Blower motor runs won't shut off no heat
One or more limits are open.  You'll have to determine which one is open, figure out why it's open, and then fix whatever's causing it to be open.

If you look at the control board in the furnace/air handler, you may see a blinking light (or two). Count the number of blinks in the pattern, and compare it to the manufacturer's documentation. This will often point you in the direction of the problem. 

If there are no diagnostic lights, then you'll have to check each limit until you locate the open one. If you don't have the tools or knowledge to work on HVAC equipment, it may be time to contact a local HVAC company.