How to Tell if Your Furnace is Short-Cycling & What to Do

broken home heating system

Winter is just around the corner. There is a chill in the air, and soon, you’ll feel the temperatures drop even more. Homeowners can keep their household warm and comfortable throughout the cold season by ensuring that your furnace is in excellent working condition. You should fix any issues it has immediately. One issue that homeowners notice is that their heating system is short-cycling. This is when your furnace runs then shuts off and starts again repetitively. When this problem occurs, it is best to have a professional handle the situation.

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Is My Furnace Short Cycling?

A furnace works by running continuously until the set temperature is reached. After that, it will turn off and let the area maintain the same heat level. It will take some time before the unit needs to restart because of dropping temperatures.

On the other hand, when your furnace short cycles, it will switch on and shut off in quick succession. The desired temperature is not achieved when this happens. When the furnace turns on and off repeatedly, it will wear out the system. Not only that, but the house will still feel cold and uncomfortable even though the furnace is running.

What Causes A Short Cycling Furnace?

why does a furnace short cycleShort cycling should be repaired immediately. It renders your system inefficient. It also results in wear and tear. You and your family are also left in the cold. Various things cause this problem, and the repair will depend on your specific situation. Below are some of the causes of short cycling:

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1. Overheating Furnace

A furnace heats your home and, in doing so, the unit can get too hot. An overheating furnace is usually caused by blocked vents and clogged air filters. Fortunately, heating and cooling systems have built-in protection. When the heat reaches a dangerous temperature, the system switches itself off immediately. This emergency step ensures that your system does not incur damages, such as a cracked heat exchanger. Carbon monoxide can leak from these cracks, which can be fatal if you do not remedy the problem quickly.

2. Bad Furnace Flame Sensor

furnace burner

A bad flame sensor means that the flame will go out as soon as it lights. The sensor is responsible for monitoring the gas valve. It is a safety measure that keeps raw gas from being distributed throughout your home. It shuts the valve off when no flame is detected. Unfortunately, a faulty sensor will switch off the gas valve even when it is needed. The sensor might just need cleaning or a replacement. Call an HVAC professional.

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3. Blocked Heat Grates

The warm air is pushed out of the heat grates. If these heat grates are blocked, the heat will be trapped in the furnace and result in overheating. Your furnace will short cycle unless the problem is fixed. Keep in mind that grates are controlled by dampers, which you can open or close to assign which rooms in your home get heated. This helps increase your home’s energy efficiency. However, make sure that at least 75 percent or more of the grates are open at all times. Otherwise, your furnace might overheat.

4. Clogged Furnace Filter

changing the furnace filter

A dirty HVAC air filter will let your furnace operate for a little while before turning off. It will also result in your furnace pumping out air that is hotter than usual. A clogged air filter will also restrict the airflow. When air does not flow back to cool down the furnace, it will overheat and then shut down. To prevent these issues from happening, replace or clean the filter when necessary.

5. Blocked Exhaust Vents

Exhaust vents should be open at all times. Unfortunately, snow, beehives, plants, and nests, among other things, can block the vents. Visually check the vents regularly and remove all blockages immediately. If a wild animal is blocking the opening, contact your local animal control to avoid exposing yourself to harm.

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6. Wrong Thermostat Location

malfunctioning thermostat

The thermostat is equipped with sensors that measure your home’s indoor temperature. This way, your furnace can respond when the temperature drops below the temperature setting. However, this feature will not work correctly if the thermostat is placed on the wrong spot. Avoid placing the thermostat near heat sources, such as a sunny window and a heating grate. Otherwise, the thermostat will think that your house is already warm enough and signal the system to shut down. Make sure that the thermostat is located away from anything that could influence its temperature sensors.

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7. Furnace Is Too Large

You might think that having a large furnace means it can keep your home warm longer and better. However, this is not the case. A bigger furnace does not always mean it is the best option. Excess capacity can lead to short cycling. Thus, its parts will wear out faster, you will experience more temperature swings around the house, and your home’s cost-effectiveness will decrease. The only solution, in this case, is an expensive one. You’ll need to purchase a new unit that is the correct size for your home. Contact your local HVAC technician to conduct a Manual J load calculation so you can find the best furnace for your home.


Make sure your furnace is in tiptop shape before winter. If your heating system is short cycling, find the cause of the problem. Use the clues above to help you. Reach out to a professional HVAC contractor to conduct a proper check-up. This way, all issues are fixed, and you can enjoy a warm and comfortable winter.

Contact Point Bay Fuel For All Of Your HVAC Needs


Point Bay Fuel provides excellent HVAC services in Monmouth and Ocean County, New Jersey. We have highly-trained, certified technicians who offer top-notch heating and cooling services, such as furnace repairs, A/C installations, and more. All our experienced techs have the right tools, skills, and knowledge to correctly service any HVAC make and model.

Our company has one of the most affordable service costs in the area. Our HVAC services help increase your home comfort, energy-efficiency, and cost-effectiveness. If you need to replace your HVAC system, we can help you find the best one that fits within your budget. Your satisfaction is our priority so all of our services come with a guarantee. Book an appointment and call Point Bay Fuel today for a free, no-obligation, in-home estimate.

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