85 K100 Flickering lights

I wrote about this problem a few months ago. It seemed to have gone away, but it is back with a vengance.

I was out on a long ride yesterday, trying to eke out a few more miles for the contest. Late in the afternoon, the headlight and instrument cluster started flickering. I was riding a curvy road pretty aggressivley. The guy on the Harley cruiser was not happy when I blew by him

This first happened last May. It only did it one evening, then once again a few weeks later. It seemed that shutting the bike down and restarting it 'fixed' the problem. Then it happened again in early September, with more persistence. I took it to the shop (local guy who works on Beemers). The guys witnessed it. At that time, the left front turn signal was also not working. They had the bike stripped down, troubleshooting it. That included having the headlamp assembly completely removed. The turn signal problem turned out to be a couple broken wires in the harness. They fixed that and the lights all worked fine for 2500 miles and a little over a month.

Here are the facts:

I ride the bike to work every day and take some rides on the weekends. So it isn't like she sits all the time. The lights have been working fine since the rewiring job.

I noticed that as long as I had the bike over 3000 RPM, the lights didn't flicker other than a very occasional blip. Otherwise they are fine.

When slow down under 3000 RPM, they begin to flicker.

It does it in both High and Low beam.

The instrument cluster backlights flicker when the headlamp flickers.

The Alternator indicator, which faintly glows all the time and has since I got the bike, doesn't glow brighter or dimmer during the flickering.

The Choke lamp doesn't flicker at all.

When the flickering is happening, the turn signals act strangely. They blink irreguraly and sometimes both front ones come on.

I don't know if the tail light is affected.

When I stop the lights flicker, go completely out, then suddenly come back on.

When riding through town, if I gear down to keep the RPM's above 3000, the lights work normally.

When I tip the bike over, about as far as putting it on the sidestand to either the left or right, the flickering stops. If I hold the bike upright, it flickers.

If I shut off the bike and leave it rest for a few minutes at a gas stop, the lights work normally for a few minutes, then start flickering again.

Even when it is acting up, the bike starts and runs fine.

She has about 140,000 miles and 22 years on her.

The bike was a K100RS with a Pichler fairing. After an accident, I had her converted to a K100, taking off the fairing and having a round headlight assembly installed. I say this because I want to state that Things Are Not Original Up Front and Up Front Is Where I have The Problem!

I don't do my own wrenching, but I know how hard intermittent problems can be to diagnose.

What could be causing this? Wiring? Could the H3 bulb be going out? (If so, why does the cluster backlights flicker also?) I know that the starter brushes can cause headlamp problems, but what about the instrument cluster? Could the alternator cause this? Would the instrument cluster or its connector cause this?

Any suggestions on what I should do, or have my mechanic check?

We deal with issues like this quite often with our products over 10-15 years old. We make gauges for can inspection systems (Anheuser-Busch, Coke, Coors...).

Not seeing the bike personally, it's hard to ascertain the reason for the issue, but the damaged connection to the indicator tell me that there could be more damage unseen.

I think you have a contact problem. They may have checked all of the connections, but did they disconnect all of them and then reconnect them again? If not, then one of the connectors could be "mostly" connected (or partly disconnected). This could be the result of whatever damaged the signal connections, or could simply be some corrosion on the contacts.

If the connect ion is weak, then higher revs you may have more current which could flow even though the connection is weak.

If the bike is tilted, then there could be some more weight (either from the weight of the connector, or possibly from something that you are holding onto - tilting the handlebars all to way to one side?).

We see this when there is a "cold solder joint". This issue is very hard to find, because these joints look nearly identical to good solder connections. About the only way to find it is to heat up all related connections, and hope for the best.

I would borrow someone's maintenance manual and trace all related connectors. Disconnect them, clean the contacts with some isopropyl alcohol and then put them back together again.

This may not solve the problem, but at least you should be able to rule out most the connections.

Good luck...

One more thing... After the accident, did you do any work with the fuse box? This could have been compromised in the crash, and could be shorting out...

Electrical issues really stink... Sorry you are dealing with it.

godzilla said:

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What could be causing this? Wiring? Could the H3 bulb be going out? (If so, why does the cluster backlights flicker also?) I know that the starter brushes can cause headlamp problems, but what about the instrument cluster? Could the alternator cause this? Would the instrument cluster or its connector cause this?

Any suggestions on what I should do, or have my mechanic check?

Click to expand...

See: http://www.eilenberger.net/K75S/IgnitionSwitch/index.html - not an uncommon problem actually.

deilenberger said:

See: http://www.eilenberger.net/K75S/IgnitionSwitch/index.html - not an uncommon problem actually.

