if it comes on initially, then the mother board most likely isnt the problem, it could be though but other checks should be made. When it starts blowing cold air, does it stop on its own? or will it run continuously until the board reset? if it runs continuously then its the board's way of warning you that a limit is over heating and has tripped as it's cooling the unit down. Check the obvious problems. filters, dampers, some kind of blockage to the air flow. The gas valve could be over firing but that usally doesnt happen on its own.
If the blower shuts down on its own, then the board is terminating the call for heat. find out what caused the premature termination. It can vary from bad tsat to bad tsat wiring to poor circuit grounding dirty flame sensor or a cracked Heat exchanger that knocks the flame out. sometimes the best bet is to get an expierienced tech to fix it and forget it. But good luck!
If the blower shuts down on its own, then the board is terminating the call for heat. find out what caused the premature termination. It can vary from bad tsat to bad tsat wiring to poor circuit grounding dirty flame sensor or a cracked Heat exchanger that knocks the flame out. sometimes the best bet is to get an expierienced tech to fix it and forget it. But good luck!
