Rear bulb warning / failure

[gb's]

Hi looking for some advice here, this must have happened to someone else!
2004 r1200 gs with servo and ABS.
Orange warning triangle and rear bulb icon displayed.
Bulb is still showing rear and brake lights but only using one filament, the system is doing its job of reducing the power to the rear light filament and then increasing it when brake applied.
Have removed bulb from holder and tested, both filaments work when connected to a 12v supply.
Have tested, using a multimeter, the bulb holder, one contact shows a voltage of c5v when ignition turned on, increasing to 12v when the brake applied. The other contact shows zero or about 0.5 of a volt.
Have removed light unit to check for broken, dirty contacts but it all looks very clean and tight.

I'm a bit stuck now what to try next and would appreciate any advice.

 

[Santa-2512]

A new bulb would be the next step ( the cost is minimal)

 

[Santa-2512]

A new bulb would be the next step ( the cost is minimal)

You normally get a lampf warning - it could be a front bulb failure

Lampf is just a general warning

 

[DrFarkoff]

Hi looking for some advice here, this must have happened to someone else!
2004 r1200 gs with servo and ABS.
Orange warning triangle and rear bulb icon displayed.
Bulb is still showing rear and brake lights but only using one filament, the system is doing its job of reducing the power to the rear light filament and then increasing it when brake applied.
Have removed bulb from holder and tested, both filaments work when connected to a 12v supply.
Have tested, using a multimeter, the bulb holder, one contact shows a voltage of c5v when ignition turned on, increasing to 12v when the brake applied. The other contact shows zero or about 0.5 of a volt.
Have removed light unit to check for broken, dirty contacts but it all looks very clean and tight.

I'm a bit stuck now what to try next and would appreciate any advice.

They used to have a problem internally with corrosion at the tail lamp / tail lamp wiring

Do not use a mutltimeter Use a proper incandescent test lamp

A multimeter draws miniscule power and can show volts even when they aren;t there

The incandescent test lamp shows if the connection / supply is weak by either not illuminating or glowing dimly


power

 

[gb's]

Thanks so far, have tried a new bulb no difference. I think the comment from Dr Farkoff explains the tiny v reading from the contact that doesn't seem to be receiving power.

 

[TLSgazza]

Thanks so far, have tried a new bulb no difference. I think the comment from Dr Farkoff explains the tiny v reading from the contact that doesn't seem to be receiving power.

I had problems with a rear lamp that was heavily corroded and gummed up with road dirt a few years back. It's amazing how much dirt can get into the rear area if the back light assembly. It's a very basic design that could be a lot better. I changed my light for another one in the end and it has been fine ever since.

 

[gb's]

I had problems with a rear lamp that was heavily corroded and gummed up with road dirt a few years back. It's amazing how much dirt can get into the rear area if the back light assembly. It's a very basic design that could be a lot better. I changed my light for another one in the end and it has been fine ever since.

Thanks Gazza i've dropped the light unit down and the contacts look quite clean, want to disconnect it completely but having difficulty disconnecting the wiring block, cant seem to find the catch to let me pull it out. - fat fingers!

 

[Santa-2512]

Its normally a pinch / tab, use a small screw driver, but careful not to snap the tab off

DAMHIK - i did it on my ews ring lol

 

[iangough]

This happened to me a couple of months ago. Cleaned the rear bulb socket within an inch of its life and it still gave an error. The rear light worked. I replaced the bulb as a last resort and the error went away. Turns out that if the filament is worn, the can bus does not get the correct resistance measurement so reports an error.

Hope this helps

Sent from my Pixel 8 Pro using Tapatalk

 

[gb's]

This happened to me a couple of months ago. Cleaned the rear bulb socket within an inch of its life and it still gave an error. The rear light worked. I replaced the bulb as a last resort and the error went away. Turns out that if the filament is worn, the can bus does not get the correct resistance measurement so reports an error.

Hope this helps

Sent from my Pixel 8 Pro using Tapatalk

Thanks Ian, put a brand new bulb in today just in case but no joy.

 

[iangough]

What about the indicator builds ? Same logic applies.

Sent from my Pixel 8 Pro using Tapatalk

 

[botus]

on a K1300GT the tail lamp and stop lamp is a single filament bulb - the ZFE uses PWM (pulse width modulation) to dim down the always on stop lamp to fake a tail light, and then pushes it back to full when braking...

that's not how it works on the GS where its got a normal twin filament bulb - however the ZFE on a GS will use PWM on the brake light to fake a tail light if its bulb pops

the reason I mention is on a K1300 forum two recent posts about lamp failure - in the end had to replace the ZFE, appears it gets worn out and this PWM plays up

 

[gb's]

on a K1300GT the tail lamp and stop lamp is a single filament bulb - the ZFE uses PWM (pulse width modulation) to dim down the always on stop lamp to fake a tail light, and then pushes it back to full when braking...

that's not how it works on the GS where its got a normal twin filament bulb - however the ZFE on a GS will use PWM on the brake light to fake a tail light if its bulb pops

the reason I mention is on a K1300 forum two recent posts about lamp failure - in the end had to replace the ZFE, appears it gets worn out and this PWM plays up

Thanks, hope it's not my Zentrale Fahrzeugelektronik! (Had to Google what a ZFE was). My problem is even though both filaments in the rear bulb work the bike is treating the bulb as if the tail light is broken, using the braking filament as you describe (or it could be the other way around, I don't know which filament does which job). Disconnected the battery today in the vain hope it would shock the bike into behaving but no luck.

 

[botus]

I don't know which filament does which job). Disconnected the battery today in the vain hope it would shock the bike into behaving but no luck.

pretty sure its the tail light (nothing at the back would be dangerous all the time), unless its clever enough to fake which ever might be dead ?

bold suggests both
how it works infers only a tail lamp ?

page 115 K25 307 user manual

A warning appears in the multi-function display if a bulb is defective. If the brake or rear light fails, the symbol is accompanied by the 'General' warning light, which lights up yellow. If the rear light fails the second filament of the brake light shines at reduced brightness to double as a rear light. Even though you have this substitute rear light, the indicators in the display tell you that a bulb defect has occurred.

yes, the manual is badly written - tail light only, coz if they wound up the tail light to work as a brake light it would just pop (and we'd have nothing left...)
strange they sort of got it right on the K1300GT - it has two single filament brake lights both dimmed down in normal use