Click to expand...

One addition to my suggestion - try wiggling the key in the on position (engine not running) - if the instrument lights flicker - it's the switch needing cleaning.

UPDATE!!!!

This morning, the brake warning light stayed lit, not clearing after tapping the brake levers. I checked my tail lamp and it was out.

I rode the bike anyway, more for troubleshooting purposes because this happened recently and went away after a mile or two. IT didn't this morning. I gather that when the brake warning light stays lit, that indicates a tail light problem?

Whe I got to work, I pulled out the tail lamp and it is dead; the filamant is broken. I will stop on the way home and replace the bulb.

I also noticed that the tail light DOES flicker in synch with the headlamp and cluster lights and so does the Brake Warning lamp. (My license plate holder has lights that work with the tail lamp and the brake lamp.) The brake light works fine (separate bulb on the K100).

The question is (guess I will answer this myself later), could a failing tail light cause the both the high and low beams lamps and the indicator lamp to flicker? Even with the tail lamp completely out, the symptoms remain, just as noted above. I revved the engine in the parking lot and duplicated the 3000 RPM thingy.

I will take a look at the ignition switch information as well. I have a Clymers; I plan to look through that.


Which one of you guys will come to Indiana to help me fix this thing?

And rob you of the satisfaction that will come once you've fixed it on your own?


I looked at Deilenberger's link, and this sounds like a very likely culprit to me. It falls right in line with a "contact issue", and that would certainly kill all of the lights.

Have you noticed anything with the engine performance? Does there seem to be a loss of power when the lights are flickering? An ignition switch issue should cut power to everything; not just the lights. The motion of the engine should keep it running if it's just a flicker, but there may be some hesitation... Could be hard to tell at lower RPM's (when the flicker is most evident).

Again, good luck!

grossjohann said:

And rob you of the satisfaction that will come once you've fixed it on your own?


I looked at Deilenberger's link, and this sounds like a very likely culprit to me. It falls right in line with a "contact issue", and that would certainly kill all of the lights.

Have you noticed anything with the engine performance? Does there seem to be a loss of power when the lights are flickering? An ignition switch issue should cut power to everything; not just the lights. The motion of the engine should keep it running if it's just a flicker, but there may be some hesitation... Could be hard to tell at lower RPM's (when the flicker is most evident).

Again, good luck!

Click to expand...

Nope, the engine runs fine when the lights are flickering. So surging or missing. Plenty of grunt, no hesitation. I was sitting at the gate this morning while the gaurd checked my id. The lights were completley OFF and the bike was idling smoothly. I was waiting for them to tell me to go back home since the headlight was furiously flickering as I approached the gaurd shack. As I stopped, the lights went out. They didn't say a thing and off I went, giggling. So, no, the engine is NOT affected.

Could that be a sign that the alternator is failing, even though that indicator doesn't light up? I know when My Truck's alternator failed on me, the engine ran fine, but the lights dimmed as the battery drained down. Any thoughts on that? I don't think the battery is draining on the bike since it starts fine every time...

grossjohann said:

One more thing... After the accident, did you do any work with the fuse box? This could have been compromised in the crash, and could be shorting out...

Electrical issues really stink... Sorry you are dealing with it.

Click to expand...

No, the fuse box was OK. The crash was way back in 2001. I have put about 70K miles on since that little incident.

WHen they were working on the turn signal problem, they had the headlamp bucket removed and were goofing with all the wires inside the bucket, tracing out the missing ground and power wire going to the turn signals. They also had the relay box open, swapping out the turn signal flasher relay, trying to troubleshoot the busted wires in the harness. To fix the busted wires, he cut all the wires and resoldered them to make the harness a little longer. He shrink wrapped all the wires that he spliced. The break in the harness was right where the harness rides along the forks. The harness wore through and broke a couple wires.

Would a problem in the tail light affect the headlamp and cluster? Obviously there is a feed from the brake and tail lamps up to the cluster for the Brake Warning indicator and a feed back for the turn signals. How are the headlamp and tail lamp connected in the curcuit? Could the instrument cluster itself be the problem since it is common to everything?

Like I said replacing the defective tail lamp might solve the whole issue, but I am curious to know why a broken tail lamp would have such an effect on the entire electrical system except for th engine itself.

I'll grill the steaks and provide beer AFTER THE BIKE IS FIXED for anyone who wants to come fix this thing!

godzilla said:

No, the fuse box was OK. The crash was way back in 2001. I have put about 70K miles on since that little incident.

