Morning all,

             A few weeks ago i noticed one evening that the red warning light was very slightly coming on and off while i was riding.  This only happens around the 4k rev range.

It is so slight that it's not easy to see it coming on but it is.  Today while riding to work it came on and off again but brighter this time..and then it lit bright and full.  I wondered if i had a rear bulb failure so i pressed the rear brake and the light went out.

But a short time later it started flickering again.

So do i have a short, a bad earth, a charging problem or a bad battery.  everything on the bike is standard and not been touched for years so i don't know how old anything.

The alternator is charging at 14v and all else is fine with the bike running.

Any ideas please as i still very new to this bike.

Mike

The alternator is in the tacho part of the cluster and will have a small battery symbol next to it. Is this the light as it should be the only one to come on if the alternator stops charging. There are several other red warning lights but none that would be or have any affect on the charging system.

more than likely the brushes in the regulator of the alternator

these are known to go intermittent ...and certainly at different vibration - load

we have all noticed some glow  at night from the "charge" indicator

could it be that with low use that the comutator ...brush set is bouncing around a bit and still cleaning up its path ...

but otherwise the regulators aren't horribly expensive ...and you might just save your battery by changing it early rather than after  a fail event ?

RicK G wrote:The alternator is in the tacho part of the cluster and will have a small battery symbol next to it. Is this the light as it should be the only one to come on if the alternator stops charging. There are several other red warning lights but none that would be or have any affect on the charging system.

The red light that i am talking about is the big one in the centre of the instruments.  Between the main beam and neutural lights.

It's the one that comes on at first power up and then goes off when i operate both brakes.

Mike

That is to do with the bulb monitoring and the brake light circuit when you first start it and ride away
If it is flickering check the connections to the brake and tail lights if one of them is intermittently losing the contact that will make it flicker and replacew the bulbs as we have found several times thet the bulb looks OK but is not at its best.
If you have ABS it will flash in unison with the ABS light in the speedo if there is an ABS fault.

RicK G wrote:That is to do with the bulb monitoring and the brake light circuit when you first start it and ride away
If it is flickering check the connections to the brake and tail lights if one of them is intermittently losing the contact that will make it flicker and replacew the bulbs as we have found several times thet the bulb looks OK but is not at its best.
If you have ABS it will flash in unison with the ABS light in the speedo if there is an ABS fault.

I thought it might be that so i'll change the rear brake buld.  I've got an 87 K100LT pre ABS which makes it eaiser.

Cheers for the advice.

Mike

And the tail light bulb as well Mike
It's a good idea to put the year and model of your bike in the signature line t6hat way we all know what we are refering to without having to ask or tell each time.
Then you got the guys like Duck that have so many that they need a page just for that, I am only jealous.

It is so slight that it's not easy to see it coming on but it is.  Today while riding to work it came on and off again but brighter this time..and then it lit bright and full.  I wondered if i had a rear bulb failure so i pressed the rear brake and the light went out.

The charge light should get brighter when you press the brake like this. Either way it doesn't matter because it does tend to light a little at night with lights on and pressing the brake.

The centre one, already mentioned, is the bulb monitoring. Check and recheck the brake light bulb and circuit, I had a similar experience on the LT and found corrosion on the bulb. Cleaned it up and then swapped the 5/21W for a 10/21W bulb and all cured. don't use the 5w, its just not safe, not bright enough on a bad night. You can take out the bulb holder and clean up the connections.

yep to all the above

the bmu is a strange beast but worth every cent of it .

Could be as simple as an iffy contact on the brake light switch. If it's the rear brake then remember where the switch sits behind the footrest plate, perfectly placed to get covered in crap.

Mine won't do that as I have thrown away the BMU. That is the only way to fit LEDs in the back.

The occurrence at 4,000rpm is a clue because that's peak vibration on the K.

I have some LED lights on the way and interesting to note that the BMU must come out, is there a way to keep it. While the LED will definitely last longer it does also pick up a bad connection which is more likely due to the age of the K.

You can leave the BMU in but then you must use resistors which will defeat part of the reason for fitting LEDs in the first place. Much easier to remove the BMU as the LEDs will last the life of the bike, in theory.

I don't understand the electrickery but I fitted some LEDs that go on with the the brake light (kindly supplied with instructions by '88'  ) and this does not have resisitors (I don't think) and I still have the BMU?

Do you mean you need to remove the BMU when you replace the exisiting bulbs with LEDs?

Cheers
Dave