Wiring a second switch for trunk & fuel door

[steveu812]

This isn't directly a VCDS related thing, but if I mess this up it may turn into something I'll need my VCDS to unravel.
Also, I'm too new to post in the 'Retrofit' section so I figured I'd take my chances here.

Since day one of ownership I've found the original location of the trunk and fuel door release buttons to be inconvenient enough that when I needed to tear into the console area to replace shifter bushings (...this then morphed into removal of soft-touch-coatings/repainting) so while this deep in, I figured I'd try to retrofit a second set of buttons. On fleabay I found a used set of buttons from a later S6 that included the plug and a usable pigtail of wires where they cut it from the car. A little testing indicated that two of the four wires for each switch powered the backlights and the other two closed a circuit. Looking at the wiring diags. for my car it showed the same thing so with the switches still disconnected, I shorted the respective terminals and got the trunk to unlatch and the fuel door to open.

My plan is to locate the second switch set on the driver's door side of the car somewhere so I was going to run a jumper harness from the existing switches to that location.
I want to use the correct size wire for this but I can't find this info on the wiring diags. or from 45+ minutes of searching the web.
The wires on my switch harness are really small so I suspect there's not much current in this circuit. But I really don't don't know.

Does anyone know what size those wires are?
Wiring Diagram

 

[stefdds]

A simple visualization would work along with a caliper measurement. They are most likely 1.2 or 1.5 or 2.0mm dia. wire(s).

However, if you must know the verified size per the Official wiring diagram from Audi, you can obtain a subscription Here:

Official Factory Repair Information - Ross-Tech Wiki

wiki.ross-tech.com

 

[steveu812]

Thanks - your numbers 1.2, 1.5 etc. helps alot as I'm familiar only with AWG and that only somewhat.
Looking at what's there, the wires I have to make the jumper harness and what I suspect as circuit current, my gut tells me I'll be fine, but it's always good to get more info.
Thanks

 

[Dr Sheldon]

A little testing indicated that two of the four wires for each switch powered the backlights and the other two closed a circuit. Looking at the wiring diags. for my car it showed the same thing so with the switches still disconnected, I shorted the respective terminals and got the trunk to unlatch and the fuel door to open.

 

[Derek]

If you are adding the second set of switches in parallel to the first set, be careful that it doesn't try to set the state of a wire to two different voltage levels at the same time when you operate one of the switches

For example on your diagram the rear lid switch pin 4 is switched between pin 1 and 2. Pin 4 at rest is connected to pin 2 which is shown as earth. IF pin 1 is live, a second switch wired in parallel would now set pin 4 to live with the original switch still holding the same wire to earth

Best regards
Derek

 

[Uwe]

They are most likely 1.2 or 1.5 or 2.0mm dia. wire(s).

No, these are signals, and likely smaller. 2.0mm dia approximately 12 AWG! Even 1.2 is somewhere between 16 and 17 AWG.

FWIW, I'm pretty sure the wire sizes shown in VAG's factory wiring diagrams are cross-sectional area in mm, not diameter.

For signals like this, something like 18 or even 20 AWG is fine.

-Uwe-

 

[SaVAGeSoot]

are cross-sectional area in mm, not diameter.

12. Wire cross section size (in mm2) and wire colors