This DIY covers the wiring modifications only and does not cover the physical installation of the light assembly as there are other DIY's and YouTube videos for that. (I did add 1 physical mod at the end that I think you'll appreciate)
Since the Valenti 4th brake light was not designed with the US of A in mind, some alterations need to be made for it to work in the following manner:
Backup lights on when in reverse.
The --v-- light on when headlights or parking lights are on. (running light)
Triangle light on solid when braking. (4th brake light)
This will require you to open up the back of the light assembly (10 screws) and perform some soldering, so if you don't have good soldering skills, move along. I am also not responsible if you screw up your light and or void your warranty on said light...so there!
Starting at the connector end of the Valenti wiring harness you will see 4 wires. 3 go into a connector, (Green, Blue and Black) and a long red wire.
First you will need to remove the Blue wire from the center position of the connector (by cutting or releasing the pin) and extend that wire so it is the same length as the long red wire. I suggest that you solder and use shrink tube on your connection.
Now the connector is ready to be plugged into the OEM connection in the trunk which will give us our Backup lights. If you notice, there is nothing in that center position for the blue wire to have plugged into, that's why we pulled it out.
Moving to the inside of the Valenti light assembly (remove the 10 screws and pop off the back) you will find 3 small connectors. You may wish to mark them is such a way that you will get them plugged back in to each other correctly (numbering, color code, take pics, etc) or just pay careful attention to where they go.
We will now perform the following modifications:
On the triangle board, de-solder the orange/black wire(s) from the "stop" contact and also de-solder the green wire from the "TA" contact. Now solder together the orange/black wire(s) to the green wire and shrink tube it (don't forget to slide your shrink tube onto the wire BEFORE soldering...ask me how I know). This wire ultimately becomes the red wire outside of the light assembly and gets connected to the red wire (running tail light, 12V is supplied here when lights are on) at the tail light for the --v-- running light.
I then added a ground wire (black "S" shaped wire on the left side of the triangle), soldered from the "GA" contact to the contact shown in the pic below which is the anode (-) side of LED L6, doing this provides a constant return path for all LED's in the triangle, effectively bypassing the Q1 transistor (solid state switch) and the rest of the F1 blinking circuit. The red wire that's soldered to the "fog" contact ultimately becomes the blue wire outside the light assembly, which I connected to the green wire (brake, 12V supplied here when brakes are applied) on the tail light harness for triangle light brake function (no F1 flashing) regardless of whether parking light are on or not.
Note: Use caution when soldering the wire to the leg of L6 LED. As with all soldering, use only enough heat to get the wire attached and avoid overheating as you may damage the LED.
As promised, the one physical mod I did was so that future me is happy. After breaking the OEM light where the 10mm bolts screw into the push on nuts (thanks to rust), I decided to eliminate that possibility and use plastic push pins instead. You have to ream out the hole in the plastic mount to accomodate the size push pin you decide to use (the mounting point on the bumper tab is 10mm I believe)
Running Lights on only
Brake light only
Brake and Running lights on
Enjoy!
