Rear Brake Light Flashing intermittently - or so I am told

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adventuredon

adventuredon

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A rider pulled up to me on a roundabout today and said that while following me on the motorway my rear brake light was intermittently flashing/activating. Obviously I cant argue that it isn't. I am not resting my foot on the pedal, it wasn't when I was braking. Its like a loose connection. Got to work and the brake pedal moves freely, very freely. It does return to position easily under spring. It seems it is very easily activating the light. Is there an adjustment screw to lengthen distance between pedal travel and microswitch on these models? (1150R). I couldn't see as dark when getting to work and dark when getting home. Is it likely that the vibrations can allow the pedal to jump up and down to activate switch? Kinda hard to see for myself :) Ideas before cleaning and fiddling on the weekend will be appreciated (pistons move freely and have been pushed in etc to regulate non sticking - not that they have anything to do with the switch but just to shortcut some of the random incoming suggestions early..)
 
On the 1150 I think (if I remember correctly) it is a screw on the pedal assembly.
 
Don;t bother with adjusting the pedal!!!!! You can fuck up the free play on the master cylinder !! It NEEDS free Play

If you lie down beside it you will see the brake switch and the little arm that actuates the micro switch

Hold the pedal down and GENTLY bend the arm downwards at the end basically so that it makes contact earlier and has a bit of tension to gold the micro switch closed

Do it just a mm or 2 at a time so that you don;t need to stand on it to make the light work

You can test it as you do it by parking back to a door or wall with ignition but not engine running till you get the setting you want
 
First check the bulb contacts in the rear light bulb holder.

I had exactly this issue back in 2016 on my 1150, with the added bonus that it was triggering the ABS light. My mate said it was light following a mobile disco. Like you I wasn't riding the rear brake and everything seemed correctly adjusted.
Suspecting a broken bulb filament making intermittent contact, I changed to a new bulb which made no difference.
After rigourously checking that there were no broken wires, iffy switches etc. I moved on to checking the ABS servo and associated items. Nothing made any difference.
Tadgh OCuillan (probably spelt that wrong) from here suggested checking the bulb contacts in the holder and I found they were covered in black oxidised crap - like you used to get when ignition systems had points. I scraped this off, applied ACF50 to the contacts using a cotton bud and put the original bulb in. Problem solved and 5 years on I haven't touched it since.

Worth checking, hopefully you'll be as lucky as I was.

Mac
 
Mac Henderson said:
First check the bulb contacts in the rear light bulb holder.

I had exactly this issue back in 2016 on my 1150, with the added bonus that it was triggering the ABS light. My mate said it was light following a mobile disco. Like you I wasn't riding the rear brake and everything seemed correctly adjusted.
Suspecting a broken bulb filament making intermittent contact, I changed to a new bulb which made no difference.
After rigourously checking that there were no broken wires, iffy switches etc. I moved on to checking the ABS servo and associated items. Nothing made any difference.
Tadgh OCuillan (probably spelt that wrong) from here suggested checking the bulb contacts in the holder and I found they were covered in black oxidised crap - like you used to get when ignition systems had points. I scraped this off, applied ACF50 to the contacts using a cotton bud and put the original bulb in. Problem solved and 5 years on I haven't touched it since.

Worth checking, hopefully you'll be as lucky as I was.

Mac
Click to expand...

Hi. Thanks for the info but my rear light unit is the LED unit fitted. Replaced this 6 months ago so no contacts on bulb. Just a plug in from the LED board.


Sent from my iPhone using Tapatalk
 
DrFarkoff said:
See above regarding brake switch Don
Click to expand...

thanks, but I want to increase distance between peddle and activation of light, not reduce. I'll reverse your suggestion though. I suspect bumpy roads are causing pedal to move downwards and hence activate light, but yes I'll look at that Thank you. Maybe the spring is a bit tired ? PS. at this moment I have no idea if the problem will be fixed by any modification as it was only pointed out to me whilst riding...and hard to replicate stationary. It'll pass MOT as will be tested as working at stationary...but might just irritate motorists..:)
 
adventuredon said:
thanks, but I want to increase distance between peddle and activation of light,
Click to expand...

That is EXACTLY what bending the tang further downwards does!!!! I have been fixing these bikes for nigh on 20 years now Don, I do have an idea what I am talking about!!

You NEED 2mm of free play between the pedal being at rest and the rod engaging the rear master cylinder!

Don;t fuck about with it! if you don't have a clue what you are actually adjusting!! If this measurement is not there, you can be engaging the rear brake!

It is really easy to duplicate light activation!!!

Put the bike on the centre stand and push gently on the brake lever with your finger

Note where the light comes on?

If its in the first 5mm of travel? Every time you hit a bump it will activate

Bend the end of the tang down in increments until you get your magic distance that you think you want !
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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