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Rear Brake light switch question

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Micha
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Rear Brake light switch question

Post by Micha »

I currently have a universal switch installed by PO (for example: https://www.tcbroschoppers.com/products ... ght-switch) and I am toying with the idea of ​​moving to something a little more authentic. I look at what is offered today in the market (for example here at Salis: https://bmwclassicmotorcycles.com/index ... witch.html) and don't understand it all: There is a special angled lever to be mounted on the brake rod that is coupled to this brake switch. As soon as the rider activates the rear brake, that lever is pulling the inside of the switch causing contact and the current to flow. What prevents the guts of the switch from breaking down when contact is made but on the other hand the movement of the brake foot continues its entire stroke?
On the universal unit it is the spring that absorbs and contains this movement.
I apologize for the confused question, hope I explained myself well. Thanks in advance.
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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caker
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Re: Rear Brake light switch question

Post by caker »

Hi,

At rest the "switch" is engaged/pressed by the bracket, and then upon pressing the foot brake the switch is released. The two parts are not connected - they only touch each other. See photo.

IMG_2634.jpeg

Hope that helps,
-Chris

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Micha
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Re: Rear Brake light switch question

Post by Micha »

Thanks Chris.
So this switch is pressed to Normally Closed position, and as soon the leaf of the rod is not pressing it anymore, the contacts are opened to N.O. for the current to flow? :roll:
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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caker
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Re: Rear Brake light switch question

Post by caker »

If I have my terminology (and understanding) correct, the switch is normally closed. Pressing it opens / cuts the circuit.

-Chris

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wa1nca
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Re: Rear Brake light switch question

Post by wa1nca »

caker wrote:
Sat Nov 19, 2022 11:24 am
If I have my terminology (and understanding) correct, the switch is normally closed. Pressing it opens / cuts the circuit.

-Chris
Chris
when brake pedal is up swi ch is open so brake ligh is off
when brake pedal is moved downward brake swi ch is closed giving power brake ligh bulb
adjus men is made b moving posis ion of brake lever on brake pedal as seen in pic
InkedIMG_2634.jpg
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
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Bob Allan
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Re: Rear Brake light switch question

Post by Bob Allan »

And for those original BMW type switches you can get a nifty rubber (flexible plastic?) cover to neaten things up.

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Micha
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Re: Rear Brake light switch question

Post by Micha »

Thank you all.
So, as I understood it - the plunger inside that switch is always pressed by the small angled lever mounted to the rod, thus preventing current to flow and activating the brake light (hence a Normally Open device) - until the brake is engaged; then the rod with that angled lever on it is moving forward, releasing the spring loaded plunger so the switch is now closing the circuit, allowing current to enlighten the rear brake light.
Am I right here?
Just want to be sure, as all the switches I know in that area on other bikes are Normally Closed items and function the other way around, so this is unique.
Michael Steinmann
R51/3 1952
Engine Nr. 529466

Seek
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Re: Rear Brake light switch question

Post by Seek »

You are correct in the function, you just get the terminology backwards. When the switch is not in the bike, resting on the table, the contacts are closed and current would flow throught the switch. Therefore it is a normally closed switch. Pressing on the plunger opens the contacts.

All other brakelight switches are usually normally open en you have to pull on the plunger to close the contacts.

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