3rd Brake Flasher

Mazda Miata is a very small car and sometimes drivers following in bigger cars might not notice right away if you are starting to brake.  To alert their attention, a flashing 3rd brake seems like a good solution. 
There are many modules available on the market; for example, the GS-100A, sold under multiple brands and are very inexpensive. Installation of such devices is simple but requires you to cut the wire from the 3rd brake and attach it to the hanging wires on the flasher module.

I was able to source the same type of connectors as Mazda used for the 3rd brake connection and made a simple kit, which simplifies installation to a plug-n-play type.
DSC_8758The installation does not require to remove any panels.


This module will produce a strobe effect for a couple of seconds, flash a few times,  then stay solid afterward. For sure this will be very noticeable to drivers behind, but I think it will also be very annoying during stop-n-go traffic.

I designed my own version with an integrated accelerometer. It will flash only during hard braking when deceleration exceeds some threshold.

The picture below shows the first prototype.


To test this version to find an optimal threshold, I installed this device inside the cabin and connected an LED strip for visual control. Power comes from the brake light wire, so I have a perfect simulation.


The legality of such devices is not very clear, and different for each state. For California, it is legal to produce 4 flashes during the first 4 seconds of brake application. My current implementation will blink 4 times, with a 400ms period for each blink, when the accelerometer detects force -0.6G in any direction.

To simplify installation, I have implemented the detection of deacceleration in all directions. Whichever exceeds the threshold, will initiate blinking.  The picture below shows the final design.





One more discovery was that the Mazda MX-5 RF model uses a different type of connectors for the 3rd brake light. Fortunately, I was able to source these connectors as well.




Both versions now available through my store

Unfortunately, Fiat 124 Spider uses slightly different connectors, the search continues.

Discussion on Miata.net forum.

10 thoughts on “3rd Brake Flasher

  1. Please pass onto RF owners that the connection is accessible by partially opening the roof and looking on the driver’s side, same panel as the light. Otherwise it works great, and was a simple install once I found that the connection was not in the trunk.


  2. Installed this about a week ago… works great. Didn’t get the accelerator version, I think being able to apply my brakes even when stopped and having the flash to alert the car behind me is a better solution.


  3. A great unit that may save your back bumper or maybe even your life!
    Many thanks to Edgar Morley regarding the location of the connectors on the RF.
    After just installing it on my RF, I found it quite easy to do, however it is a little bit fiddly as you’re working pretty much up-side-down between two sections of the roof and you want to make the whole lot as compact as possible to avoid it hitting the middle-roof section when it’s fully open.
    Further I have a suggestion, seeing Mazda has gone to some extra trouble by using moisture resistant connectors on the RF, I thought that it would also be applicable for the 3rd brake light flasher electronics. So I chose to make sure that the heat shrink tube was totally sealed at both ends by applying a few drops of contact glue, just to be sure.


  4. Pingback: 3rd Brake Flasher – Part 2 | Gadgets for my MX-5 2016 (ND)

  5. Pingback: 3rd Brake Flasher – Part 2 | Gadgets for my MX-5 2016 (ND)

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