Auto dimming mirror - how do I know if it is working??

[Rybky]

Might seem like a stupid question but how do I know that my auto dimming mirror is actually working? Because I don't seem to notice any difference in the tint during the day or at night, it always seems quite tinted!

My mirror has a light sensor on the back (so facing forward) which I assume is ambient light sensing, and another under the mirror facing back for detecting a bright light behind. No on/off switch that I can see.

I tried a daytime test of covering the ambient light sensor with my finger then shining a light (mobile phone screen) on to the sensor under the mirror, no change.

Is there a proven way to test these? How much of a tint change is there normally?

Are they known to fail?

Thanks!

Adam

[graeme86]

One way is if you put the car into reverse...it will undim...quite noticable reversing out of dark garage on a sunny day.

Your test method would work with a much brighter lightsource as well like a proper torch.

The only failure they usually have is that the fluid leaks out of the internal LCD....then you get a sort of "half filled glass" look to the mirror surface...or the fluid leaks out of the mirror housing all over your dash.

[Rybky]

Thanks Graeme. I will check it out more over the weekend, the reverse undim should be easy to spot and I will try a proper torch to test it too, did think the phone screen may not be bright enough!

Adam