you are about gain knowledge of evil. Don't bite the apple or swallow the pill because you will never being the same. If you wish to stay in blissfull ignorance don't read further.
Well after putting the control board back in and still having problems the control board is flakey. I got it to start once. It is supposed to open the solenoid valve and run the sparker for several seconds and if it senses a signal from the sense lead that is the small wire next to the spark plug wire it continues to run otherwise it shuts down. The sense leads is not a thermocouple but a voltage source. When 12V
goes to the gas solenoid it also sends 12V
to the sense lead. The control card measures the current to ground and when it senses a current it keeps things running. Current flows when the air becomes ionized by the flame and becomes conductive. When mine started everything worked like it is supposed to and the fan ran while the furnace was hot even after turning the thermostat off as it should.
It appears that the circuit that tells it when to start is messed up. This circuit is supposed to wait a few mins after shutdown before it lets you start back up again.
The board is supposed to go through a cold start sequence as soon as the fan motor is up to speed and the sail switch closes and sends 12V
to the card. There is also a thermal switch in series with the sail switch. The thermal switch is on the front face of the control board housing. I could measure 12V on the input of the control card but it would not initiate the start sequence.