If you have a gas furnace, do this today [View all]

[jmowreader]

Gas furnaces don’t run their burners all the time, just when they need to produce heat. When the thermostat commands them to make heat, first an igniter - an electric heating element or maybe a spark producer - and the blower turns on. When conditions are right to light a stream of gas then the gas valve opens to allow fuel into the chamber, and it is lit. The Igniter shuts off then and gas flows until the thermostat tells the furnace to stop making heat.

The furnace needs to know if the gas is burning - if it isn’t and it keeps flowing your furnace could explode and burn your house down - so there is a metal rod called a flame sensor in the path of the burner flame. There’s usually also an optical sensor in there so the furnace can see the flame, but the rod will always be there. If the rod gets crudded up with soot, dust, whatever, it can’t sense and your furnace won’t work.

You COULD pay a heating company a couple hundred dollars to come out and clean this, but it’s something anyone can do. This is how.

You will need a Phillips screwdriver to open the furnace cover, a 1/4” nut driver to take the flame sensor out, a green scouring pad to clean it, and a damp cloth to clean the face of the optical sensor.

Turn the furnace off at the breaker panel and remove the cover. It’s the one at the bottom of the furnace. There are normally two screws holding it on and there’ll be a placard above it telling you you’re gonna die if you run the furnace with it off. Put the screws somewhere safe - if you have a magnetic bowl use that - and lift off the cover.

Look at the burner chamber and you’ll see the flame sensor. It’s a metal rod about three inches long with a wire coming out the top of it. Pull off the wire, undo the one screw holding it in with the nut driver and lift it out.

Gently scrub the rod with the scouring pad until any soot or debris is gone.

Reinstall the rod and hook the wire back up.

Gently wipe off the lens on the optical sensor. You can do this with it still installed.

Reinstall the cover and turn the furnace back on at the panel.

It’s best to do this while the furnace is still able to make heat, so you don’t come home from work at 3 am to a cold house.