Furnace Keeps Shutting Off

When your furnace short cycles (i.e. turns on and off too quickly), it does not have time to appropriately heat your home, since it keeps shutting down virtually as soon as it starts. This causes your furnace to overwork, thereby decreasing its lifespan.

The Basic Airflow Process of a Gas Furnace

To be more specific, let’s take a look at how a furnace fundamentally works. In short, air enters your heating system through a return air grille. This return air passes through a filter, which cleans the air before it enters your furnace. Air is then drawn in by a blower section that pushes it through the furnace’s heat exchanger. This is the part of the furnace that actually warms the air as it passes through it. It then warmly flows back into your living spaces, leaving your home feeling nice and cozy.

However, when there is no airflow running through the heat exchanger, the system will overheat and shut off automatically. But it will turn on again as the thermostat automatically calls for heat. This on-and-off cycle will continue until the problem is solved.

Air Filters are the Gatekeepers of Airflow

The first thing you should do to try to solve this problem is to check your furnace’s air filter. Refer to your owner’s manual to find where the filter is located. And be sure to shut off your furnace before you remove the filter. If you find that dirt, lint, hair, and other debris have accumulated on it to the point where the filth seems to have added its own layer of build-up, then this may be the issue. Because airflow is the basis of central heating systems, the obstruction of airflow will cause a system failure.

Cleaning a Reusable Air Filter

Once you’ve located your filter, check to see whether it is disposable or not. A disposable filter will have a cardboard frame, while a reusable one will likely have a plastic frame. If you find that it is indeed reusable, then you simply need to clean it. You can do so by vacuuming it thoroughly. Or you can also take it outside, hose it down, and let it dry completely before inserting it back into the furnace.

Replacing a Disposable Air Filter

On the other hand, if you find that your air filter is disposable, then you’ll need to head to your local hardware store and purchase a new one. Be sure to jot down the size of your filter beforehand. If you can’t decide between purchasing a pleated filter and a smooth one, go with the pleated one, as these have more surface area, which captures more dust and lint.

Keep Track of Air Filter Cleanings/Replacements

A good way to keep your gas furnace working at its best is to keep track of all your air filter changes or cleanings. With reusable filters, you can tape up a lined paper by your furnace. On the paper, you can list the dates of every cleaning. Or with a disposable filter, you can use a marker to jot down the date on the actual filter. This way you can simply refer to the filter and know exactly when it was last replaced.

Furnace Continues to Short Cycle

One last thing you can try if replacing or cleaning the filter doesn’t solve the problem is opening up your registers. Move heavy drapes and furniture away from registers, and do not let these obstructions interfere with the flow of air. If your central heating system is equipped with a zoning system, you can also try opening up the dampers, and allow the air to flow at its maximum capacity.

If none of these troubleshooting techniques work, then you definitely need to contact a contractor, as the problem may be more complicated and requires the attention of a professional. For help finding a qualified furnace specialist in your area, search our contractor listings.