One side of the cab only blows hot air when AC is turned on. Help... on 2005 Chevrolet Silverado 2500 HD

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
Passenger side of the cab only blows hot air. It blows hot air every time I turn on the AC, the driver side works fine, but the passenger side only blows hot air no matter what the temperature is set too. I have the digital temperature controls on the dashboard. Any help would be appreciated.

Thanks in advanced...
(1) Answer
my a/c stopped working completely so took to dealer and they re-programed to fix.
now after a month mine is doing the same thing -passenger side not working but it ''s only half the time, the other half it works properly. my thinking is that the program in the computer got messed up again so will go back to dealer at his cost of course. call a dealer to confirm.