The last thing you want in the middle of a winter night is to wake up cold. If you find your utility bills going up, smell a strange burning smell or a gas odour, hear unusual sounds, or find the furnace running for a short while, then turning off, have it checked at once by Your Local HVAC Team.

There could be a number of reasons behind a furnace running and switching off soon after. It helps to know your furnace better so you don’t panic when it malfunctions. Below are a few potential reasons.

Dirty Flame Sensor
A flame sensor can get dirty from carbon build-up. This could well be the reason behind the faulty furnace. Furnaces are usually located in the basements, laundry rooms or attics of homes. All these rooms are prone to dust that can settle on the flame sensor, causing carbon build-up. Even a slight film of carbon could affect its operations. The flame sensor is a slim, simple device that is located in front of the flame stream inside the furnace. Its job is to reveal the presence of a flame when the gas valve is opened.

When the furnace starts and stops, the burners are ignited but the flame sensor does not have enough time to detect the flame, so it shuts down into a safety lockout mode automatically for an hour or so, before attempting to try detecting the flame again. If there is no flame, unburned gas can build-up to dangerous levels, reducing efficiency and causing wear and tear to the unit.

How to Clean a Flame Sensor

  • To clean, use a ¼” hex head screw or wrench to open the screw from the unit to slide out the sensor for cleaning.
  • Remove the coat with light grit sandpaper, steel wool or emery cloth.
  • Gently wipe off the soot with a clean, dry paper towel.
  • If required, carefully detach the wire from the sensor end to work with more ease.
  • Fix back the wire in place, mount it back on the burner, get the door back in place and turn on the power.

Shut off the Furnace Power Unit

Whenever any electrical appliance breaks down, turn off the power of the unit at once. The same goes for your electrical furnace. You can switch it off like a light switch or shut the furnace down from the circuit-breaker box. If it’s a gas furnace, simply shut off the main gas supply of the unit before you inspect it. Unsure about the kind of furnace you have? Don’t take chances. Call our experts at Your Local HVAC team to take a look and repair it safely.

Double Check Installation

Once the main power is shut off and restarted, and your sensor is clean again, your furnace should resume operations again. Just double-check all wires and installations before restarting and the thermostat should be able to control the temperature by starting and turning off according to the temperature setting.

Broken Sensor

If it’s still not working, the sensor could be damaged. In that case, you will need to replace it. Remove the sensor following the same procedure mentioned above, and simply replace it with a new one instead of sanding it.

Your local hardware store may not have one but a contractor supply facility may be able to help you. Your best option is to call us at Your Local HVAC Team and do the needful services for you. Call one of our certified experts to give you a hand.