2005 Chevrolet Avalanche - HVAC on one side only

heat/cool control. selector works ok on passenger side, selector makes no change on driver side. yesterday it was hot air only , this morning it was cold air only .this is messed up only on the drivers side.

One or more HVAC actuators have gone bye-bye. I think there are 4 on this truck. They cost about $50 or so. 3 of them are fairly easy to get to, the 4th a bit more difficult. Common failure, any shop should be able to handle it.