I am always looking to "tinker" with my toys, and can't leave well enough alone! Hence the following DIY.

I completed the following project weeks ago, never had a chance to post this up, but recent questions by members PorscheCrazy and others reminded me. Maybe someone will find this useful...

This DIY covers modification to my upper third brake light wiring to alter the LED from a single constant "on" steady state to a blinking light when brakes are applied.


I actually got this idea from a member of a non-6Speedonline Porsche forum that is very popular. ;-)

I had always thought that having a blinking third brake light would be a great safety enhancement, and more so for smaller sports cars. SUV and mini-van drivers don't realize they just can't stop in the same short distance, this is for them or even those tailgaters and morons who love to ride up as close as possible to prove a point or something...

Anyways, I found a small company that produces a controller that when tapped-into your brake light wiring modify from steady to blinking. The company is Kahtec Technologies International. www.kahtec.com This US company produces several products all focused on safety modifications for brake lighting. Someone recently mentioned that there are other products out there -- I do not have any knowledge of them or experience.

I went with the Kahtec "Intelligent" product, which when added claims to flash the third brake light 6 times rapidly when first hitting the brakes, then a steady 3 blinks every 6 seconds for as long you keep your foot on the pedal.

I ordered on the Kahtec web site, and in a couple of days the small box arrived as advertised. The box contained a small wired black box with Red, Black, Blue wires, set of wire taps, and instruction sheet.


The instructions are very clear, easy to read and I felt comfortable that tapping into my wiring would be reversible should I have to switch back. So I set off in search of the best location to grab the wires in my car ('14 C4S coupe). I originally went about pulling the third brake light entirely from the rear vent grill lid (see my other DIY DIY: 991 Upper Third Brake Light Removal but after doing so, decided that there just wasn't a good location back there to mount the Kahtec black box. Also, Kahtec states that the box is NOT weather proof.

So, I recalled locating the wiring harness for the third brake light and antennae bump back when I was wiring my car for the back-up camera. I went back into the interior, passenger side under the back window... I pulled the trim off, and right in front of me was the wiring bundle I needed! It was great not to have to dig and search for wires for once!!

Here's the bundle -- there are three wires. Black/Red, Brown/White, and a larger solid black cable. The cables run from the passenger side of the car up into a rubber grommet (upper right side of pic below), which leads into the trunklid area and up to the grill where the upper third brake light resides.

For reference - in the pic below, LEFT is the passenger-side rear corner under window, RIGHT is near the Sound Symposer opening under the center of the rear window.


You'll need to slit the wrapping-tape to separate the wires...


I quickly determined that BLK/RED is power (+) and the BRWN/WHT is ground (-). The solid black cable is for SAT/NAV antennae so I didn't mess with it (hmmm.... what project might I need THAT wire for???).

With the wires separated, the next few steps are easy to follow right from the Kahtec instructions included...

Get the Kahtec black box, and the three red plastic wire taps ready. (NOTE: I've since modified the wires further. I don't like using the clamp wire taps, so I went back and replaced with soldered bullet disconnects. Much more reliable, easy to disconnect if necessary, and will maintain a much "cleaner" connection. I'll post some new pics of the modification to the connectors when I get a chance.)

• Hold the BLK/RED wire, pull it into the red wire tap.
• Take the RED wire from the Kahtec black box and push it into the red wire clamp.
• Clamp down on the red tap until you hear it "snap" and use a pair of pliers to make sure you've pushed through both wires.

• Now take hold of the BLK/RED wire about an inch away from the tap you just installed, and push the wire into another red wire tap.
• Take the BLUE wire from the Kahtec black box and push the end into the red wire tap.
• Clamp down to complete the splice connection.
• Take the third red tap, and holding the BRWN/WHT wire push it into the tap.
• Take the BLACK wire from the Kahtec box and push it into the red tap and clamp down.

The last very important step? Make sure you follow the directions, and CUT the BLK/RED wire somewhere between the first and second red taps you just added in the steps above. Doing so now causes all power to run through the Kahtec black box to the upper third brake light. If you forget this last step, your brake light will continue to function as normal, without the blinking.

If for some reason you didn't get the wiring correct, you can disconnect the taps and re-try. Try to leave as much wire length as possible in case you need to restore to original state without the module. Also, when using clamp taps, it is possible that you didn't get a clean cut through both wires -- so if you are not getting the module to work, or you get any dash warnings about "third brake light not functioning" you can start your troubleshooting with the clamps.

If you take-on this project, please post your end results and experience here for all to share!

I have a video of the brake light blinking but won't get it posted right now.

Have fun!

