As previously posted I rebuilt entire HVAC box and installed during early covid down time. Recharged a/c and thought everything was fine till I tried to use the heat. So I checked the temp control unit and actuator motor (what an mf'r to remove) both working. Plastic coupler not broken so I used plyers to try to turn and won't budge. A little more force and I snapped it off. Ordered heater treated replacement but what is stopping it from turning freely, wondering what I might have done wrong or where it could be hanging up. Planning on using the new metal coupler to really put some force on turning it. Any advice out there appreciated, thanks!

 

Should be able to turn the blend door with your finger tips. If it's stuck, time to open up the box again.