The igniter in a gas furnace provides the heat source that starts the combustion process needed to warm your indoor air. A glow bar igniter has an M-shape filament that lights up red or glows when hot. If your furnace has recently stopped heating and you don't see the igniter glowing when it should, you should test the igniter to see if the part has failed.
You can test a glow bar igniter using a multi-meter to check for continuity or a continuous electrical supply to the part. You will first want to isolate the igniter from the furnace. Use your owner's manual as a guide if you need help getting the igniter out of the furnace and make sure you turn off the power and gas supplies before you do so.
Here is how you can test that removed glow bar igniter for continuity.
Things You Need:
- Isolated glow bar igniter
Step 1: Testing Setup
Check the igniter for signs of cracking or singeing. If you see either problem, discard the igniter immediately and install a replacement.
Set and calibrate your analog multi-meter if that's the style you own. Turn the setting dial to the lowest reading for ohms of resistance. Touch the two probe ends to each other and see if the needle goes down to zero. If the needle stops above zero, manually move the needle to zero while the probes are still held together to calibrate.
Using a digital multimeter? Turn the dial to the either the lowest settings in ohms or to continuity with tone, which only tests for continuity. No further calibration is needed.
Step 2: Test the Glow Bar Igniter
Lay the glow bar igniter on a flat surface using caution to never touch the filament end of the part. Locate the two terminals in the wire connector socket located on the opposite side of the part than the filament. Touch one probe of the multimeter to each of these terminals.
Check the reading on the meter to see if the ohms is between 50 and 400. If the Ohms reading falls within the indicated range, the igniter has continuity, and your furnace has another issue causing the heating failure. Alternatively, if you have your meter set to continuity with tone you simply need to wait a few seconds to hear if the continuity confirmation tone will sound.
If the number doesn't fall within the ohms range, the needle doesn't move, or the tone doesn't sound, your furnace needs a new igniter. Contact a heating repair company like Advanced Heating & Cooling to install the new part.