 

So I finally got around to this modification. One of the things I wanted was to be able to dictate how many times the brake light flashed, so I wound up with this unit. It has a very small footprint and comes with a variety of programming features including number of flashes, intensity of flashing, seconds between flashes, etc. This pic gives you an idea as to how small it is:



The wiring is the same as jawells mentions - tap into the ground wire, connect wire from the unit to the brake switch wire and brake light wire. The white wires you see are the programming wires.



I connected a momentary switch to the white wires to aid in programming the unit



Another thing I wanted to do was to have an on/off switch to the unit. There has been talk about the legality of flashers, so I connected a switch. If a cop were to stop me or I have issues during state inspection, all I have to do is flip a switch and the 3rd brake light will go back to normal (no flashes)



I was going to put the switch on the door sill by the engine cover and frunk releases, but then changed my mind. Wasn't sure how it would look, and if I made a mistake drilling the hole, would cost me over $200 to replace the sill cover. There was really no place under the dash and it seemed that the backing of the dash was metal. Did not want to drill through metal. So I just wedged the switch behind the panels on passenger seat on the driver side. Doesn't look great, but it is functional and I don't see it with the seat up.



This is what is looks like under various braking. Blinks 7-8 times, then constant on. What is cool is that I can change the flashing pattern whenever I want.

3rd%20Brake%20Light%20FINAL_cut_zpsxvgovfvf.mp4

 

Have you been rear-ended?

 

Not in Porsche, but in other cars. And I know others who have. I get tailgated in Porsche a lot.

 

i was driving behind a new hyundai genesis last night and noticed when the drive braked the 3rd brake light flashed three times then goes to fixed illumination until brake pedal is released. definitely got my attention.

 

Yep, I just purchased the Kahtec unit, going to install it this weekend.. Based on Jewells great tutorial looks like it will just take a few minutes.. I already figured out how to access the cabling as a side effect of the rear camera installation. It is really easy to get at, and Jewells already figured out the wiring...

There are several variants of the unit.. I went with the version that flashes several times and then goes constant when you hold the brake on. And won't start flashing again until you let of the brake for at least 8 seconds.

I also found another unit as well that is programmable and has something like 19 different modes. All of them are relatively cheap so I may experiment with that one as well.

I've seen several cars with this capability lately.. I suppose there is a small risk of getting stopped by a cop for this. So I may put the switch in as well, but it's just a fixit ticket around here. But it is a risk that I think is well worth it.

I've been rear ended a couple of times in stop and go traffic. I find myself always pumping the brakes anyway in many other situations just out of concern... If nothing else it helps gets the attention of the morons who are texting..

 

Yes, I forgot to thank jawells for his excellent post, inspiration, and help no only with this modulator post, but all his other DIY posts as well.

Thanks jawells!

 

Great stuff, guys.

As I've said before, I'd be interested in this mod if there was a way to enable the flashing light feature only after a certain amount of brake pressure is applied (say, 50%). I feel like a hard-brake situation would definitely warrant such a flash.

Regardless, cool stuff. One of you should put a video up!

 

Yeah the brake pressure thing would be pretty useful... I haven't really looked at the 991 brake system... But from my schematics I don't believe there is any sensors available in that realm (brake pressure) that could be exploited for that purpose.

A bit more manual approach might be to have the enable/disable switch a bit more handy and somehow mounted in the console (or using one of the console button hacks). Then you could activate/deactivate based on driving condition. But that is definitely not ideal and probably not worth the hassle.

 

I did post video of the way the flasher works. It is on the very bottom of my post -- the small box. Don't know why it pasted like it did

 

Love the chirping bird

 

Great job PorscheCrazy!! Like the switch you've added. Nice to see mods to make mods even better!

Happy Motoring!

 

I thought our cars did something similar to this from the factory under hard braking ... It is not quite the same thing as the 3rd brake light flashing each time (which btw I think is a great idea).

I got this impression when Motorweek did their first test on the 991 they show them braking hard and all of the brake lights flash.

Here is a link to the test, look around the 1:42 time frame.

http://www.motorweek.org/reviews/roa...12_porsche_911

 

I don't think so. What you are seeing in the video is an effect caused by the light emission frequency of the LEDs and frame capture rate of the camera. Someone else on this board is probably much more knowledgeable about this than I am so I may be wrong of course.

 

Outside of North America, German marques do blink the rear lights as a warning sign that there is intense braking being applied to the car. It is activated by a monitored and measured deceleration rate. BMW's do this too. NHTSA does not allow this option to be activated in the states. People in the US with BMW programming software and cables have learned how to reactivate this feature through S/W tweaks.

In BMW-land there are many changes that can be made to reactivate features and control functionality that is not normally allowed. I wish we could find the same type of S/W for our Porsches. Window control, locking options, light controls, belt warnings, getting rid of NAV acknowledgments, etc would be just a quick options update away.