Why Does My Furnace Keep Turning On and Off?

Why Does My Furnace Keep Turning On and Off?

Our Expert Advice

A furnace may keep turning on and off due to several reasons, such as thermostat errors, short cycling issues, electrical problems, poor airflow leading to overheating, or faults in the flame sensor or ignition system. These issues can range from simple fixes like adjusting the thermostat or cleaning air filters to more complex problems requiring professional repair, like addressing electrical faults or replacing malfunctioning components. Regular maintenance is crucial to prevent these problems and ensure efficient furnace operation.

Jump to Some Common Issues

Why Does My Furnace Keep Turning On and Off?

One of the most common furnace troubleshooting questions we hear from our customers is, “Why does my furnace keep turning on and off?”. Normally, furnaces should cycle on only when the temperature in your home is lower than the pre-set temperature you have input at the thermostat. When the desired temperature is achieved, your furnace should turn off and only turn back on when required to bring the temperature back up.

However, some homeowners may find that their furnace is constantly cycling on and off, which can become more than just an annoyance – it can also indicate a serious problem. Luckily, there are some simple explanations for why this might be happening with your furnace:

Thermostat Errors

If your thermostat is faulty or is set incorrectly, your furnace may be signalled to turn off and on more frequently than necessary. Carefully review your thermostat’s settings and make sure they are correct. Next, consider the placement of your thermostat in your home, and move it if it is close to a heat source or direct sunlight, which may be signalling your furnace to shut off. A furnace turning on and off can also be the result of a faulty thermostat, so it may need to be completely replaced.

Short Cycling

Short cycling is often the number one answer to the question, “Why does my furnace keep turning on and off?”. Short cycling usually involves issues with the furnace itself, starting with a simple dirty air filter to a major issue with the circuit board. There are many other serious furnace issues that can cause short cycling, such as:

  • Cracked heat exchanger
  • Improper or clogged venting
  • Malfunctioning inducer
  • Dirty flame rods
  • Improperly sized furnace
  • And more

Electrical Issues

Sometimes, the problem may lie in the electrical system connected to the furnace. Loose wiring, faulty connections, or issues with the circuit breaker can cause intermittent operation. To address this, you should inspect the wiring and connections. If you’re not comfortable doing this yourself, it’s best to hire a professional. They can check for loose connections, damaged wires, and ensure that the furnace is receiving a stable power supply.

Overheating Due to Poor Airflow

If your furnace overheats, it will automatically shut off to prevent damage. This can happen if there’s restricted airflow in your system. This could be due to blocked air registers, a clogged blower wheel, or even a malfunctioning blower motor. To solve this, make sure all air registers are open and unobstructed. Regularly clean or replace air filters, and have a professional check the blower wheel and motor for any issues.

Faulty Flame Sensor or Ignition System

If the flame sensor in your furnace is dirty or faulty, it might not detect the flame properly, causing the furnace to shut off. Similarly, if there’s an issue with the ignition system, such as a dirty or malfunctioning ignitor, it can lead to frequent on and off cycling. Cleaning or replacing the flame sensor and having the ignition system inspected and serviced by a professional can resolve these issues.

These are just some of the issues that can cause your furnace to overheat, thereby triggering safety measures which shut off your furnace. Once it cools down, the furnace will start up again and the cycle will repeat over again until the problem is resolved.

Our team recommends seasonal furnace maintenance to avoid these potential furnace issues and to prevent short cycling from occurring in the first place. Regular tune-ups and/or replacement of broken and damaged components can ensure your furnace keeps running efficiently.

If you are still left asking, “Why does my furnace keep turning on and off?” we are here to solve the problem. Evam Canada is pleased to offer emergency furnace repair services to Mississauga and GTA residents. Our technicians are available around the clock to quickly respond to your furnace issues when you need us most!

Call us at 1-905-642-5544 for fast and friendly emergency furnace repair now.