Goodman furnace - works most of the time. Then, it will give the one-blink indicator of ignition failure. We either wait for it to cycle (which can take 30m-1hr) or turn off the power to the furnace and turn it back on which works.

This is odd. 80% of the time it is working properly. Then, why wouldn't it? I've stood in front of it - motor runs, gas is flowing and it won't ignite. My only guess is flame sensor or ignitor, which I'm leaning towards ignitor.

QUESTION: I thought ignitors are either working or their not. Thoughts?

UPDATE: Thank you for the replies thus far. This seems to happen most often in the morning, rather than mid-day or at night. Lately it kicks on for a little bit in the morning on first run then stops and cycles with the one blink. Turning the furnace off, then on, then adjusting the thermostat tends to get it to work and it'll work all day. Lately the next day it repeats itself.

  • Hello, and welcome to Home Improvement. When did this start? What model furnace is it? And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Feb 16 '20 at 18:50
  • It's not terribly uncommon for a gas furnace or boiler not ignite. That's why there are "flame proving" mechanisms in them. When was the last time it was serviced? It may need to be serviced or a part replaced. Igniters can weaken (happened in my Viking stove) and then fail to operate properly. You need a tech to take a look at it. – George Anderson Feb 16 '20 at 22:39

The startup of a gas furnace usually sees the controller moving through a series of states. The controller would verify that high temperature limit switch is not activated, the exhaust pressure sensor shows no pressure, then switch on the inducer fan, then verify that the exhaust pressure shows pressure, then turn on the igniter. I don't know if any common controllers verify the igniter (current consumption, heat produced, etc) or not. After a delay the gas valve is opened. As long as the gas valve remains open the controller continuously looks for the flame proving sensor to verify that the burner is still burning.

If your furnace always ignites when there's a call for heat but subsequently extinguishes before the call for heat was satisfied then the problem could be anywhere: flame sensing, exhaust pressure sensing, high limit cutout.. flame sensing is probably the most likely, though, because arguably it experiences the most extreme operating conditions.

On the other hand, if it sometimes doesn't ignite at all, that's more likely to be an igniter problem than a flame proving problem. I agree it seems most sensible that an igniter might completely fail, but I guess there must be some intermittent failure modes possible too. You could remove it and visually inspect for cracks or other signs of failure, but be prepared to deal with the possibility that this might push it from partial failure to complete failure!

  • It can also be the electronics in the starter, I have seen cracked hot surface elements work but they usually fail not long after starting to fail. Use caution with new elements only purchase from a good vendor. I have received more than one broken in shipping, do not touch oil on your fingers creates a hot spot and can cause a failure in a day or two.+ – Ed Beal Feb 17 '20 at 14:34

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