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Discussion Starter · #1 ·
Hi dear community!

I'm owning a F3 675 (2016) and having a problem with my rear brake light for a while.
When the Bike is cold, everything is ok. I touch the rear brake and die brake light will go on.
But after a short time of riding, when the rear brake cylinder gets hot because of the engine heat - this thing starts to malfunction.

The rear brake does still work normaly, but the rear brake light is always on "brake"!
So the car or rider behind me can't see when I'm braking.
On a public roads this feels strange as you might can imagine :/

Has anyone of you experienced such a problem or have heard of it? Or maybe even have a solution?

Have a great Easter ! Even if we have to stay at home at the times :D
PEACE!
 

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The brake light is pressure activated with a switch in the fluid path? or a mechanical switch attached by spring to the pedal?
I suspect it is fluid pressure activated, and your brake system needs to be flushed and bled with fresh fluid. A tricky process with the ABS system. There is a service bulletin outlining the procedure. A bit of search in the forum will reveal some answers.
 

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The rear brakelight switch is, in fact, hydraulic:
477091
 

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Because the OP says the rear braking action is normal, when the brake light is stuck on.
My guess would be the switch is simply malfunctioning.
 

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Discussion Starter · #5 ·
Thank you for your responses! I will flush the system tomorrow and have a look. I really do not hope that the sensor is broken due the fact it is so hard to get spareparts :/
 

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Thank you for your responses! I will flush the system tomorrow and have a look. I really do not hope that the sensor is broken due the fact it is so hard to get spareparts :/
I have a brand new MV sensor available. I bought it thinking I had an issue, but turns out I didn't so never used it.

If interested PM me, just keep in mind that you wont get anything for minimum one month as my country is on lockdown and shipping in the next month is beyond expensive ( as passenger flights were also previously used for cargo - currently not happening).
 

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Discussion Starter · #7 ·
I have a brand new MV sensor available. I bought it thinking I had an issue, but turns out I didn't so never used it.

If interested PM me, just keep in mind that you wont get anything for minimum one month as my country is on lockdown and shipping in the next month is beyond expensive ( as passenger flights were also previously used for cargo - currently not happening).
Hey thank you thats really really kind of you :) i will PM you when there is absolutely no solution :) i will bleed the whole system as good as possible.
Just thinking about it - if there is air within the cylinder - when the cylinder gets hot the air expands way more than liquid - so the pressure within the cylinder rises and the sensor will activate. So maybe (just thinking about it) thats the reason for this malfunction.

As esqz'me writes :) lets see :D
 

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Hey thank you thats really really kind of you :) i will PM you when there is absolutely no solution :) i will bleed the whole system as good as possible.
Just thinking about it - if there is air within the cylinder - when the cylinder gets hot the air expands way more than liquid - so the pressure within the cylinder rises and the sensor will activate. So maybe (just thinking about it) thats the reason for this malfunction.

As esqz'me writes :) lets see :D
That solved my issue also, hence why I have a brand new sensor. Good luck!
 

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Discussion Starter · #9 ·
Hi, bleeding the system did not work. But then i wrapped the cylinder with >> heat protection tape << - made a testride - and now the thing seems to work properly. It will need more testing but for now it's fine :)
 
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