Mechanical Brake Light Switch - An Alternaive Solution

[nismo1534]

I've always had issues with the hydraulic brake light switch that came installed from the factory on my AA3. From day 1 the switch was not sensitive enough. I could come to a slow stop and even hold the Atom on a slight incline without the switch triggering the brake lights. After some spirited canyon runs last summer, the switch decided to give out completely and I was without brake lights. I take my Atom out on the street, so this was not good.

After reading the post below, I wanted to head in the same direction and install a mechanical switch to trigger the brake lights.

https://www.arielatomchat.com/forums...html#post14319

The roller switch was a good idea, but I wanted something purpose-built, readily available, and easily adjustable. I decided to use an actual brake light switch you'd find on a normal vehicle. I found one that utilized a durable metal body and came with spade connectors, just like the factory unit:

https://www.amazon.com/Beck-Arnley-2.../dp/B000CRZEZ2

https://www.rockauto.com/en/parts/be...t+switch,10474



I now had to figure out a way to mount it. The goal was to come up with something simple, easy to make, and I didn't want to remove anything from the Atom or take anything apart. After looking things over, I noticed some empty, threaded holes on top of the master cylinder assembly.





The hole directly over the brake pedal would be my mount point. I used a 1/4-20 threaded screw to match the threads on the master cylinder.



I also grabbed a 1/4" x 1" aluminum bar to use as the bracket. This will hold the brake light switch.



I cut the bar to length and started bending. Once the bar went where I wanted it to go, I drilled a 1/4in hole for the mounting screw and a 25/64in hole for the brake light switch.





Here's what the completed bracket looks like, with the brake switch loosely attached.



Bracket mounted to the master cylinder assembly. Blue Loctite used on the screw threads.







Now, the wires on the brake switch are too short, so I had to cut and extend them 6in:



Heat-shrink tubing over the extensions for weatherproofing:



I had to source an additional M10-1.25 locking nut to lock the brake switch in the desired position (the switch only came with 1).



Brake light switch installed and adjusted perfectly.





The brake lights are now triggered with the slightest press of the pedal, which is completely adjustable. No more worrying about the faulty hydraulic switch. I can also keep a spare mechanical switch handy and replace it in minutes, so long as I extend the wires beforehand.

[dmc71]

Awesome job with great description and photos. Thanks!

[ivefallenandicantgetup]

Super, thanks for that writeup.

[Bravo25]

GREAT Idea! Thanks for sharing.

[cvjoint]

Clearly you're not driving hard enough. Do some hard late breaking, using the brakes like ... well ... a light switch.

Just messin'!

[2/3rdsCobra]

I had to do the same thing but I copied MadMaxAtom using a pull style switch with a spring. Here's the link https://www.arielatomchat.com/forums/thread1773.html Nice job and another option for Atom owners.

[shwagon]

Great write up and solution!

[Napalm]

Great thread. I also dislike the pressure required to set off the brake light.

[timcking]

Yeah, I had the same problem and the OEM switch finally completely failed. I didn't want to mess with bleeding the brakes so fabricated a bracket like this. Great job with instructions.