WHen they were working on the turn signal problem, they had the headlamp bucket removed and were goofing with all the wires inside the bucket, tracing out the missing ground and power wire going to the turn signals. They also had the relay box open, swapping out the turn signal flasher relay, trying to troubleshoot the busted wires in the harness. To fix the busted wires, he cut all the wires and resoldered them to make the harness a little longer. He shrink wrapped all the wires that he spliced. The break in the harness was right where the harness rides along the forks. The harness wore through and broke a couple wires.

Would a problem in the tail light affect the headlamp and cluster? Obviously there is a feed from the brake and tail lamps up to the cluster for the Brake Warning indicator and a feed back for the turn signals. How are the headlamp and tail lamp connected in the curcuit? Could the instrument cluster itself be the problem since it is common to everything?

Like I said replacing the defective tail lamp might solve the whole issue, but I am curious to know why a broken tail lamp would have such an effect on the entire electrical system except for th engine itself.

I'll grill the steaks and provide beer AFTER THE BIKE IS FIXED for anyone who wants to come fix this thing!

Click to expand...

Well, honestly, I don't have answers to many of your questions. There is feedback to the instrument cluster from the brake lamp (otherwise there would be no indication that the lamp had burnt out), but I doubt that it would cause the flickering; unless all the lights were in series - which could never be...

If the lights were totally out at idle, then I would not suspect the ignition since the engine would have probably stalled out, or stopped.

The alternator sounds like a good angle because it may not be putting out enough charge to run the lights and charge the battery while the engine is at low RPM's, but like you said, battery trouble usually comes with alternator trouble.

Have you looked around to price out the instrument cluster? If you could get one from http://www.beemerboneyard.com/ or similar parts dealer, then you may want to replace it and see if the issue persists.

I may need to head out to visit a customer in the South Bend area in a couple of weeks... He's having electrical trouble with one of our products. Oddly, their issue seems to be a "phantom" electrical connection, too.

Maybe you don't want my help after-all...

grossjohann said:

Well, honestly, I don't have answers to many of your questions. There is feedback to the instrument cluster from the brake lamp (otherwise there would be no indication that the lamp had burnt out), but I doubt that it would cause the flickering; unless all the lights were in series - which could never be...

If the lights were totally out at idle, then I would not suspect the ignition since the engine would have probably stalled out, or stopped.

The alternator sounds like a good angle because it may not be putting out enough charge to run the lights and charge the battery while the engine is at low RPM's, but like you said, battery trouble usually comes with alternator trouble.

Have you looked around to price out the instrument cluster? If you could get one from http://www.beemerboneyard.com/ or similar parts dealer, then you may want to replace it and see if the issue persists.



I may need to head out to visit a customer in the South Bend area in a couple of weeks... He's having electrical trouble with one of our products. Oddly, their issue seems to be a "phantom" electrical connection, too.

Maybe you don't want my help after-all...

Click to expand...

Actually I am on a replacement cluster already. The original got wet and went totally bonkers, then completely died last year, so I got one from a guy in NC. Most everything work on this one, other than the gear indicator. and the Tach bounces. I wouldn't rule this out as being the cause though.

I had to go to a meeting this afternoon and thought I would look at the repair job done to the wiring. It seems fine, but I noticed a second harness running parallel to the fixed one. The tape wrapping is worn off, exposing the wires. I fiddle with the wires, looking for a broken or stripped wire. All looks OK. The lights worked fine, but I only had 1 mile to the meeting and back, and that isn't enough time for the problem to occur. Well, the tail lamp is still out and the brake warning light is still lit, but I know for sure that the tail lamp filament is gone in the bulb...

Hmm South Bend? Well that is a bit of a ride... I live on southwest Indiana, directly south of South Bend (in Indiana we like to say South Bend is in the north and North Vernon is in the south!). But it is a good distance. Seriously, I would pay to get this problem fixed by a knowledgeable person, along with a Steak!

Replacing the tail didn't help. Oh, the tail light works and the brake warning indicator is off, but the lights still flicker.

I think I am going to make an appointment with Wilbur to drop her off for rehabilitation. Mrs. Godzilla doesn't want me to ride with no lights in the rain this week.

My Riding To Work Streak will officially end as of 10/16/07. I had ridden every day since May, when I was working 16-hours days and not getting home until after midnight. That was the first time the flickering lights happened...

I did notice that when I stopped at the auto parts store to get the new bulb (I bought two!), that if I lean the bike to the left (side stand) the flickering quit and the lights worked. Leaning it as far as I could to the right didn't help.

