Problem: Medium heat only through floor vents & only when vent selector mode is Floor only.
Truck warmed up, temp guage about 40%; Current outside air temp range 60 - 68 (when TS)

Settings with MANUAL climate controls:
With fan #4 position selected (strong air flow) and temp selector hot :

Mode selector position:
floor + defrost - floor vents & defrost vents low air flow, slightly warm
floor only - warm (but not hot) air flow - no air from dash
dash only - cold (compressor clutch not on) & dash air flow strong - no air from floor
dash & floor - dash cool, floor medium
A/C dash & floor - dash cold, floor cold
A/C & Max A/C both very cold & compressor clutch on.

TS to date:
1. both heater hoses under hood hot (last radiator &/or heater core flush unknown)
2. Dex-cool coolant level full
3. HVAC fuses OK
4. fan control good, all 4 positions work well
5. mode control shifts air to proper vents
6. temperature control not controlling temperature correctly

Tried following youtube video on blend door actuator, but ran into following problems:
Blend door VACUUM actuator lever only moves when "floor only" mode selected.
Can't get the VACUUM actuator to slide up out of its bracket to move it out of the way to remove & inspect the
blend door actuator. (Didn't want to try forcing it, just in case my model is different & has screws or clips)

youtube video from 1:45 to 4:16 for visual orientation:
"GMC Chevy Blend Door Actuator Repair Replacement Fix Constant Heat Cracked Gear J-B Weld Repair"

blend door vacuum actuator
Any suggestions?