There is no popping noise from the igniter, and the gas valve doesn't open.
Your igniter coil is bad. I would replace igniter and igniter coil. Checked flow charts for this furnace, Russ
The igniter connects directly to the circuit board. If the igniter is bad, would this keep the same voltage going to the gas valve?
What voltage should be going to the gas valve to open it?
As stated before, " Forced draft safety switch looks OK (closed circuit when induction fan runs, open circuit when it's not). Limit switch looks OK (closed circuit). " As for the circ fan safety switch, the system doesn't get far enough for the circ fan to come on in the first place.
The igniter coil is on the board, and I already replaced the board.
If the igniter is bad, would this keep the same voltage going to the gas valve?
The LED on the circuit board flashes twice then off. Then the same sequence is repeated. There is no code listed anywhere on board or on the unit that I can find. The board is PROTECH Integrated DSI control 62-23599-05. No documentation came with the board to tell what the code means.
1. Is it vacuum or positive pressure that closes that switch? (it definitely closes with a little vacuum)
2. What is on the other side of that hose (where it goes into the induction fan housing)?
3. Should I be able to blow through into the fan housing (in other words, could it be stopped up with something?
Yes it could just take paper clip and clean fitting. Russ
Success at last. That was it. That port was stopped up.