When I started the bike up, they worked fine for about 5 minutes before the flickering came back. That is normally what happens. When I got home and stopped in front of my garage, the lights were off. I tried jiggling the key, but that didn't do anything. SHutting it off and restarting the engine brought the lights back on with no flickering at all, no matter what I did.

Could the headlight relay cause the entire lighting system to short out or open up, causing the problem? I am not totally sure, but don't ALL the light shut off when you start up a K until the engine fires? Would that indicate a possible relay or relay grounding problem? What is the common point for the tail lights, headlamps and the instrument cluster lights? Before the relay or after the relay in the circuit? Would a relay be affected by the lean angle of the bike like that? I wouldn't assume that the ignition switch or the starter brushes would be affected that way. But what the hell do I know?

Sorry about the ride to work streak, but I'm glad you're taking him in... I would explain what you posted here, and show them the leaning "fix".

Let us know how you make out.

OK, I dig out my Clymers and am looking at the wiring diagram in the book. I don't quite understand it. The headlamp feed into a connector called the "Connection for Special Equipment" and I can't figger out what that is for or where it goes. The tail lamp goes into a "Bulb Monitoring Unit". I see something like that noted in the instrument cluster. But nowhere do I see where the headlamp has anything to do with the tail lamp and cluster?

What am I missing?

deilenberger said:

See: http://www.eilenberger.net/K75S/IgnitionSwitch/index.html - not an uncommon problem actually.

Click to expand...

Question! Does the starter circuit and the light circuit share the same switch posts on the ignition switch? Looking at the pictures on the link, they don't appear to do that. I don't have my Clymer's with me at work, so I can't reference it at the moment...

I am trying to decide in me head space why the lights are affected and apparently not the starter. I am also trying to figger out how the tail light can be affected, so where does the front end lamps meet up with the tail lamp. Since all the flickering lights come on when the key is turned, they have to meet up somewhere and this would be a logical place for failure.

And if there is only one switch post for the lights and starter curcuit (I would guess that goes to the starter button), do both circuits share common wires? Or does the light curcuit 'meet up' with the starter circuit at the switch itself?

Would a place to start be troubleshoot the wire from the ignition switch back to wherever in the hell it goes? And just where in the hell DOES it go? Back to the Load Sharing Relay that turns OFF all the lights when the starter button i smashed? So would that be the next culprit?

I have been told that the headlight is grounded through the starter brushes, causing problems. But do the cluster lamps and the tail light ALSO ground through the starter and the Load Sharing Relay?

Could a failing relay exhibit these weird symptoms? Would it catch under higher RPM's and work when it is leaned over so far?

The ign switch has separate contacts for the lights and ign. So it could be the switch. Also could be the starter brushes. Since you have no starter issues, I would try the switch first.

cjack said:

The ign switch has separate contacts for the lights and ign. So it could be the switch. Also could be the starter brushes. Since you have no starter issues, I would try the switch first.

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Thanks, Chuck! I am going to take a print out of the link in the previous message and let the mechanics try that first to see if it fixes it.

godzilla said:

Thanks, Chuck! I am going to take a print out of the link in the previous message and let the mechanics try that first to see if it fixes it.

Click to expand...

Somewhere in a thread a fellow just learned that you can remove the red paint from a dot under the ign switch assembly back a slotted screw out and the switch itself will come off the bottom easily without removing the whole assembly. I remember that and it is good info if you are doing it yourself, etc.

cjack said:

The ign switch has separate contacts for the lights and ign. So it could be the switch. Also could be the starter brushes. Since you have no starter issues, I would try the switch first.

Click to expand...

Thanks, Chuck. It looks like I was loosing the trail.

godzilla said:

Question! Does the starter circuit and the light circuit share the same switch posts on the ignition switch?

Click to expand...

All switched power goes thru the ignition switch. Basically. battery voltage is wired to the center connector (red) of the ignition switch and this is then switched to various outputs as the key is turned. This would include the headlight. The starter relay is switched but the starter itself is not.

FWIW, I spent a long time trouble shooting an electrical problem with my K75. Everything I tried *seemed* to help for awhile but the problem always returned. I replaced the battery, alternator, starter, cleaned all sorts of connectors, cleaner the injectors, even disconnected my Hyperlites. Turned out that the power input connector in the ignition switch was making intermittent contact. I think that all my troubleshooting included a fair number of switching on/off and starting which was probably wiping the contact slightly cleaner. Removing and cleaning the ignition switch solved my problem completely.