Our furnace would not light off at the end of the spring season.
I had bought a new igniter and was investigating how to replace it. In doing this I sprayed some WD40 and Penetrating Oil into to free up the exhaust stack into the heat exchanger. I decided to check it out again and low and behold it lit off. I think the WD 40 hit the contact wire fastener to the igniter which I cannot see with the exhaust stack still stuck. So I think that it was simply a bit of corrosion on the connector which the WD 40 has freed up!
A lot in Melaque Mexico in winter and Victoria BC in summer - 2000 Fleetwood Bounder 31 W
03 Tracker ZR2 Towed
Excalibar Towbar and SMI Stay in Play braking
I do not know about YOUR furnace but on mine the same wire that carries the oh, roughly 1,000 volt spark power for the ignighter, also carries the less than 1/2 volt signal from the thermocouple to tell the control board FLAME ON.
And though the kilovolt won't much be bothered by a poor connection.
The half volt will. Thus our fix sounds quite possible.
WD-40 is after all a cleaner.
Nothin adds excitment like something that is none of your business
Kenwood TS-2000 housed in a 2005 Damon Intruder 377