-642-4419 to schedule an appointment today and achieve whole-home comfort for the whole family.


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