Hi all - I realise that this topic has been covered already elsewhere in the forums but despite all the useful posts that I found, nothing quite matches my issue.

Having been on a 100 mile plus ride last weekend with several other riders/bikes, it was brought to my attention that my headlight was not on - we normally ride with dipped beam on here in the UK.  I did some research on this issue and became convinced that the left-hand switch gear was at fault.  It seems to be a fairly common issue on bikes of a similar age to mine (1984 K100RT). When I came to diagnostics, it seems that if the horn also doesn't work then this almost confirms beyond doubt that the left hand switch gear is the culprit - the horn was NOT working.  On closer inspection however, I found that one or both wires to the horns were broken/disconnected.  Having made good these faults however and with the horn/s now functioning as intended the headlight problems remained.  I do have access to a replacement left hand switch assembly from a farmer friend locally with a K100 spares bike. (He has kindly donated a few spares over the years).  I probably need to mention at this point that the flasher/pass light functions normally). I still need to check/verify all fuses are in good order before I try the replacement.  My question is this - am I on the right track or is there anything else that could be causing the headlight unit not to function as intended by BMW ?

The switch contacts wear out due to the little sparks that are created when you switch the light.  If you install headlight relays then the current through the switch decreases DRAMATICALLY and prolongs switch life.

More here: http://classickbikes.com/ckb.tech/0.ckb.tech.files/hl.relays/hl.relays.htm

duck wrote:The switch contacts wear out due to the little sparks that are created when you switch the light.  If you install headlight relays then the current through the switch decreases DRAMATICALLY and prolongs switch life.

More here: http://classickbikes.com/ckb.tech/0.ckb.tech.files/hl.relays/hl.relays.htm

Thanks for the response duck - I had already found that site/info - seeing as I can try the replacement LH switch gear for no cost I reckon I will go down that road first. However, as pointed out by many owners the original headlight output is pathetic at best then maybe the relay solution is the way forward here.

P S  I have just ordered the Eastern Beaver relay kit - it seems like good value if it can provide better vision of the road ahead.

The power feed for the flash and headlight come from different places. The headlight High/Low beam feed comes from the right switch block through the white/yellow wire in pin 4 of the connector for the right switch and to pin 7 of the connector for the left switch where the power feed for the flash comes from the right switch through the green/blue wire on pin 3 on the connector of the right switch to pin 8 of the connector of the left switch.
Check out the white/yellow and green/blue and see which has power at each switch.
If you dont have a headlight switch on the right switch block also check that the extra connector at the right switch connector is plugged together.  It will be a gray or brown/white wire and will be a separate connector to the 9 pin block.
I had the same fault on the K75 recently (the small connector comes apart easily).

RicK G wrote:The power feed for the flash and headlight come from different places. The headlight High/Low beam feed comes from the right switch block through the white/yellow wire in pin 4 of the connector for the right switch and to pin 7 of the connector for the left switch where the power feed for the flash comes from the right switch through the green/blue wire on pin 3 on the connector of the right switch to pin 8 of the connector of the left switch.
Check out the white/yellow and green/blue and see which has power at each switch.
If you dont have a headlight switch on the right switch block also check that the extra connector at the right switch connector is plugged together.  It will be a gray or brown/white wire and will be a separate connector to the 9 pin block.
I had the same fault on the K75 recently (the small connector comes apart easily).

Thanks Rick G - you lost me at "the power feed for the flash......  Mechanical stuff holds no fears for me but electrical problems are like black magic to me and even though I qualified in 1978 as a Certified Motor Vehicle Technician, I have never been comfortable with wiring/electrics etc.  I can just about handle changing a bulb or a fuse but beyond that I am in the dark - quite literally sometimes

Every failed hi/lo headlight switch I've seen has problems with the low beam contacts where Wht/Yel is supposed to provide power to yellow.

The wire that feeds power to the flash/pass light and headlight come from 2 different places. The headlight High/Low beam power comes from the right switch block through the white/yellow wire in pin 4 of the connector for the right switch and to pin 7 of the connector for the left switch. The power for the flash/pass comes from the right switch through the green/blue wire on pin 3 on the connector of the right switch to pin 8 of the connector of the left switch.
Check out the white/yellow and green/blue and see which has power at each switch.
If you don't have a headlight switch on the right switch block also check that the extra connector at the right switch connector is plugged together.  It will be a gray or brown/white wire and will be a separate connector to the 9 pin block.
I had the same fault on the K75 recently (the small connector comes apart easily).
The connector for the right switch has 10 wires and a 9 pin plug so there is an extra connector for 1 pin which is tucked inside the clear plastic sheath of the 9 pin plug.

I tend to forget sometimes that some just don't understand electricky terms. Sorry for the gibberish so I re did the post.  
As Duck said the switch is the common problem so test for 12v on the white/yellow wire with the ignition on and the switch on if you have a headlight switch on the right side. Cleaning the switch may help but usually the heat generated because of the marginal size lets the plastic melt and the contact sinks back into the switch block and contact becomes erratic and eventually fails completely.

RicK G wrote:the marginal size lets the plastic melt and the contact sinks back into the switch block and contact becomes erratic and eventually fails completely.

