My Furnace Keeps Turning On And Off. Should I Be Worried?

Like most homeowners, the only time you'll pay attention to your furnace is when something goes wrong. For instance, you may notice that your furnace keeps turning on and off more often than usual. When your furnace runs for only a brief minute or two before shutting down and restarting a few minutes later, then you're likely dealing with short cycling.

Short cycling places severe wear and tear on your furnace, eventually leading to sudden breakdowns and a shorter service life for your furnace. For your furnace's sake, you'll need to pinpoint the problem as soon as possible.

Why Your Furnace Turns On and Off Constantly

There are plenty of reasons why your furnace may suddenly go on a short-cycling kick:

  • Your furnace air filter is clogged with debris. When the air filter becomes caked with debris, the resulting lack of airflow can cause short cycling.
  • The thermostat is malfunctioning. A thermostat gone bad can also cause your furnace to short cycle.
  • You have a faulty flame sensor. If the flame sensor can't tell when a flame is present in the furnace, the sensor will cause the unit to shut down.
  • You have a faulty furnace blower motor. A malfunctioning blower motor can cause the heat exchanger and the rest of the furnace to overheat repeatedly.
  • Your furnace is too big for your home to handle. A furnace that's too large for your home will be overly responsive to temperature changes, resulting in the furnace kicking on and off repeatedly.

If any of these options seems likely, contact a heating repair service.

What to Do When It Happens

The first thing you should do when your furnace cycles on and off repeatedly is to check your air filter. If you haven't changed it in a while, a fresh replacement will help channel air into the furnace and prevent the unit from overheating and shutting down.

Otherwise, get in touch with your local HVAC specialist and schedule a checkup for your furnace. HVAC technicians are better equipped to go deep inside the furnace to pinpoint and correct the underlying issue behind short cycling.

If your existing furnace is deemed too large for your home, your HVAC specialist may suggest a brand-new replacement that's better suited for your home's heating needs.

How to Prevent It from Happening

Once you've dealt with your furnace's short cycling, chances are you don't want a repeat performance. Here are a few tips that'll help keep short cycling at bay:

  • Keep up with furnace maintenance. An annual inspection will help technicians tackle the beginnings of short cycling before it becomes a serious problem.
  • Double-check your thermostat settings. Make sure those settings aren't being influenced by direct sunlight or external sources of heat such as a portable heater.
  • Right-size your next furnace. Have your HVAC specialist accurately size your next furnace purchase according to your home's heating needs.

The tips here should help with the short cycling problem.