What I've seen and fixed for a friend's who's fan would come on but not light---
*** First, though - disclaimer. ***
I'm an electrical engineer. Do not fix your furnace if you're not completely familiar with a meter, electronics, and a soldering gun. Messing this up can cause a safely issue, fry your board or start a fire.
When you open the access hatch, there is a board, or "brain". It has a connector on it with a bunch of wires.
* Take the connector off and inspect the board and connector for signs of overheating.
* Look for a pin that is brown/burned, and scorching on the board.
* Plug it back in, turn on the furnace, and see if there is voltage present on the board side and the pin side.
What I found was the pin that goes from the "brain" to the propane solenoid was burned on the board itself. The solenoid pulled more amperage than the connection could handle. The propane solenoid was not opening.
The plug I'm referring to is not a safety, simply a disconnect. To fix it, I--
* removed the board
* cleaned the trace on the board just before the plug
* soldered a 14ga wire directly to the board
* ran that wire to a crimp-style spade connector
* cut solenoid the wire off the plug, and added the female spade to the solenoid wire.
* plugged in the spade
* tape'd it up with electrical tape
IMHO this should be a recall from the manufacturer. What I found could very easily cause an electrical fire. Cleaning the connection will not last and will simply overheat and burn the board and plug again.
