Mechanics

F150 HEATER ONLY BLOWS ON DEFROST

2003 Ford F-150

Heater problem
2003 Ford F150 V8 Four Wheel Drive Automatic 230000 miles

Electronic climate control unit. Heater is currently only blowing on defrost. A/C works good on vents, floor and defrost. Heater will NOT blow on floor. I replaced the heater unit once and it worked ok for about 6 months, but then defaulted to the same defroster setting only. Is this a vacuum leak or did the ECU fail again? I now have 2 suspect failed heater units. Are these repairable? If it's a vacuum leak, where should I start looking?
Avatar
F150fxrguy
June 20, 2010.



I would start with the idea of a vacuum leak. Start by checking under the dash and the hood. That would be my first guess.