Auto Air Conditioning & Heater Repair: 2003 F150 Lariat A/C, thermostat controls, digital thermostat

Question
I have the Digital Thermostat Controls in my F150, and when I select A/C, it will blow out of the dash only if the fan is set very low. The second I set the fan to anything other than low, it redirects and comes out of the defrost vents. This also happens if I am taking off from a stop or heading up hill, defrost only. Heading down hill, it works normally. I've taken it to 2 different Ford Dealers, and neither of them were able to diagnose the issue. The truck runs perfectly, and the A/C is very cold. It is a FX4 SuperCrew with the 5.4 153000 miles.

Answer
Check your vacuum lines in the engine compartment.  Let me know if you are testing it while you are driving or just at idle.  If when your are moving then test it while at Idle.  Also test when system is at 72 or so and let me know what happens.  If you are not sure you can call me (Candy) at 305-468-8387 M-F 7:30 AM to 5:00 PM.