Auto Dimming Mirror

[The_Hawk]

So my mirror seems to have stopped working in the last couple of months. There are a couple of reasons this could be...

It was flashed back to factory software a couple of months ago so it's possible that did something?

Or it's just died.

The little green light turns on but nothing ever seems to dim.

I've checked out the coding and testing parts of this guide:
rain light sensor retrofit and installation- VW DIY | VW TDI forum, Audi, Porsche, and Chevy Cruze diesel forum


My module is (and was installed): I've also tested the rain sensor and it works flawlessly.


But the light sensor data never changes regardless of if I turn it on/off (and the green light does change), cover the front sensor or shine light into the rearward facing sensor:


Does anyone have any ideas on why this wouldn't be working?

[gldgti]

If you are getting no change in sensor data, seems like that would mean the sensor is broke.... but I can't confirm that from the VCDS data you have supplied.

[The_Hawk]

I've looked at all the things I know to look at and it doesn't seem to change at all, so maybe it is really dead.

Maybe it's time to ask the experts at the next service...

Mostly for my own reference, the Part number is 5k7857511 should I need to order another one. Seems there are a bunch on eBay for $80 - $90 delivered which sould be a pretty cheap fix in VW world

[The_Hawk]

Small update.

While doing the testing last night I noticed that my dash cam was showing an error message when running on battery which went away when I started the car... VWs do seem to do strange things when the battery voltage gets low. Given I don't drive the Cab as regularly anymore I really need to hook it up to the charger more often.

So I plugged it in overnight to the CTEK and ran a recondition cycle and it was showing fully charged when I got home tonight so I figured I'd test it again and see what happens...

So I've tried logging those measuring blocks without seeing any movement... No on/off, no reading on the light sensor brightness...

But the auto dimming is now working?! Strange. I'll have to take it out and make sure it's working in the real world, but it looks like some extra voltage has it working again. In retrospect I should have put the multimeter on the battery first to get a reading, but something to keep an eye on for sure.

[d3vour3r]

isnt there a button underneath the mirror that turns it on/off
tried that?