Auto Dimming Rear Mirror

[BarneyBoy]

There is a sensor on both sides of the mirror.
I expect that when the light hitting the reward facing sensor is brighter than the forward facing sensor, the mirror dims.

[Splashalot]

There is a sensor on both sides of the mirror.
I expect that when the light hitting the reward facing sensor is brighter than the forward facing sensor, the mirror dims.

Yes, there are two sensors - one measuring light received from the front of the car and another measuring light received through the mirror from following cars' headlights.

Unfortunately, there is obviously a calibration setting somewhere that is not always correct. My mirror is next to uselss - it almost never dims, and when it does, only negligibly and when following cars are almost on my bumper. To test the mirror at night I completely covered the front light sensor whilst my daughter shined a torch through the rear window. I then timed the mirror - it took 18 seconds to dim. F*cking useless. I've mentioned it to the dealer but they tell me there are no settings they can adjust for the mirror!

Consequently, I've covered the front sensor with 2 layers of window tint film to trick the mirror into thinking light received from the rear is comparatively brighter than light from the front. This has worked to a minor extent. However, I'm still driving around blinded constantly at night.

I'd really rather a simple day/night mirror switchable via a lever. I've never, ever, in 20+ years of driving had an issue with one of those.

Ah, that's progress for you.

[Logzy]

Consequently, I've covered the front sensor with 2 layers of window tint film to trick the mirror into thinking light received from the rear is comparatively brighter than light from the front. This has worked to a minor extent.

Try some black electrical tape or more tint and see what it does.
Not the preferred solution i know, but worth a try to see what happens.

[maca]

I'd really rather a simple day/night mirror switchable via a lever. I've never, ever, in 20+ years of driving had an issue with one of those.

x2.
Technology only makes our life easier if it works.

[Splashalot]

Try some black electrical tape or more tint and see what it does.
Not the preferred solution i know, but worth a try to see what happens.

I might be wrong, but I think that would "tint" the mirror permanently - and as I reverse down a steep winding driveway I need the mirror in un-tinted mode to see where I'm going at night. Shall try it and see, though. Thanks.

Tis is real bugger - will pursue the dealer further on this, as obviously some people's mirrors work perfectly. Otherwise I'll have to try to track down someone with a vagcom in Hobart - I vagually recall reading somewhere mirror tint sensitivity is vagcom-able.

[Logzy]

I vagually recall reading somewhere mirror tint sensitivity is vagcom-able.

I dont think it is

[Maverick]

I might be wrong, but I think that would "tint" the mirror permanently - and as I reverse down a steep winding driveway I need the mirror in un-tinted mode to see where I'm going at night. Shall try it and see, though. Thanks.

The mirror will only tint when there is light shining on the sensor on the front of the mirror (facing you).

I vagually recall reading somewhere mirror tint sensitivity is vagcom-able.

The sensor for the headlights and windscreen wipers is but the mirror tint is not, it's not connected to the CANBUS and is essentially a dumb self contained unit.

[Fanaki]

Update:

before i left work i covered the outside facing sensor waited for the mirror to dim and then once dim, i covered the sensor facing me (whilst still covering the other sensor) and waited for the mirror to go back to normal. i did this a couple of times to ensure the mirror and sensors did their job.

whilst there, i readjusted the mirror so the inside sensor had a clearer line of sight thru to the rear of the vehicle. on the way home, the mirror seemed to work "normal" both dimming and un-dimming as it should.

it's working now, so beats me what the problem is...

[acdcfan]

Update:
it's working now, so beats me what the problem is...

I kow it is called technology
Mine works fine from day one.

[ox518]

I got the same problem as yours.

I have tested today under sunshine. when I put my finger at back sensor (facing windscreen), the mirror does dim. However, if I covered my finger at front sensor (facing me), the mirror seems does not dim. Is that normal?

[Splashalot]

I got the same problem as yours.

I have tested today under sunshine. when I put my finger at back sensor (facing windscreen), the mirror does dim. However, if I covered my finger at front sensor (facing me), the mirror seems does not dim. Is that normal?

Yep, that's normal.

I've given up on mine and completely blocked all light from entering the front sensor with black electricians tape. This permanently dims the mirror. If I want it clear, I just press the button on the mirror's underside to de-activate the sensors and it goes completely clear. Thus is operates like a normal, switchable day/night mirror. At least I can drive at night now without being continually blinded by cars behind.

[graeme86]

This non dimming was a problem on Mk IV R32 with large rear centre headrest.
It blocked the light going to the rear sensor on mirror from following cars, so the mirror did not dim..although you get blinded by headlights in rear view glass.

If you take out rear centre headrest then the mirror dims properly.

I now have a retrimmed Polo rear headrest and it works perfectly because there is now a clear line of site to the rear sensor.

[ox518]

This non dimming was a problem on Mk IV R32 with large rear centre headrest.
It blocked the light going to the rear sensor on mirror from following cars, so the mirror did not dim..although you get blinded by headlights in rear view glass.

If you take out rear centre headrest then the mirror dims properly.

I now have a retrimmed Polo rear headrest and it works perfectly because there is now a clear line of site to the rear sensor.

Very good suggestion, my rear headrest are up and might block the light.

[bdl]

do people leave their button pressed down (ie. green light) all the time, or only turn it on at night?

bdl

[Splashalot]

If you take out rear centre headrest then the mirror dims properly.

I now have a retrimmed Polo rear headrest and it works perfectly because there is now a clear line of site to the rear sensor.

Just tried to remove the centre rear headrest on my Mk5 - no can do - it's fixed. Not even height adjustable. Guess I'll just stick with the black tape over the sensor trick.