• The unit is working as prescribed but there is an air leak, a clogged distributor or a calibration issue here, first the air leak. The unit is leaking air around the motors or around the lower seal or the heater assembly, first make sure the motors are seated properly (gaskets-#31463-$8.00) and working. (motors-#HMOT001-$86.68) You should be able to see the leak by the tell-tale black carbon dust around the silicone sealant, you may find this in the lower seal or the heater panel seal, also the silicone will be loose or flapping, if so, reseal and let cure for 24 hours before you turn the unit on. Second, if the distributor is clogged (Distributor-#HFOA005-$60.00) then the super heated air is not circulating enough and the response time from the thermistors is too slow to turn the heater off, the motor heat continues to climb and the heat runs away. if this is the case then the distributor would need replacement, click for the instructions for that procedure. Third, the calibration is out, click here for the calibration procedure.  One of these things should solve the heat problem.  if not then the circuit board has a failure and needs to be returned to our service department for evaluation and repair.