Testing Door Mirrors

[Deadpool]

I've noticed that the auto dimming door mirrors have both stopped dimming but the rear view is still ok . Does anyone know of a way to test them. I do have a spare somewhere as I had to replace the passenger door mirror as the monkey metal all disintegrated.

 

[MrKis]

If you cover the sensor at the back of the rear view mirror, they should all dim. If you have that option of course.
I'm sure the workshop manual has a better way with a multimeter under pinpoint tests.

 

[Deadpool]

Thanks, I've tried that but just the rear view mirror dims. I will dig out the spare mirror and see what happens.