without a pic its hard to say, but there is a heater resistor board towards the bottom of the blower unit, they are notorious with overheating and going bad, there are new ones that come with new wiring and connections to solve that problem, i had it happen to me two years ago during the winter, took me a week to finally figure out thats what went bad, and another week to get the new one with the new connection and wires, nothing like two weeks without heat! takes less than 30 mins to replace/install it, havent had a problem since! the only problem is that its wayyyy up under the dash almost to the firewall, so the upside down contorting way to reach it kinda sucks!
2003 WJ Overland, 4.7HO, D30 & D44A (1 tons going in now!), RC Long Arm, lifted 4" Front 6" Rear, RC 2.2 4" Shocks, JKS track bar, custom hi-steer, 35" Procomp M/T's on JK rims, beefed up Overland rock rails, custom skids and dif gaurds, Rugged Ridge 8500 synthetic winch in custom hidden mount