Has anyone found in a 2009 model, the heater is either full blast hot or cold. I cannot get my supply air temp to get a comfortable mix of supply hot air with cool incoming air to a comfortable temperature.

 

I would guess your problem is the blending door mechanism or actuator is the problem.

Typically, the problem persists when the blending door cannot move, causing the door to be either closed or opened (hot or cold). If you have the auto climate control system, actuators will position the blend door for the proper mix of hot and cold to achieve the desired temp. Not sure if the technology has changed but vacuum lines were used in addition to an actuator. Accumulation of dust or pollen may cause some problems but the problem is more likely a faulty actuator.

If your system is the manual a/c, then you should check the linkage from the temperature **** to the blend door.

But the good news is your truck is still under warranty, so the diagnosis is your dealer's responsibility along with the repair.