It is a rudd gas furnace. Changing the thermostat to off does not fix the problem

While this is clearly a problem I personally would not worry about it. I turn my stat to ON the day I move into a home and there it stays until I move out. ON 24/7 makes the home more comfortable and uses just a very very small amount more of electricity than the AUTO setting. Does your furnace have a light switch type switch on a box on the side of the furnace?

Do the burners ignite when there is a call for heat, or does the blow just constantly run and no heat is produced at all. If the burners don't ignite when there is a call for heat, you most likely have a tripped high limit or rollout switch.