Finding Reverse light negative on Audi A3 and how to wire?

[Dams22]

I'm trying to install a reverse camera and have a couple questions about the electrics as I've never installed anything into the electrics of a car before.

1. Which wires are the reverse light negative and reversing light negative +12V on my Audi A3? I've uploaded an image of the reverse light cables, if anyone knows off the top of their head by doing a similar install would be great help as I've not got an electrical tester; although, if needs be I will go and buy one as last resort.

2. Once I locate the cable, how would I connect the reverse camera cables to the reverse light cables. Is it a matter of cutting the reverse light cables and then making a three way split with some electrical tape around it? Or would I need to get T-Tap wire terminals and crimp tool?

 

[BillyGiann]

Checking the aftermarket parking sensors of my 2015 hatchback, the +12v signal for reverse is the blue/black wire, at the left side. It is located in a loom behind the foam pad, close to a ground point (ground->brown)

 

[Dams22]

Checking the aftermarket parking sensors of my 2015 hatchback, the +12v signal for reverse is the blue/black wire, at the left side. It is located in a loom behind the foam pad, close to a ground point (ground->brown)

Thanks for your reply! In the end I got impatient and bought a multimeter tester in the morning. can now confirm and say that you are absolutely right. The blue/black is +12v and brown is ground.