Tuesday, August 6, 2013

Wiring up the DIY Rear Diffuser LED

Continuing from my last diffuser post - the final step in the BNR34 rear diffuser project was to wire up the LED. So this is how I did it:

The LED unit itself has 3 leads coming out of it, labeled+- and brake.  The unit was described as having aflashing brake lamp a la F1 style, and my 12 volt tester confirmed this was the case.

In any case, the first step was to ensure that, should I have to remove the diffuser in the future, I would be able to disconnect the leads without having to cut any wires. So, I found and ordered 3 lead to 3 lead connectors, which I then soldered onto the ends of the wires coming out of the LED, as well as to 3 wires leading into the body of the car.

It ended up looking like this:
See the white connectors
Next, with the wires being exposed to the elements, I wrapped electrical tape around the leads, and also used some protective heat shrink tubing for the LED leads going all the way into the body.  There is a rubber grommet (which has other wires going through it too - most notably the back-up camera leads) covering a hole just above the license plate frame, so I passed the wiring and the heat shrink through this.

I then removed the rear seats, ran the wiring alongside other wiring, zip-tying strategically, and then routed the wire to underneath the center console.  I soldered on some connectors (one side the wires from the trunk, the other on the wire leads going to the switch), to allow for complete removal of the center console when necessary, and then ran the connecting wiring through the pre-existing hole that I had drilled for the ATTESA controller that never worked right for me. I made sure I used connectors, so if I ever need to remove the console, I don't have to cut any of these wires.

On the trunk side, because the wiring into the car ran on the left side, I opened up the rear left side light cover to access the wiring there.  I then cut two short pieces of wire, and soldered the ends of both to a two lead connector.  On the other end, I soldered one wire onto the lead for the running lamps (there was already two wires soldered together on the factory harness for the two left rear lights, so I simply soldered on top of that, rewrapping in electrical tape), and then used a tap for the other wire, which I connected to the brake light wire.  This two lead connector was then attached to the two lead connector for the two wires coming BACK from the main cabin. So now I had one long connection going from the bulbs to the center console. I used clips throughout, in case in the future I want to remove part of the circuit but keep other parts, with no cutting required.

For the lead coming from the LED unit, I soldered a connector to the ground wire and bolted it to the body. The remaining two wires - one being the positive lead for the running lamps and the other for the brakes - I ended up also soldering leads for connectors, to be mated to the appropriate connector for the wires leading to the main cabin area. So this was the other long connection, going from the LED to the center console.

So, I now had a complete (fairly long) circuit, broken only by a lack of a switch connecting the two leads coming INTO the cabin from the LED unit itself, and the two lead going OUT into the cabin to be wired into the brake light circuit.   Initially I had envisioned have one switch handling the ground wire only and serving as a master on/off switch, but then realized that I wanted independent control of the braking and the running lamp circuits, as the flashing red lamp clearly violates Japans shaken (road-worthiness) laws.Thus I ended up sending 4 wires into the cabin (2 in, 2 out).
Here is the harness I made, open leads (4) to connect to the switch, the clip inserts into its mate underneath the center console
Given the need to be able to quickly toggle the LED on/off from within the cabin itself (i.e. remember this mod likely is illegal on public roads), I spent some time looking for various switches which would work. Initially, I was set to use these tiny switches, with one switch being for LED to come on with the running lights, the other switch being for the LED to be wired into the brake circuit.  

The problem, however, was that I now had the problem of how to affix these switches to the center console.  Do I carve out two holes directly? Or do I have some kind of bracket? Where would I locate them? Should they be visible? Or do I install in a hidden spot?

In the end, I finally decided that something that looked or was, OEM would be my best bet.
I found this on Yahoo Auctions - it is the switch for the OEM Nissan optional foglights,
as our
 red R33 friend Miyuki-san demonstrated
But rather than placing this switch next to the GT-R logo where it is normally placed:

I decided to continue with the stealthy scheme and install inside the console.  So this required some cutting of the center console for the switch to fit.
The center console, as seen from below - I had to use a drill and drill several holes
as the angle was wrong for the Dremel!
And then use a very sharp razor knife to make nice and clean
Then, I discovered that while the switch fit perfectly, the switch itself was too tall, meaning I had to cut off some of the bottom of the switch, and also bend the leads on the wires so they could connect to the switch with minimal amount of wiring sticking out of the bottom vertically, where it was bumping into the G-sensor.

Used the Dremel here!

Note how the leads are bent 90 degrees
The end result, however, looks fantastic, is solidly mounted and is hidden.
Actually it looks here like it's lifting up a bit, but in reality the switch is flush
with the floor of the console box
Anyway, it all works perfectly in the end - here is a video showing the LED lamp in action: First, just the running lamps, then turning the switch on to get the running lamps plus the LED, then the brakes with the LED (see how it flashes), then release the brakes, then turn off the LED.

So now all that's left to do is see how the diffuser performs at speed...

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