Having owned a Mk4 R in the past I really missed having complete control over the flapper via a switch. I did lots of searching and absolutely no one had done a flapper switch on the Mk5 R.
My exhaust is "tampavw" modded and while it sounds incredible I sometimes like things nice and quiet on my hilly commute to work, so after seeing no one having installed or even attempt doing a flapper switch I thought it would never happen. Since I had a switch on my Mk 4 R I figured that it had to be possible on this R.
Out came the wiring diagrams. After some searching the wire that ultimately controls the flapper was found, but we had no idea where the wire was running so I had to turn to the Vortex for help, and you guys came through for me. A couple of you posted pictures of the vacuum res that I was trying to locate and from there the wire was found hiding away in the driver side corner of the hatch.
Now I'm sure this wire runs all the way up to the ECU but I did not feel like taking apart a large amount of the interior to track it so I just ran the flapper control wires to the hatch instead.
Let's get started
First you need to access the flapper wires which are located in the hatch, drivers side. You need to pull the carpet away from the body of the car to access the wires.
Remove 3 of the plastic push button things holding the carpet in:
The next two are behind the plastic trim which just pops off with a bit of force.
This last one is all the way at the bottom, right above the floor of the trunk
After you have removed those 3 things then you can pull the carpet down. Keep in mind you can't remove it but this will give you enough room to work.
The wires that we are working with are:
brown/lilac - flapper solenoid control wire
blue/red - flapper solenoid power wire
In the corner of the hatch you will see a rubber grommet where the two wires are coming through, they are conveniently taped together. There are a bunch of other wires and all of them are wrapped in black tape, you will have to cut this tape in order to gain access to the flapper wires.
I unwrapped a bunch of the tape so it was easier to work with the 2 flapper wires.
If you want a 2 setting switch read the following:
A 2 setting switch will provide you with flapper always closed and flapper always open. In the end I went with this instead of the 3 way switch, just because I made the button look OEM.
The wiring is completely different for a 2 setting switch. If you go this route you will just make your own kit.
You will need an on/off switch, 1k ohm 1/2 watt resistor, 1 wire tap, some 16g wire and either quick connect wire fittings or solder everything.
Here is my awesome paint diagram that I made to follow for installing a 2 way switch (thanks to fred340 for the original diagram, I just prettied it up.
For the 2 way switch here is what you do:
1. Cut both the flapper wires, brown/lilac and blue/red.
2. The brown wire coming through the rubber grommet ground to chassis. There is a bolt holding the taillight assembly in that works perfect (scratch off some of the paint)
3. The blue/red wire coming through the rubber grommet attach your 16g wire to and run through the cabin and connect to switch
4. Since you cut both flapper wires you are left with the brown and red going up to the front of the car. You need to connect these wires to each other, but you need to put the 1k ohm 1/2 watt resistor in line (so you don't throw any CEL's.
5. Now you need 12v switch power and you can grab this from the cig light. Run a second wire from the switch and tap into the black/red wire coming from the cig light.
Here is a gif showing the two different states of my current switch. Talk about OEM+