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Auto-dimming rear view mirror - Can I just check that this is functioning correctly?

11062 Views 7 Replies 4 Participants Last post by  bartwins, 
R
Hi to all

Have just bought a used auto-dimming rear view mirror from Ebay and fitted it to the car - all fitted in nicely and the wiring loom was where I expected it to be. However, I'm not sure that it actually works correctly.

The mirror was fitted with engine off / key out of ignition uncompletely fitted and plastics replaced.

When engine on, and with the AUTO button at the bottom of the mirror OUT (or not pressed in), I shone a focussed beam of light (admittedly in the daytime) from my maglite onto the light sensor on the front - nothing happened. I then tried covering the light sensor on the rear with my finger - nothing happened, and then finally tried shining a focussed beam whilst still covering the rear sensor - and again, nothing happened.

Then I pressed the AUTO button in, so that it clicked down. Again, shone a focussed beam onto the light sensor on the front - nothing happened. Then, I tried covering the light sensor on the rear - this time, the glass dimmed nicely and went dark (I presume to replicate what happens in night-time driving?), and then thirdly tried shining a light on the front (glass) sensor whilst still covering the rear sensor - nothing happened in that the glass was still dimmed by virtue of the rear sensor being covered.

My concern is that my guess is that the glass should dim from either the front OR rear sensor's having light on them? Logic dictates that you'd want the mirror to dim when a clown drives up behind you with their main beams on, and for the mirror to react and dim accordingly - with my initial test - it doesn't do this....

I can't quite get my head around why you'd want the mirror to dim when a car coming towards you with main-beams on would make the mirror dim, after all, you wouldn't be looking in the mirror!

Am I missing something, or does it sound like the front sensor isn't working properly - and that only one out of the two sensors works as it should - or am i using / testing it incorrectly?

Thanks muchly for any guidance / input....
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M
The rear sensor is to sense when it is dark so the mirror only dims at night.
Cover front sensor (back of mirror) and shine light into rear sensor mirror should dim, turn off light (front still covered) and mirror will clear.
If when reversing and you have light behind you, you can press button to stop mirror dimming while reversing
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R
Thanks Maneki - but I'm now confused. For clarity, I'm going to call the sensors FRONT (mirror side), and REAR (plastic side) - as you look at the mirror from the drivers seat.

As mentioned above:

Then I pressed the AUTO button in, so that it clicked down.
Again, shone a focussed beam onto the light sensor on the FRONT sensor - nothing happened. Then, I tried covering the light sensor on the REAR - this time, the glass dimmed nicely and went dark. Then thirdly tried shining a light on the FRONT (glass) sensor whilst still covering the REAR sensor - nothing happened in that the glass was still dimmed by virtue of the rear sensor being covered.

I don't understand how the FRONT sensor (mirror side) can be the one to sense whether it's dark or not - and that the mirror dims when light hits the REAR (plastic side) - surely it would be other way round? Surely, you'd want the mirror to dim when a car with their high beams on, approaches from behind your car, and the light hits the FRONT (mirror side) sensor?

Or am I completely mad?
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M
F%$£ me, now im getting confused lol

The sensor on the plastic side is for detecting night and day.
The mirror will only dim at night. (plastic sensor detecting no light)
With plastic side sensor covered and no bright light on glass sensor it will stay clear.
With plastic sensor covered and glass sensor detecting a bright light it will dim until bright light is removed.
e.g at night when a car comes up behind you the glass sensor will detect the other drivers lights and dim the mirror (as you would have on a manual mirror with the lever)
when there is no car behind you it will return to clear so you can see further behind you.
Hope this make sense.
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R
maneki said:
With plastic side sensor covered and no bright light on glass sensor it will stay clear.
With plastic sensor covered and glass sensor detecting a bright light it will dim until bright light is removed.
Click to expand...
Right, this makes sense, and is how I'd expect it to work! However, mine does the opposite....

When I COVER the REAR sensor - the mirror dims. This is in daytime and irrespective of anything happening to the FRONT (mirror) sensor.
If I COVER the REAR sensor (and the mirror then dims), and then shine a light into the FRONT (mirror) sensor, nothing happens, as the mirror has already gone dark from the REAR sensor being covered!

I suspect that I'm answering my own question - and it seems as though this mirror isn't functioning correctly? However, will test it again this evening when it's dark to see what happens then also....
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M
Quote: When I COVER the REAR sensor - the mirror dims. This is in daytime and irrespective of anything happening to the FRONT (mirror) sensor.
The front glass is seeing day light and it thinks it night (Plastic sensor covered)
Sounds like it is working, at night it will look greenish.
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aerojon
taken from install dofit..

The rearview mirror has two sensors; one facing the front and the other facing the rear. When the front-facing sensor detects that it is dark outside, the system will be activated so that any bright light falling from behind will gradually darken the rearview mirror to reduce the brightness. As the bright light subsides, the mirror will gradually return to normal.
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B
The mirror is on when the push button is up, that is when you see the smallest part of the button. It's off when the button is down.

You will see a greenish tint on the mirror when it does kick in.
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