Thank you both for your replies but my current belief is that the left mirror position reporting sensor (probably just a potentiometer on a wire
) is broken so when the control unit tries to set the position it runs the motor for a bit thinking the mirror is too low, then when the position doesn't change it gives up.
The electric portion of the mirror is fine but it has no memory function whatsoever. i.e. With the right mirror if I deliberately move the mirror and then request the memory position it returns to the memory position. The left mirror doesn't move at all.
It's far from a disaster, it just means adjusting the left mirror with the joypad instead of relying on the memory. I'd rather it worked, though, so I'll take it apart and see what I see. With any luck it'll be a broken wire that is easily repaired.
Is this a known failure mode of the mirrors? No memory on the left mirror, right mirror is fine?