I am unable to heat up the air on the driver side of my truck. I swapped out the electronic control with a friend and that did not resolve the issue so I beleive the problem isa bad actuator in the air flow system. I took the dash apart but could not locate the actuator. Anyone know where the actuator is located?

 

what truck is this?...if its a gmt800 (99-06) its at the bottom of the case

 

You were right on the driver side temperature actuator was on the bottom of the A/C case. I replaced mine and all is good except my wallet. The temperature actuator cost $228.