My furnace worked fine last Thanksgiving. Made a little trip this week and it got down into the 30's. Turned on the furnace and here is what happened: Blower turned on, I heard the burner ignite, ...
If the burner and the blower motor are stopping at the same time, it appears you are loosing the 12 volts to the furnace. The blower motor should never stop during the burn cycle. Please post the model of your furnace so we can look at your specific wiring diagram and give you some more advice. Wiggle the wire connections at the furnace and see if you can duplicate this motor stopping problem during the initial start cycle.