Simple project i used to control old 5 pin power mirrors of Volkswagen golf III 1995
with modern 10-pin joystick controller of VW jetta 
Improved version i planned did include comparing value of known resistor to the resistance of the controller, but gearset inside the right side mirror broke, so i didn't develop this further. Main functionality is gained through control of the relay block. By reversing polarity and directing electricity to motors or defog resistors, satisfiable result was gained.
As mentioned before, right mirror's gears broke, so i didn't attach the planned mirrors to my car. Thus, i haven't tested these during winter or long, rainy seasons. Preferably, arduino and relay would be in a waterproof case, preventing any potenital problems caused by water condensing on the pcb.