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· Registered
2005 CTS-V
112 Posts
Discussion Starter · #1 · (Edited)
And they said it couldn't be done...

Finally got them to work!

I swapped to the eBay clear fogs on my base CTS a while back and was very happy with the look but did not like the orange daytime running lights shining all the time.
I sold the CTS and bought a V and finally got around to swapping over the clear fogs into it.
I came across the switchback LED bulbs but read that they would not work with the V's wiring. I bought the bulbs anyway and started figuring out how they would work with our cars.
It took about three hours for the whole install which included: jacking up the car, removing the wheels and fender liners, plastic skid plate, installing the clear fogs and running the wires for the new bulbs.
I went a little overboard as far as making all of my wiring connections at the light using some sort of quick-disconnects so they can be quickly removed without cutting the wires if I ever need to remove my bumper again.
It would take probably an hour and a half to two hours having the how-to and not worrying about all the quick disconnects at the fog light...

Tools needed:
wire strippers
soldering iron
heat shrink tubing/electrical tape
zip ties
20 ft or so of 18g wire
20 ft of 1/4" black wire loom
x2 1 amp diodes
x2 inline fuse holders
x2 1 amp fuses
razor knife
old metal coat hanger (for running wires through the grommet)
Spare female harness connector with at least 3 inches left on the pigtails.
(Harness needed to steal pins from. I got mine from the front signal bulbs of an Hummer H2)

The bulbs I bought:

The V only has two available wires at the turn signal. Those two are a ground and a combined DRL/signal wire. That combined wire provides a steady 12v output to keep the bulb lit for the DRL's and then pulses the same wire to provide the flash needed for the signal.
The wire colors referenced at the bulbs may be different in your car. The harness that I have pictured is the harness that came on the "eBay special" clear fog lights. This is where the multimeter comes in handy so you can test to make sure you are using the proper wires.
This is the two wire connector that came with my fog lights.
This seems backwards but the brown wire on my harness was the 12v wire for the TS/DRL's and the red wire was the ground wire.
The stock V harness has two white wires at this connector.
Technology Electronic device Wire Auto part Finger

The switchback bulbs need three wires to function properly. A ground, a steady 12 volt DRL wire and a pulsed 12v wire for the signal portion of the bulb.
What I did in the photo below was carefully de-pin the brown wire and move it to the center position of the connector. This takes the V's TS/DRL wire and lights the clear LED's.

To de-pin it you just pry up the "pin guard" in the center of the female harness. This exposes the "lock" that keeps the pins from backing out. Gently pull the lock away from the pin and pull the wire free. Remove the silicone seal in the empty slot then move the brown wire over a spot and push it into place.
Take the new pin that you removed from the spare harness (mine happened to be blue) and insert it into the vacant spot on the right that the brown wire just came from.

Your harness should now look something like this:
Wire Electrical wiring Cable Technology Electrical supply

The amber circuit in the switchback takes priority and shuts off the clear LED's any time there is 12v's applied to the amber input. This allows the existing DRL/signal wire to provide the power to the clear LED's and also pulses 12v's to it when using the signal. The pulsing 12v's is negated by the fact that you are now providing a new pulsed 12v signal to the amber input wire which triggers the amber LED's and overrides the clear output.

I started by jacking up just the front of the V. Removing both front wheels, both inner fender well liners and the plastic skid plate that protects the bottom of the engine. Then on to the wiring....

First, I needed to find another 12v signal wire in the vehicle that pulses with the signal properly.
The two wires I found using Directed Electronics wiring database (for 12v+ L & R turn signals) are located just inside the door on the left side of the dash. Remove the side cover and you will see a black connector with a tan locking latch over it. It contains roughly 30 or so wires in it.

Vehicle door Auto part Automotive lighting Vehicle Automotive exterior

Wire Electrical wiring Electrical supply Technology Electronics

The needed wires are:
Driver Side: Light Blue/White
Passenger Side: Dark Blue/White
They are in the corners of the connector. The light blue/white is a single wire and the dark blue/white has two wires going to one pin. You can use either of the two dark blue/whites since they share the same pin.
I tested the wires and the were the proper signal wires.
Next, disconnect the negative terminal on the battery.
I carefully pulled the harness loose from the underdash and released the latch so that I could extend the harness and work on it. Remove most of the tape from the wires to gain access.

Electrical wiring Wire Cable Networking cables Electronics

You do not have to do this step but I did not want any issues if there was a problem with the added lighting system or the bulb so I ran a 1 amp diode inline (with the stripe facing away from the connector towards the new bulb) and an inline fuse holder with a 1 amp fuse to protect the circuit in the vehicle.
Better safe than sorry!

Cable Wire Speaker wire Coaxial cable Technology

I soldered then taped up the two fuse holders/diodes in place and left them hanging (w/o fuses installed) while I ran the new wires out under the hood.
I just used two 16g black wires and labeled the ends L & R to avoid confusion. I found that the easiest place to run the wires was through the existing grommet that has the hood release cable running through it.
I slid my razor knife through it to open it up a little bit.
I then taped my two black wires to a coat hanger and pushed it through the grommet and found it out under the hood. Pull the coat hanger and slack from the wires.

Tire Automotive tire Auto part Technology Rim

Now you need to connect the black wires to the corresponding L & R fuse holder. I soldered everything together then neatly taped it back up.

You now have needed wires out under the hood and ready to run to the lights.
I ran the new wires and loomed them then zip-tiepd them to the hood release cable starting behind the coolant resevoir and all the way down to the drivers light. Once my connections were made on the drivers side I then ran the passenger wire under the vehicle and zipped tied it to the existing wire harness that were already ran across.

To avoid the "hyper flash" I had to use a 50 watt 6 Ohm load resistors. When wiring these in, wire them between the ground wire and the factory DRL/Signal wire that is now in the center pin of the three pin harness. This will keep the V happy with the flash pattern.
Make sure to mount them solid to a metal part of the car. They get hot at times.

Things learned:
The bulb color is listed as "xenon white". I contacted the company and asked them what light output color that was closest to and they told me 6k but they do not match the factory HID color at all. They have a slight bluish tint to them.
This bugs me a little but they two bulbs are never on at the same time because the clear LED's are for Daytime Running Lights and turn off automatically when the headlights come on.

These projector type bulbs are super bright which is awesome. You can easily see 10-15 feet in front of you in a dark area at night just off of these bulbs.
But, they only provide directional light forward so there is very minimal light actually reflecting off of the chrome reflector in the fog light housing so you can tell where the light is coming from instead of an overall uniform output.
I wouldn't mind see someone use the tower type switchbacks to see if they look any different just for curiosity purposes...


· Registered
2005 CTS-V
112 Posts
Discussion Starter · #7 ·
Thanks for the compliment! Glad to see it was useful.
The switchbacks are holding up well so far. I have not noticed any issues out of them.
They do get warm though!
However, I used some 1157 projector style bulbs they offer for my reverse lights and one of them was very dim out of the package.
When I went to pull it out to check it, I accidentally pulled the heatsink off of the housing which separated the bulb.
That's when I realized that there was a resistor inline on one of the wires inside the housing and not on the other side.
I removed the resistor then superglued the housing back together and it has been working fine since at full brightness.
Glad they helped take care of it for you. If anyone finds a better source for bulbs let us know!
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