[quote=bluezone]make sure there is not a blockage in the fresh air supply - snow, leaves, childrens toys, debris blown around in the wind...

make sure you test the flame sensor, heat exchanger sensor and the pressure switch for the power vent as they are usually connected

do you think that was the original problem or was the main board also bad?

[/quotYes on mother board. It worked up till a few days ago then crazy things started to happen. The mother board had three fried diodes. But again there had been no maintaince on it at all
so it might have been avoided as for the board issue
"If there must be trouble, let it be in my day, that my children may have peace."