Hi all -

I think I have a faulty load shed relay.  Leaving work this afternoon I found both left/right signals inop, then towards the end of my ride they both seemed to come back to normal.

Shut the bike down once home, then went to check them (ignition switch to Run) and now no signals or headlight.  I've had the relay go out before and had these similar symptoms.

I did swap the horn and load shed relays in the Relay box and still no headlight, signals (or horn).  Checked fuse continuity and all check good.  I will go back and clean up the fuse contacts as a next step. 

Bike does start, no issues with starter relay.  

Looking for a simple diagram that shows which pins to run +/- power and which to measure voltage (?) with my multi-tester.

Full disclosure, I have changed out to LED signals (and am using resistors, didn't go into the flasher relay) and they've worked fine until today.  I don't think its my LED mod.


Thanks,
Tony Marts

sounds like the old dirty starter motor brushes ,,

get the kit from your friendly bmw guy , both the mounting plate and the additional brush

starts ok says that there could be some resistance ( although not affecting start ) but the starter could rotate to a similar position where the commutator is dirty

at high currents no issue ...but allowing the load shed to operate  could be an issue ...

don't forget to replace your fuses ...the flasher unit has 2 sources of power

and fuses are often an looks ok issue but the contacts corrode etc

good luck

+1 on the starter motor brushes. This is a common problem that effects all K's right through to the later K1200's as they get old. All sorts of gremlins come out to play when the brushes/commutator are dirty as the starter is a path to earth for some electrical items.

And another one here agreeing with that.

There's an easy way to determine if the starter brushes are the reason for your load shed relay not energizing.  Take a jumper and connect the starter terminal to ground.  If the headlights turn on then your starter is your problem.  DO NOT PUSH THE STARTER BUTTON WHILE DOING THIS.  BAD THINGS WILL HAPPEN.

Thank you all for the input.  I'll do the fuses and also try the starter to ground test, and the brush re-build.  

I've been through the ignition switch and starter clean procedures several years ago when I ran into no-start issues.

kioolt wrote:There's an easy way to determine if the starter brushes are the reason for your load shed relay not energizing.  Take a jumper and connect the starter terminal to ground.  If the headlights turn on then your starter is your problem.  DO NOT PUSH THE STARTER BUTTON WHILE DOING THIS.  BAD THINGS WILL HAPPEN.

Unfortunately this quick check didn't reveal anything.  I've pulled the starter and disassembled it in prep for the clean and new brushes.

hmm perhaps the relay is cactus ..? 

you did turn the ignition on and the run switch in the right position ? whilst conducting the previous earth the start motor test ?

else a under tank connector issue from the kill switch back to the loom ?

'might have to trace the power through the maze of connections ...im sorry 

the interactive electrical diagram could perhaps help with this .(on the portal page )

tonybob wrote:

kioolt wrote:There's an easy way to determine if the starter brushes are the reason for your load shed relay not energizing.  Take a jumper and connect the starter terminal to ground.  If the headlights turn on then your starter is your problem.  DO NOT PUSH THE STARTER BUTTON WHILE DOING THIS.  BAD THINGS WILL HAPPEN.

Unfortunately this quick check didn't reveal anything.  I've pulled the starter and disassembled it in prep for the clean and new brushes.

If you grounded the starter terminal and the load shed relay did not turn on to make your headlight work then it showed you that the starter is not the problem.  That was the purpose of the test.

charlie99 wrote:hmm perhaps the relay is cactus ..? 

you did turn the ignition on and the run switch in the right position ? whilst conducting the previous earth the start motor test ?

else a under tank connector issue from the kill switch back to the loom ?

'might have to trace the power through the maze of connections ...im sorry 

the interactive electrical diagram could perhaps help with this .(on the portal page )

Yes to both.  I thought at first the load shed relay went bad, so I swapped it with the horn relay.  No luck there either, so that's why I originally thought it might not be a bad relay - both horn an load shed going bad at the same time seems remote.  

I've had to wait on the brushes for a few days and they should be in at my dealer today.  Probably won't get to the re-build until this Friday or the weekend.  

Next step after the starter re-build would be to get a new relay, and if there's still an issue then it's time to pull the tank and start tracing.  I do have a color wiring diagram to use, so at least I'm ready if it comes to that.

Most of the time the brushes are fine. What happens is carbon builds up on the commutator, and once cleaned everything returns to normal. Probably should be part of your regular maintenance I had to mine at 150,000 K's dirty commutator only, brushes still fine. It is a good idea to smear some Copper Kote where the starter inserts into the housing. A mates starter had to be removed with a slide hammer due to corrosion between the two.
Regards Martin.

Got the new starter brushes installed plus cleaned out the inside of the body and end caps.  Starter works great now.  Unfortunately, did not do the trick.

I'll be picking up a new relay and trying that next.  Next step then is pulling the tank and tracing through the wiring.

tonybob wrote:Got the new starter brushes installed plus cleaned out the inside of the body and end caps.  Starter works great now.  Unfortunately, did not do the trick.

I'll be picking up a new relay and trying that next.  Next step then is pulling the tank and tracing through the wiring.

Well, turned out to be a bad relay after all.  Finally go a new one and lights working again.  

Strange thing, the first thing I tried was to swap out the load shed and horn relays.  Neither worked at the time.  Today I double checked both original relays and one is inop.  The second does work for the horn. 

I'll go back and re-check the wiring schematic, but I was thinking the horn relay power is fed from the load shed relay.

In any event, this one is probably traced to human error (as HAL would say).

I should have added that the bike is an 85 K100RS, with 57k miles on the clock.  

Next major repair is going to have to be the rear main seal.  The oil drop on my garage floor are starting build a larger spot.

Thanks all for the input for troubleshooting.  Nice to know there are so many dedicated riders for these old K-bikes.