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The furnace does not ignite. I am getting 3 green flashes from indicator.

When heat is first turned on I hear a louder hum/buzz noise that is louder than the constant transformer hum while the system is attempting to fire-up and the green light is normal steady on, no blinks. This louder noise of a motor or relay hum lasts for about 45 seconds and then stops and the green light begins 3 flash routine.

I don’t hear a fan motor or booster motor running during the attempted start-up. I think the combustion booster motor or relay may be the trouble.

Do you have a diagram or manual that shows exactly where to find these 2 parts? Is the combustion motor located in the exhaust duct where the 2 tubes from the air combustion switch connect?

What do you think might be the problem?

Any help would be much appreciated.

Thanks,
-MarkF

Mark,

It sounds to me like the noise you may be hearing is the combustion motor humming because it is siezed up. You should be familiar with the sound of that motor running and if you don't hear it, that's my guess. Robert should answer this soon, he's the guru. If you're comfortable removing the combustion motor, you can check it by trying to spin the wheel. If it doesn't spin, or is tight, that's your problem. Make sure power is off to furnace if you decide to remove it.

Hi Mark,

Combustion motor is midway of furnace on right side. Has an air vent pipe connected to it and tubes running over to disc shaped pressure switch.


IF it is not running, see if it has 120VAC coming to it. Trace wires back to board, unplug connector and test across corresponding pins/holes.

IF you have 24vac across W and C at board, then you should have 120vac at the combustion motor wires corresponding pins/holes.


Thanks,
Robert

Thank you guys!!! I will do that.

Regards,
-Mark

Just let me know what you have.


Thanks,
Robert

Mark,

What was your final result?