Heater blowing cold air depending on switch positions

[Silver Fox]

I have a 2002 Tahoe. When running the heater in the vent/floor position and temp control to full hot, it blows hot air fine. When you turn the temp controller just below full hot, the air becomes very cold at the floor. The wife has found a sweet spot below full hot periodically that works but rarly. Any ideas? My thoughts move to the selector itself but I do not want to spend money without somehow verifying first.

 

[MisterNiceGuy22]

This for the front or rear heat/ac? is set up for dual zone n rear seperate control? I had the same issue with the rear stuff, I fixed it somehow but accidentally reversed the actuators..so now in the rear if i tun it to cold it blows hot n vice-versa.. any details bout your heat/air setup might help me help you out..