iI have a 05 F150 XLT. The heater works great, however when I turn the control **** to defrost or any other position, it stays in the foward vent. Thats the only position it knows. I have 41k on it I bought it used. Any advice would be appreciated.

Thanks,

Jim

 

Sounds like the flow control door is stuck (bad actuator?) in one position. No/low vacuum would cause the system to "failsafe" to the defrost position.

Steve

 

The 04 and up F150 doesnt use a vacuum controlled system. All of its actuators are electronic. The mode control actuator may be stuck due to a linkage problem, bad control motor, or possible a bad control head. The mode control actuator and linkage is on the driver side of the heater plenum.

 

Homer -

Thanks for the info on newer 150's. Do you know if these have a defrost "fail-safe" also, maybe spring loaded to that position when power is lost?

Steve

 

I have never seen such a failsafe mode on the electronic systems.

On the rare one or two I have seen with a failed control motor, it will act up oddly or make so much noise you will take it in to fix it before it fails completely or fix it yourself.