One side of the cab only blows hot air when AC is turned on. Help...

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.