A Short Cycling Furnace: Why is it Happening? Knowing the root of these causes can aid you in diagnosing this problem and finding the appropriate solution.

1. Thermostat Issues

The most common source of a furnace that frequently cycles is an issue with the unit’s thermostat. Perhaps the most common cause of furnace short cycling is a thermostat in some state, whether it be that it’s malfunctioning, improperly calibrated, or placed where it doesn’t represent room temp exactly.

For example, if you have the thermostat sitting near an element that is giving off heat (such as a lamp) or it’s in direct light and those new lights just happen to be kicking out some added warmth too, the thermometer might signal to your furnace far sooner than needed because it thinks what felt like 65°F on Friday now must feel quite different—it was telling itself.

Solution: Make sure the thermostat is central and not near any heat sources. Invest in a programmable thermostat as well, especially if your current one is old or not functioning correctly.

2. Clogged Air Filters

Over time, dirty or clogged air filters can suffocate your furnace and cause it to overheat. The furnace automatically turns off when it becomes too hot to avoid permanent damage and then back on again once sufficiently cool. This process repeats itself and short cycling occurs.

Solution: Change your air filters frequently. Tempasure recommends changing your air filter every 1-3 months based on usage and the type of allergen-free filters you use. Regularly cleaning your air filters will ensure that you have the proper airflow, which in turn would help to prevent overheating.

3. Oversized Furnace:

Short Cycling due to the Size of Furnace—An oversized furnace can be a common reason for short cycling. When you have a large furnace, it will warm up your home fast and stop the system because the thermostat tells it so. But rapid heating with a quick shutdown results in short cycles.

Solution: If you think your furnace is oversized for the space it serves, contact an HVAC professional to determine whether to replace or adjust any forced-air heating system. You need registered furnace experts to determine your heating needs and the ideal size of the furnace. There may be instances where the furnace cannot accommodate an adequate size of this unit and thus must be replaced with a new model.