On Again, Off Again: A Short Cycling Furnace

HVAC systems are designed to shut off when something isn’t right. This keeps you safe. When shutdown happen several times in an hour, it’s called short cycling. Your furnace wants to do its job but keeps running into the same system failure. Short cycling is extremely hard on your furnace and will raise the host of your hearing bill. Therefore, this is something that can’t be ignored and must be addressed right away. Some solutions can be resolved quickly and easily by the homeowner. Other times, it’s a symptom of a larger problem that will likely require a certified technician. Read on to learn more about short cycling, what quick fixes can you can check yourself, and when you should call Owens for help.

First, the following are common causes for a short cycle that can be easy fixes for any homeowner:

Check the air filter — Luckily, this is the most common cause and the easiest to fix. Air cannot easily pass through a filter that is past its useful life. When this happens, hot air will build up inside the system. Before long, the system recognizes that something isn’t right and shuts itself off. The system will kick back on after a few minutes once things have cooled down, thus causing a short cycle. To rectify this issue, simply inspect your filters regularly and replace when it appears to be dirty. The pollens in the fall air can quickly build up. Therefore, it’s a good habit to put a new filter in before the start of each heating season.

Check the thermostat — Replacing a thermostat is much easier and less costly than major repairs to your furnace. That’s why checking your thermostat is a great idea. First, make sure the temperature settings are properly configured and that the unit is set to ‘heat’ mode. If that doesn’t work, see our blog post on “How to Test if a Thermostat is Properly Functioning.” It’s also possible that the thermostat simply thinks the house is properly heated and is telling the furnace to shut off. This can happen if the thermostat is too close to an air vent or is in direct sunlight. This is mostly likely to happen if you recently moved your thermostat is too close to an air vent or is in direct sunlight. This is most likely to happen if you recently moved your thermostat or installed a new system. If your thermostat says it’s much warmed in your house than it actually is, then this might be the problem.

If you are able to determine that the issue is not caused by the reasons above, it’s important to your safety that you involve a certified technician. Don’t worry, Owens will make the process as painless as possible.

Next, we’ll cover the other common causes of short cycling and what you can do to help diagnose the problem to get it addressed as quickly as possible.

Corroded Flame Sensor

The flame sensor is one of the main safety features on your furnace. As its name suggests, the flame sensor is constantly monitoring whether your furnace is burning a healthy flame. If not, the sensor will automatically close the fuel valve and shut off the system. Over time, the sensor can become dirty, corroded, or rusty, causing it to misread the flame and shut down. While cleaning or replacing a sensor a relatively quick fix, it’s not something that should typically be performed by a homeowner. The repair involves high voltage and flammable gas, and should therefore be performed by a licensed professional.

Improper Size

Believe it or not, there is such thing as having too big of a furnace. When you have an oversized furnace, it actually heats your home too quickly. This matters because it causes your furnace to get stuck in a cycle of turning on and off constantly. This shortens the lifespan of your furnace. A certified technician from Owens will take the time to measure your heating area and optimize your home with the right-sized HVAC system.

Foreign Objects Lodged in the Chimney or Air Vents

From time to time, we see foreign objects and debris get stuck in the chimney vent. Your furnace will sense that airflow and/or exhaust is not circulating properly and the system will shut down. Diagnosing and servicing this absolutely must be done by a professional. Under no circumstances should a homeowner attempt to disassemble their chimney exhaust vents. Do not force another object into a vent in attempt to dislodge another item. Call Owens immediately for service.


There are the most common causes of short cycling. There are, however, endless other reasons for a furnace to short cycle. That’s why most furnaces have built in diagnostics to indicate where the trouble lies. When there is a malfunction, the system will communicate what the issue is through a series of blinking LED lights. This is called the error code. Take note… what color are the lights? How many times does it blink? This is especially helpful information to give when calling the problem into one of our technicians.

Have the following information readily available when calling Owens for service:

  • The make and model of your unit
  • Approximate age of unit
  • Warranty information, if available
  • Observed error code

We will help you through the manufacturer’s warranty process and help you understand what’s covered. We’ll also confirm if we can provide the service under the warranty claim. We service all brands and are well-versed in navigating the warranty process.

Short cycling can be frustrating. That said, the fact that your system can identify when something isn’t right is a good thing. Do not ignore short cyclign or the error code indicator lights. Instead, use this article to check for easy fixes. Call Owens if it’s not a quick fix. Have the proper information ready to expedite service. We will respond quickly, and walk you through our diagnosis and any options available. You can trust that with Owens, your short cycling system will get repaired quickly and correctly.

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