Octavia 2 2006 1.9ltr TDi LHD

Electronic dimming mirror.

Pleae excuse my inexperience with fora. I posted this as a reply to a dimming mirror thread but I cannot now see my post.

I have found that the dimming mirror does not operate well enough in urban, lit areas; I still get dazzled by cars behind.

The mirror operates by comparing the light received by the front-facing sensor on the mirror with that at the back. If more light hits the rear-facing sensor, the mirror dims. In well lit areas the light falling on the front-facing sensor prevents the dimming action. Headlights of vehicles coming towards also slow or stop the dimming action.

I have just tried an experiment to improve the performance. I cut 4cm of thin wall 15mm garden water pipe at an angle of about 20 or 30 degrees and attached it over the light-sensor at the back of the mirror (facing the screen), with bluetac, angled towards the near side. This made an immediate improvement, perhaps too much as the mirror is now fully dimmed in lit urban areas, with or without headlights behind. Out in the country a distant pair of headlights quickly turns the mirror green, as the lights approach. I shall try shortening the tube to tune the performance.

Why not just stick some mgic tape over it to cut out some of the front light - like a filter

I didn't realise the front one took a comparison to adjust the dimming. Btw the position of the rear middle head rest can cause problems.

Tube gives better directional control of incident light,

Tube gives better directional control of incident light,

There surely must be a more elegant way of increasing sensitivity to rear lights (which I agree is sub-optimal). If the issue is the balance between fore and aft light sensors, could a few stick-on dots in the right place do the trick?

The angle of the mirror (for the driver) has an effect too.

Always works better for SWMBO than me as she's a short ****

The sensors are evidently very sensitive. I found putting a finger over the front-facing one failed to do anything; either the sensor is extremly sensitive to ligh passing through the finger or it is infra-red sensitive. Placing a really opaque object over the sensor immediately dims the mirror. The rearwards facing sensor must also be amazingly sensitive because the amount of energy falling on it from distant headlights must be infinitessimal. Being more concerned with performance than looks, I can put up with the black tube!