cx complaint unit is not heating. inspected unit and found 246.4vac to terminal block. i found polarity was good. i removed back cover and found upper thermal cut off was faulty and also found thermostat was faulty. i replaced both and found unit now heats. i then checked air flow and found exhaust vent hose was fully clogged. I advised cx to replace exhaust vent before using unit. unit now checks good.