Does the blower run? This is very obvious when you turn the blower switch on. If it does, can you change air direction by pushing the heat or defrost button? If you can, then it is the linkage between the temperature control adjustment and the air flap that allows air to flow across the heating coil causing your problem. If no fan, check fuse. If no change in air direction, check for vacuum leak, If no temp increase, check cable linkage to air flow damper.