Schocki

Thanks for all your advice first!
I checked the vacuum solenoid that allows vacuum flow to the footwell actuator and regardless of the HVAC slider there is no vacuum. Furthermore the previous owner DISCONNECTED the vacuum actuator from the footwell flap hinge and used it as a cablemount with the help of a cable tie. That allows the footwell flap to stay open all the time regardless what you do! I connected everything again and the footwell flap is now shut and very airtight and the airflow through the center vents and door vents is greatly improved!
I will pull the vacuum solenoid assembly next and now there are anly two things that can be the cause for the problem:
1. The footwell solenoid is not working
2. There is no power to the solenoid
All other functions and solenoids are working fine. I think that the previous owner had a problem with the footwell flap being shut all the time and due to the generally cold temperatures in Germany, he had cold feet all the time
That's why he disconnected the actuator and never checked the solenoid.
I wil look into the matter later because it's already 96F and it's just a PITA to work on the car in my non AC garage!
I will keep you updated