I have a 2000 f250 4x4 7.3 diesel. I had problems with my a/c and controls for sometime now. my a/c was blowing threw the defrost vent. I was told my blend door was bad. I bought a new blend door installed it,still doing the same thing. I was told to check my vacuum lines. I check them, they were bad. I replace my vacuum lines and my vac pump as well. that fixed my problem blowing threw the defrost vent. I can control my air flow from floor,dash vents and defrost vent. the problem I have, I not able to control my temperature when I turn my center **** from red to blue. It blows hot air and the air that is coming out of the vents isn't very strong at all. if anyone has had this problem and fix it. I would appreciate your help, Thanks

 

Having the same problem with 2003 5.4 f 250. Just wide open hot all the time.