I have been researching how to diagnose this intermittent lighting issue with my furnace but the common issues do not seem to apply.

  1. Blower turns on
  2. Ignition coil turns cherry red
  3. Sound of gas blower starts
  4. No ignition, ignition coil dims, and blower remains on

I've uploaded a video as well: https://youtu.be/Y9umhFh6_gc

I am trying to figure out a strategy for determining what part I may need to order and replace.


Ended up having a technician come out in fear of the intermittent failure becoming permanent in this cold winter.

Issue with this old furnace turned out to be that the gas valves were dirty blocking gas flow to some degree. The technician disassembled and cleaned the valves and went on his merry way.

I learned this is a good yearly maintenance for old furnaces like this.

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  • Thanks for answering your own question. Please give yourself a check-mark so everyone (and the system) know this has been resolved. – FreeMan Sep 15 at 14:04

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