That's a better description than mine of how the HL switch actually fails.  Good observation.

might be worth while checking the headlight connector at the globe

I have seen the actual contact section of the globe connecter melted out completely ...on the lowbeam side

the connector is easily acquired and is a standard h4 type connector

im amazed just how small the wiring is to the connector as fitted on the k

a good suggestion is to check out the "eastern beaver"  relay modification and loom options

Thanks to all for the replies - I will investigate further as time permits and of course I will report back the results  

I should also add ....check that the globe is infact working correctly....could it just be as simple as a blown filament ....it does happen !!!

charlie99 wrote:I should also add ....check that the globe is infact working correctly....could it just be as simple as a blown filament ....it does happen !!!

+1. Over time the filament gets increasingly fragile. I was installing an Eastern Beaver relay kit and damaged the lo beam filament while disconnecting the H4 bulb socket. Of course I tested everything else for the failure before I checked the actual bulb.  

Thanks to everyone for their informative posts - what with motorcycle instructing/teaching duties etc I haven't yet had time to investigate further but as soon as I have more news I will report back

Ok - I got some time today to revisit this issue.  I checked/treated with switch cleaner all the fuses and the fuse holder - all fuses were intact and there were no changes after cleaning everything and reinstalling all fuses - still no headlight high/low beams. My next step as time allows will be to check voltages on the yellow/white wire coming from the right switch gear at both ends and to investigate whether the contacts in the left hand switch gear are clean and making contact or have sunken into the switch as suggested above.  I also need to check the bulb filaments, especially before I install the Eastern Beaver relay bits (not arrived yet) so that I can fit a more powerful bulb.  As known to all here, it is almost impossible to access the headlight or park light bulbs without screen removal on the K100RT and even then bruised and skimmed knuckles are the norm. If all the above fails then I will just install the replacement left hand switch gear that I have access to.  Thanks again for all members' comments on my issue

what the ????
easy to access the headlight with instruments in ....but if you have issues getting in there ...try removing one of the pockets ....about 6 screws for a lot more room

right side is usually best

just a thought

charlie99 wrote:what the ????
easy to access the headlight with instruments in ....but if you have issues getting in there ...try removing one of the pockets ....about 6 screws for a lot more room

right side is usually best

just a thought

Ahh yes - I had forgotten that method (bulbs have not been changed in an age).  Thanks for reminding me charlie99

krambo wrote:Ok - I got some time today to revisit this issue.  I checked/treated with switch cleaner all the fuses and the fuse holder - all fuses were intact and there were no changes after cleaning everything and reinstalling all fuses - still no headlight high/low beams. My next step as time allows will be to check voltages on the yellow/white wire coming from the right switch gear at both ends and to investigate whether the contacts in the left hand switch gear are clean and making contact or have sunken into the switch as suggested above.  I also need to check the bulb filaments, especially before I install the Eastern Beaver relay bits (not arrived yet) so that I can fit a more powerful bulb.  As known to all here, it is almost impossible to access the headlight or park light bulbs without screen removal on the K100RT and even then bruised and skimmed knuckles are the norm. If all the above fails then I will just install the replacement left hand switch gear that I have access to.  Thanks again for all members' comments on my issue

Krambo, I have RT with the standard RT fairing and have been able to get the bulbs out without difficulty but it took some effort to work out how. I have a tall screen and found I can get in from the right hand side by standing beside the bike and working by feel and sight. I am left handed but due to a few past breaks my left is not the best. The trick I found was first off the connector plug which is a tight fit and needs to be sort of slowly walked off the bulb, then off with the rubber boot, then the bulb holder can be rotated anti or counter clockwise from the rear and it comes off. The bulb is then free to come out. I decided to practice this in case I found myself in the dark some night. Fitting the bulb worked in reverse and just avoiding touching the glass. There is only room for one hand, it took some trial and error to determine was it better to have the handlebars pointed left or right. If you ever find yourself having to replace a bulb on a dark night and its anyway wet the chances of doing it successfully with high wattage halogen are low. Any wet or dirt and the [expensive] bulb may well pop after a few minutes. The solution is a get you home non halogen bulb, it wont light your way as well but it wont blow so easily and then replace it under better conditions. I am only little though at 5' 8" and not given big hands.

Thank you for your thoughts/insights 92KK - I know that I have replaced the headlight and sidelight bulbs at least once during my ownership of the K100 RT but had completely forgotten what methodology I used.  I will have a go as soon as possible.  As mentioned earlier in this thread, I have ordered the Eastern Beaver relay kit for installation into the system at some point soon.  My thoughts are as follows, because I use this bike for motorcycle instructing most Saturdays I cannot afford for the bike to be in a dismantled state on a Friday night.  Earlier today I found a few hours to return to the job and having got access to a "spare" left hand side switch gear, I thought that I would investigate some of the voltage testing/verifying solutions suggested by others above. Sadly somebody has obviously been there before and the phillips screws have had their heads stripped.  I did manage to undo the left hand side switch screw but the right hand one (the place to test voltages from) has been rounded off.  The only remaining option is to drill the screw out and replace with new/other after I have carried out the voltage tests suggested by others above. Whilst I applaud/admire German technology etc. I cannot comprehend how their minds worked when designing the electrics for the "K" bike.

