Why Is My Furnace Short Cycling?

a living room with a fireplace

Your home’s furnace is your best friend when it comes to getting you through those wicked winter months, but what do you do when the heat just suddenly stops after being triggered on? This is referred to as short cycling, and it could be a more serious problem that a homeowner needs to address to make sure a heating system is back up to code. Here are some things to consider if you notice that you’re not getting the airflow you need, or that too much power is being expended by your heater for little output.

It could be time to replace the air filter.


If you find that you’re dealing with furnace short cycling, one of the common causes of this issue is actually a dirty air filter. That’s because that dirty air filter is actually causing a great deal of resistance, blocking airflow because of all of the dust and allergens plugging it up. This makes the furnace work that much harder, which can lead to overheating and significant damage to the system in the long run.

Cleaning air filters is part of routine furnace maintenance and should be changed out prior to those awful winter months, or after depending on the situation with your home’s heating system. If it’s part of an HVAC unit used for air conditioning in the summer, it will require both a spring and fall cleaning. Cleaning out a clogged air filter will also put less pressure on a heater, avoiding a higher energy bill while addressing the short cycle problem.

The capacitor may be failing.


If you’re using a heat pump to keep your home warm through the winter, then you have capacitors that help keep it running. These are also referred to as the start and run capacitors. The start capacitor gives the system a little bit of a boost when you start the heater up to help get it going. Meanwhile, the run capacitor maintains a steady electrical current to make sure the heat pump continues to run properly. If your system has a fault with either of these, it can account for short cycling.

This is a significant issue for a furnace system and requires the assistance of a licensed technician to replace the run capacitor and keep the heat flowing throughout your household. Heat pumps are revered for their efficiency, so starting and stopping constantly makes any kind of energy savings null and void. In addition, the constant short cycling will devastate the life span of the heat pump, leading to another costly expense in having to replace a specific model for your household.

You could have a refrigerant leak.


One big problem that is associated with the short cycling of furnaces is if the unit is leaking refrigerant. Refrigerant removes heat from the air outside to warm your home with that heat through the transfer power of a heat pump. If there’s a leak, the system is going to overwork, sending your heating bills soaring without much in the way of results in keeping the home warm through the normal cycles.

An overheating and short cycling issue can arise, even causing an outdoor unit to develop ice on the coil, clogging ventilation and making proper airflow next to impossible. Removing this clog should not be left to a DIYer. Call in a licensed professional to address this situation, as working with refrigerant requires training, proper equipment, and certification to make sure the obstruction and the leak are handled. This could also uncover a significant crack that could require replacement, so be sure to call a technician today if you notice this issue.