I have a VW 2000 beetle mirror control (Joystick) that has ohm values for outputs that are read via VW window controller.
I'm pretty sure every remote mirror adjustment switch/joystick I've ever used is a 4-position (plus center-off) switch. There is no proportional control... You push the switch/joyswitch in one direction and the mirror moves until you release the switch/joystick.
Without a schematic or wiring diagram you are working in the dark and we can only guess.