Multivan rear temperature control fault

[ease2nd]

Hi,
I have Multivan, 2016
the temperature control of rear seat area is not working.
I got it checked and the workshop gave me the feedback that the actuator,7E0907512, is the problem.
Then I have replaced the actuator myself, potentiometer was around 5k and motor was working on 9V, but still it is not working.
Could be any other issues like wire harness or something?
What would be the next thing to check?
Thank you.
BR Seungbok

 

[ease2nd]

adding to this,
the HVAC is working if I adjust the lever of the actuator, it gives hot air and cold air,
but I just cannot control it from the dash.