auto dimming rear view mirror - how do you know it works?

[KiwiME]

Thanks for the write-up, DV52. I've tried covering the front sensor and shining an LED light on the mirror-side sensor and nothing obvious happens (w/ ignition on.) I think I'll check the fuse first (53 under the dash, if I'm not mistaken) and then drive down to the local VW dealer and ask them if I can compare it to the same model Cross Polo they have on their lot.

[brad]

Wouldn't it be easier to just ask them to show you how it works? If they can't show you then it's obviously broken & a warranty issue.

[KiwiME]

Visited the VW dealer and my car and their car performed exactly the same. The effect is subtle (at least in daylight) but it definitely works. That's a relief since I would dread taking the car in for repair. The reason I didn't notice it in my tests in the garage is because the headlights were not "on" - a rather obvious point in hindsight.

Noting that the rear sensor is at the top of the mirror, the last time I was driving at night I noticed that headlights some ways back are shaded by the top of the rear window and that shadow darkens the area over the sensor. I wonder if that's why I don't see it changing? Is the sensor on the older type mirror at the top or bottom?

There is very little traffic at night where I live so I don't get many chances to try it out.

[DV52]

Visited the VW dealer and my car and their car performed exactly the same. The effect is subtle (at least in daylight) but it definitely works. That's a relief since I would dread taking the car in for repair. The reason I didn't notice it in my tests in the garage is because the headlights were not "on" - a rather obvious point in hindsight.

Noting that the rear sensor is at the top of the mirror, the last time I was driving at night I noticed that headlights some ways back are shaded by the top of the rear window and that shadow darkens the area over the sensor. I wonder if that's why I don't see it changing? Is the sensor on the older type mirror at the top or bottom?

There is very little traffic at night where I live so I don't get many chances to try it out.

KiwiME: Sounds like success- well done!! Your model car is different from both my Golf and my Polo 6R in that the auto-dimming function on both my cars is not dependent on the light switch position (I just checked my Polo before writing this post).

Whilst I understand your logic in having tis way, on my cars the auto-dim will happen as long as the ignition is on (i.e. the anti-dazzle mirror must be supplied by a "terminal 15" fuse position) I'll look-up the wiring diagram to confirm this.

[KiwiME]

Is the sensor on the older type mirror at the top or bottom?

I'm not concerned about the headlights having to be on since they will be, only the above question.
Thx

[DV52]

I'm not concerned about the headlights having to be on since they will be, only the above question.
Thx

KiwiME: The anti-dazzle mirror in my Polo looks just like the unit in the pic below. Rear sensor on the bottom RHS (you can just see the button on the bottom of the housing in the pic)

[KiwiME]

Awesome, thanks for the photo. The rear sensor on mine is near the top-centre of the glass. I'll have to check next time I'm out at night but I think they've made an error by moving it to the top.

[KiwiME]

I see on the 'net a number of reports of this feature not working well when you have tinted windows or factory "privacy glass." My Polo has this as a standard feature on the rear and rear-side windows.

There must be new Polo owners out there with this newer model mirror? It may not be a Gentex like the one in DV52's photo above, as I can't find this one on their web site.

If this continues to be a problem for me I'm perfectly willing to disassemble the mirror and see if I can modify the electronics to bias the darkening further.

[DV52]

I see on the 'net a number of reports of this feature not working well when you have tinted windows or factory "privacy glass." My Polo has this as a standard feature on the rear and rear-side windows.

There must be new Polo owners out there with this newer model mirror? It may not be a Gentex like the one in DV52's photo above, as I can't find this one on their web site.

If this continues to be a problem for me I'm perfectly willing to disassemble the mirror and see if I can modify the electronics to bias the darkening further.

kiwiME: have you seen the circuit board in one of these units? I've taken the pic below from a google search. I'm by no means an electronics expert, but I kid myself that I know my way around a soldering iron and surface mount components. But it looks like a daunting task to me (especially without a circuit diagram as a guide)!



But if you do manage to figure out how to modify the sensitivity, then I would be very interested in hearing about your findings!

My suggestion is that you first try the "low tech" solution by placing multiple pieces of translucent sticky tape over the front sensor. If placing your finger over the front sensor doesn't make the mirror dim to its max level, then I suspect that you have other problems. If the mirror does dim, then it's just a matter of finding the correct amount of translucent material to cover the front sensor. Yes, I agree that it's not as sexy as the "pull-the-mirror-apart-and-figure-out-an -electronic-solution method, but it's an easy first try method IMO.

[KiwiME]

... If placing your finger over the front sensor doesn't make the mirror dim to its max level, then I suspect that you have other problems. If the mirror does dim, then it's just a matter of finding the correct amount of translucent material to cover the front sensor. ...

Yeah, it's plenty dark at night here and I think it's not an issue with the front sensor, more that the incident light from cars following some distance behind is not sufficient to dim the mirror much after being attenuated by the rear window tint.
I need to get more experience with it before I decide what to do.

[Splashalot]

If this continues to be a problem for me I'm perfectly willing to disassemble the mirror and see if I can modify the electronics to bias the darkening further.

I wonder if the degree of darkening in these auto mirrors can be tweaked via VDCS (Vagcom)?

[JonW]

I also think this feature in my 6R isnt the best. I often have to move the mirror 'old skool' style as the lights behind are so bright. I dont have any tints and its always been like that, but it does work as Ive seen it dim when it wants, I think the front sensor trick is the fix here and will be taping it today and report back. Wish Id seen this thread earlier, Ive been on the verge of moaning to the dealer about it as a warranty fix for the longest time, I just never remembered when I was there.