03 avalanche blowing hot air on driver side and cold air on the passenger side

Fischergurl_2

I have a 03 avalanche and one day the air stopped working on the driver side and still blows cold air on the passenger side

Mr_Shiftright

Probably a blend door has broken or the motor that actuates it has given up. A good scan tool should be able to identify the problem exactly. Do you have dual controls for heat and AC?