Im working on a friends K1, first had ABS probs but they are all sorted now,
everything now works as it should but the warning light is now coming on when i run it with lights,
On startup it comes on as normal and i press the front and rear brake and it goes out until i turn the lights on, and then it stays on solid unless i turn the lights off again
Is this normal or is there something i can check.

I have a haynes manual but it does not go into any detail about the warning light!!

Your tail light is probably not working and if it is then change the bulb. No guarantee but that is the usual problem.

cheers Rick,
the brake & tail lights both work and i have replaced both with new just to check

The warning light (at least on my K100RS '87) only warns of failure of the rear brake and rear light.

So what you are seeing is "normal" - in that it thinks that the tail light is blown.

You are correct in that, if it goes out when you press both brake levers - the brake light is working. If it turns on when you turn on the lights, then the rear tail light isn't working - or in your case it "thinks" it isn't working. If you are sure that the rear light is working, then it is a problem with the warning light mechanism - but to do with it's reading of the rear light. Hope this makes sense.

You will have to go through the wiring diagram to check the various componants.

Were there any changes to the tail light? Different wattage bulb? LED bulb etc?

The warning light does not warn about the front light.

we have seen a fair bit of corrosion around the taillight and connections
you will notice a molex type connector just before it goes to the actual tail lamp assembly

worth cleaning up those , and also the spade connections to the actual assembly on the tail light ,,,deoxit is brilliant stuff for most of these issues

Hmmmm, will take a look through the connections this morn and see if i can find anything causing the prob, could it be the relay?
searched the forum and a lot of probs seem to relate to that so would it be worth checking?

Ruddiger wrote:Hmmmm, will take a look through the connections this morn and see if i can find anything causing the prob, could it be the relay?
searched the forum and a lot of probs seem to relate to that so would it be worth checking?

I don't think there is a relay in the bulb checking circuit. I'd check the connections as Charlie99 suggested.

If you are referring to the starter motor relay, then that causes problems when the battery is low. The low power causes the contacts to not close properly when starting. The current arcs between the relay contacts, which welds the contacts together (don't ask how I know). A different, though common problem, and had no bearing on the issue you are having with the warning light.

At the moment, my money would be on a poor connection back to the check light from the tail light bulb. So the bulb lights as it has power and ground, but the power isn't travelling back to let the warning circuit know that the bulb circuit is closed, i.e. the bulb is ok and lighting.

sorry, i meant the mwu(bulb monitoring unit) not a relay, saw a few posts about them causing trouble,
checked the wiring and its good, the wires run straight from the terminals on the bulb holder straight to the electrics box,
also tried swapping the bulbs and the holders from the brake light around to see if that would make a difference but no joy!

thought i had it at one point when it went out but it had blown the fuse.......

problem solved

borrowed a bmu from another k100 and the warning light didnt work at all so put the original one back in but gave it a couple of taps incase it had got stuck and it worked!

cheers for all the help guys

sounds like you have the old bad solder issue in that bmu

some one else posted similar issues in here just a few days ago