Auto Air Conditioning & Heater Repair: 2004 Ford F350 Diesel, ford f350 diesel, ford tsb

Question
The air flow director is stuck on Defrost no matter where I turn the knob the air continues to come out the defrost.  THe only thing that works on the knob is it will turn off when moving to OFF or comes out the defrost when turning it on.

Answer
Don,

There is definitely something wrong in the climate control mode selector system, and it's usually a vacuum issue. If the control head doesn't receive the appropriate amount of vacuum, then the actuator is unable to change positions. I'd check for vacuum and work from there.

Note: Ford TSB#05-17-4 directly references a fault in the Vacuum Pump on certain models, providing the vacuum lines are in good condition. Ford even outlines the prevailing symptom being climate control stuck on defrost. Additionally, the 4X4 may be inoperative as well, as it depends on system vacuum for proper operation. The fix is replacing the Vacuum Pump.

Good luck!