Basic Troubleshooting for a Malfunctioning Furnace Sensor

Furnaces have built-in safety measures to ensure that noxious gases and fumes don’t leak into your house. A key component of the furnace’s safety circuit is the flame sensor, a small metal rod with a porcelain base that monitors the flame in the furnace through an electrical current. When the flame goes out, the furnace sensor immediately shuts off the gas supply to prevent it from leaking into your home and causing carbon monoxide poisoning. As such, it’s important to make sure the furnace sensor is working properly.

How can you tell if the furnace sensor is malfunctioning? By keeping an eye out for certain warning signs. Stone Heating and Air, a trusted heating and air conditioning company, lists them below:

Troubleshooting for a Malfunctioning Furnace Sensor

  • Furnace shutting down a few seconds after starting

  • Cracks in the sensor’s porcelain base

  • Soot or rust on the tip of furnace sensor

The Usual Culprit Behind a Malfunctioning Furnace Sensor 

While corrosion or wear and tear are possible causes, the usual culprit behind a sensor malfunction is carbon buildup. That’s why it’s important to routinely clean your furnace’s sensor.

How to Clean the Furnace Sensor 

  • Shut off the furnace’s electrical supply – Simply turning it off isn’t enough—you need to shut off the electricity supply. Remember: safety should always come first.

  • Remove the heat sensor – The sensor is a rod-shaped device in the path of the burner. Loosen the screws and remove it from its bracket.

  • Carefully remove residue on the sensor using emery paper or light-grit sandpaper – After cleaning the sensor, wipe off the remaining dust using a lint-free cloth.

  • Reattach the furnace sensor – Make sure to tighten all screws fully after putting them back in.

If you’re still encountering furnace issues after cleaning the sensor or aren’t comfortable with handling sensitive furnace components, you should schedule an appointment with one of your local home heating companies. As a rule, your furnace should be inspected by a technician at least once a year.

Are you looking for HVAC technicians near you? 

Stone Heating and Air is one of the most trusted HVAC companies in the state. To schedule an appointment, call us at (541) 855-5521 or fill out this form.

Request An Appointment

Please subscribe me to the newsletter
This field is for validation purposes and should be left unchanged.

Related Content


When Is the Best Time to Have Your Air Ducts Cleaned?

One key aspect of maintaining indoor air quality is clean air ducts. However, a common question that arises is: when is the best time to have your air ducts cleaned?...
variable-speed fan coil

Variable-Speed Fan Coil Units Can Make All the Difference

It may seem counter-intuitive to think about replacing or upgrading your heat pump as the weather is warming up, but now is a perfect time to make home improvements for...
spring maintenance for air conditioning

It’s Time for Spring Maintenance for Air Conditioning Units

Mid-March marks the beginning of Spring with the Spring Equinox, and that means sunny, warm weather can't possibly be far behind! Yet, as the gentle warmth of Spring appears, it's...