Want a Warm Home yet the heater keeps Turning on and off? (Find out Why + Tips to Fix it)

Note: The information provided here is only intended as a guide. Always contact a qualified and licensed technician if the furnace is not working properly. A faulty heater can cause a fire.

A working furnace helps keep your home warm and cozy during those cold winter days.

But what if your heater is not working properly and instead cycles on and off repeatedly every few minutes before shutting down? What is the likely problem then and can you fix it?

This post looks at the common reasons why the heater may cycle on and off or shut off after a short while. It lists some checks you can do to identify the fault faster and lastly suggests some fixes that may help you get the furnace up and working reliably so that you have a warm home.

What Causes the Heater to Cycle on and Off Repeatedly? (Suggested Fixes)

While there are several possible reasons that can cause the furnace to go on and off, one likely reason is that the furnace is shutting down as a safety precaution because it has attained the high temperature limit. This can be caused by:

#1. Poor airflow around the heat exchanger causes a buildup of high temperatures in the furnace.

Check the vents going out into the space to be heated and the return vents for any obstructions. Remove the obstructions and run the furnace again to check if the problem clears.

#2. The sensor is not able to detect the flame and turns off the gas. Does the LED light when the flame comes on? If the heater is not able to detect the flame it will shut off the gas supply as a precaution. Clean the flame sensor and test the furnace again.

#3. There is a problem with the thermostat. It may not be set correctly if recently replaced or it could just be faulty too. Contact a qualified technician to help you with this. If you have the skills, you can try jumping the thermostat and checking if the furnace still cycles on and off or shuts down after a few minutes.

If it runs well without any issues after bypassing the thermostat, replace the thermostat and run the furnace again to check if the problem has cleared.

#4. is the furnace sized appropriately for the room? If oversized, then it can shut down as a safety precaution. This is more likely to happen with a newly installed furnace. If the furnace has been working well before then this is not likely to be an issue.

#5. The control board in the furnace is faulty. If you’ve checked the vents and they are clear of any instructions, replaced the air filters, cleaned the flame sensor, there are no error codes and the issue still persists, the furnace’s control board may be faulty. Contact a qualified technician to support you on this.

Closing Thoughts

If your furnace keeps coming on and going off, confirm that there is sufficient airflow and that the vents are not blocked. Other possible reasons why the heater may cycle on and off are a faulty thermostat or a faulty control board.

Hope this helps!

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