My furnace's model is GMNT100-4. I replaced my ignitor with this new ignitor

I only worked for a couple hours. I never touched the carbon. Only held it from the silicon. Though my access to the ignitor was extremely restricted. I suppose I had it scratched.

Now when I read its resistance, I'm getting OL as opposed to 90 that I was getting yesterday.


  1. This site says:

Due to their extremely fragile nature, the B1401018S sodium carbide ignitor has been superseded by the 0230K00001 sodium nitride ignitor. The 0230K00001 sodium nitride ignitor has proven to be seven times stronger than the B1401018S sodium carbide ignitor, making it a wise choice when repairing your broken furnace

Can scratching the ignitor cause it to go bad? Internet only mentioned (hand) oil. I suppose it can.

  1. Should the furnace ignitor have any voltage before and after turning on the furnace?

While I had voltage reader connected to the cable coming into the ignitor, I attempted to manually ignite the furnace with a lighter stick.

As soon as I turn on the furnace the voltage shows 7V.
After 20 seconds or so, it turns to 120V.
After I spark the gas with my lighter, it goes back to 7V.

Can the 7V cause it damage?

Is there any other tip or instruction that I should have done? Or maybe I bought the wrong ignitor...

  • 1
    Just as with halogen headlight bulbs, this seems to be a good opportunity to wear a fresh pair of latex/rubber/whatever gloves.
    – FreeMan
    Commented Feb 1, 2023 at 16:40

1 Answer 1


The ignitor works by creating a spark. The reason you don't touch it is so that the oil from your fingers does not stop the spark from forming. Otherwise they are not that fragile.

  • A slight scratch is unlikely to have damaged it.
  • It would require a much higher voltage across the tip/point to generate the spark, so 7V is nothing.

When you turn up the thermostat to initiate your furnace, you might notice a clicking sound before the warm air arrives. That noise comes from the furnace ignitor.

As its name implies, the furnace ignitor creates a spark, igniting the gas to heat the air circulating through your home.

From hvac.com

Don't be afraid to try a good number of times. If it's clicking then it's probably working and there is no gas. If it's not clicking then you have a problem.

  • Try what a number of times? FWIW if I manually ignite the furnace, when the gas comes through (which is typically after 25 seconds), then the furnace fires up and starts heating the house...
    – Honey
    Commented Feb 2, 2023 at 18:16

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