JimVonBaden

My rearview mirror day/night switch on my A3 failed so I took advantage of the situation to convert to a automatic mirror.



Old broken switch:




Once I received the new mirror I realized the issues with the swap. I needed 12V switched power and it wasn't near the mirror. I had to first find out which wires worked the night dimming feature. Then I needed to figure out where to tap the 12V, then feed the wires down the trim to the fuse box. This is more complicated on a convertible.



No power at the rain sensor:





Some trial and error helped me find the correct wires on the mirror. I had to disassemble to connector and apply 12V from a battery to find it. Ground was brown, and 12V was white. I sealed off the other wires that ran different functions, and added an 8' extension.






More trial and error to find switched 12V and I had to create a ground point.



Wires routed and mirror attached with covers and it works. I have auto-dimming and even now have a compass.



Total cost as $70 and 4 hours work. I'm liking it.

Preston33154

I have the same issue... After my '12 A5 Cab finally hit the 200,000 mile mark and the transmission was in need of replacement ... I moved to a 2016 A3 Cab. I love this little car... but I am having a few 'downgrade' withdrawals... and then the mirror day/night lever broke! AARRGGHH... and it just flops around as I drive the very un-maintained streets of Miami.

The dealer told me I had to pay $1000 for the entire assembly >>> they don't sell just the mirror! (???)

Where did you buy your mirror?

I'm rather nervous on running a wire from the very difficult to get to fuse panel... but might be worth it!

THX >>> P.

paradyne

I did this recently on a 2017 Cabriolet. You can get a wiring loom for it from numerous sellers on AliExpress for about £10. You get a used mirror from a breakers/salvage place. The loom will have the connector to plug straight in to the mirror. One wire to a ground point, one to splice into the J519 body control module T73C pin 11 which is the reverse light signal. Another fits into the back of the fusebox in an unused spot so that you can have a fused supply. And the last one connects to T12ae pin 12 on the interier light switch to cancel the dimming when any lights are switched on.