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Tail as Turn Mod

6116 Views 4 Replies 3 Participants Last post by  Yooshaw
I recently finished installing a Diode Dynamics "Tail as Turn" module in the rear. This module combines the rear brake light and turn signal into one, essentially making the brake light do double duty as brake and turn signal. I then converted the normal rear turn signal into an extra back-up light for more illumination.

Items I used for this mod:

- Diode Dynamics "Tail as Turn" Module
- LED 921 bulb to replace the stock reverse light
- White 1156 LED bulb to be an extra back-up light
- 11 Ohm resistor (6 Ohm would work, I'll explain why this I chose 11 Ohm below)
- Wire, electrical tape, liquid tape, solder, all the stuff to make new connections

Video in action:

You can also convert the stock turn signal for whatever you want - keep it a turn, extra brake light, extra running light. Just have to do the right wiring.

No matter what, you'll have to wire in a resistor. I've determined the DD tail as turn module works in two ways. When brake is NOT applied and turn is activated, the module uses the turn signal input to power the brake lights as turn signals. If this were the only case, a load resistor would not be required as the brake lights provide enough draw to prevent hyperflash.

However, when brake is applied AND turn signal is activated, the turn signal is not used to power the brakes. Instead, the turn signal interrupts the brake signal, actually causing it to blink opposite the front turn signal (ie when the front turn is on, rear is off and vice versa). This is where a load resistor is required, as there is no load on the turn signal circuit and it will hyperflash.

This video shows that better - here I have an amber led turn signal with it wired like stock. This better shows how the tail as turn flashes opposite the stock turn signal (kind of a cool effect actually):

I chose an 11 Ohm resistor as I have determined that our cars need to see at least 1.18 amps to not hyperflash (could actually be less, but haven't found something to test yet). The 11 Ohm resistor provides 1.2 Amps. A typical 6 Ohm resistor draws 2.2 Amps - it will still work, but may overtax the wiring, especially in the case where no brakes are applied and the turn signal is powering the brake lights AND load resistor.

Comparison of stock back-up light and new back-up lights. All images had camera settings locked at f2.0, 1/20 sec and ISO 80 for valid comparison.

I can post some more details for those that may want to do this - be warned you have to cut into your stock wiring.
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Great job as usual Yooshaw, I love the mod!
Some wiring directions:

In order to have both sides of the rear combination lamp (lamp attached to body and lamp attached to trunk), you have to make an additional wire run to the lamps attached to the trunk. You can wire it up where only one side functions as the tail as turn.

For the body mounted lamp:

F29 - Driver Side
Pin 1 - Ground (Black Wire)
Pin 2 - Stop Lamp (Red Wire)
Pin 4 - Turn (Purple Wire)

F30 - Passenger Side
Pin 1 - Ground (Black Wire)
Pin 2 - Stop Lamp (Red Wire)
Pin 4 - Turn (Orange Wire)

For the trunk mounted lamp, you'll need to take some of the trunk liner off to gain access to the hinge area. Inside the driver side hinge are a bundle of wires. I intercepted the wires at this location. For the stop lamp, you'll find two red wires in the bunch. Through experimentation, I determined which red wire was for which side and wired appropriately. For the reverse wire, you'll find a white wire in the bunch. I tapped into this wire, and ran wire back to the body mounted stop lamps. For the passenger side, I ran the wire under the sill plate to conceal it.

Hope this helps


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Question: is it possible to install this module in a way that would use only the inner brake LED triangle as the turn signal? I love the look of this mod with the reflector LEDs; considering adding almost exact configuration on my white 2014 premium. Thanks for all your awesome input!
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