Watch this space  

you should do all the measurements under the tank ....where the loom makes the connections to the switch assemblies ...
this way you will be testing true values in use ....besides you might just find the issue in those pesky corrosion points down there on the connectors ( but the switches do sound like the most likely culprit ) having said that ...there is something to be said for moving the switches multiple times to help clear the mechanisms of crud that builds up ...even spraying some (shudder ) wd 40 into the switch assemblies does tend to dissolve some of the detritus  

reminder ...slightly longer fuel feed hoses allow one to move the tank back and up without having to strip the fairings off to do so

good luck mate !

Thanks charlie99 - so I can check the relevant voltages from under the tank eh ? I hadn't thought of that ! As already mentioned, I have problems understanding electrical issues. Once the weekend instructing duties are over I will take a look at that area.

Rewired the indicators and both horns today - the wiring is showing its age.  Didn't manage to get the plug off the headlight but am assuming that if the pass/flash switch lights up without issues then the main beam filament at least must be ok ?

Still to take tank off and check connectors under there for voltages to headlight circuits etc. - I will wait until I have some extra hose to extend the fuel lines whilst I am in there - in case I need to go back under there again in future.

Well - the Eastern Beaver relay kit arrived today (I was astonished that I had to pay out another £15.00 customs duty to Royal Mail to release the delivery to me!) Next job is to check/re-check all electrical connections leading to the handlebar switches etc.  I really do not want to try and dismantle the left hand or right hand switches as there are many springy things in there that could escape (for sure they will in my poorly lighted garage) - I will go and pick up the spare/replacement left hand switchgear (and probably the right hand one too whilst I'm there - just in case!) from the donor bike I have access to locally. At least then I avoid having to dismantle the original switches etc. - a prospect that I do not relish !  Will report back with results as soon as I have any more news.  

Thanks to all members that have contributed thus far  

Had the identical issue with my machine.  Rather than checking the bulb first and switch second, like, you, I went through every possible connection, wire, fuse, relay, alternator and battery test first with zero positive outcome.  when all was said and done, the left switch had failed.  Hopefully your issue will be resolved with the switch swap.

Wasted more time a few days ago going through every connection on the bike with DeOxit (something I try to do at least once a year), also squizzed plenty in around the handlebar switches.  Left it all to soak overnight and came back to the bike to check the results. It seems now that I have a dipped headlight beam which mostly stays on (wouldn't trust it on a night ride though) but still no high beam except by using the pass light. Grrr !  I still haven't stripped the left hand switch off the local donor bike but it looks as if I now have no alternative.  Sadly the left-hand switch assembly on mine has had its screw head rounded out so will most likely need to take my Dremel to it and drill the old screw out. (Why did BMW make their screws out of soft cheese?). Thanks to all that have contributed and tried to help me out with this ongoing issue - I am going off the K series bikes sadly - I realise that they are getting old but I now have a dead 1993 K1100LT in one garage (no compression on cylinder 3) and a headlight challenged 1984 K100 in the other garage.  The only bike that is still working as the manufacturer intended is the oldest one of all three (1982 Kawasaki KZ1100 "Spectre").

Krambo,

You are stronger than this. 

Sure a small setback, but I'm sure you can sort it!

Mike

The screws for the combo switches usually have not been turned since they left the factory so some corrosion builds up in the threads given the different metals of the screws and the throttle/clutch perches.  If one pays attention, uses a fair amount of pressure and a good screwdriver then stripped screw heads can easily be avoided.  Blaming BMW is a copout for people who don't know how to wrench properly.

A couple of weeks ago I completely stripped both left and right side handlebar switches. Washed all of the components in plain old laundry soap and water then rinsed in clean water, when dry polished up all of the connections and then taking Duck's advice I drenched all the plastic components in silicon spray and left to dry overnight. Assembled them the next day and all are working smooth as silk.

I did the disassembly inside a clear plastic bag in case some components popped out unexpectedly. I didn't disconnect them from the bike - just put a kitchen stool with a white towel over it as a mini work bench each side.

Have you tried an impact screwdriver for attempting to remove the phillips head screw that holds the assembly onto main block? Even with some damage to the slots in the screw head it might work. Good luck.

duck wrote:The screws for the combo switches usually have not been turned since they left the factory so some corrosion builds up in the threads given the different metals of the screws and the throttle/clutch perches.  If one pays attention, uses a fair amount of pressure and a good screwdriver then stripped screw heads can easily be avoided.  Blaming BMW is a copout for people who don't know how to wrench properly.

duck

I am a fully qualified motor vehicle technician and I find your comments at the very least to be unhelpful and frankly quite insulting.  I am sure that I am not the only person that has found BMW's way of doing things slightly strange and a little bizarre.  I have been removing stripped screws since the days when British bikes led the world.  If you cannot provide genuinely useful information then please refrain from commenting on others' posts  :|

mike d wrote:Krambo,

You are stronger than this. 

Sure a small setback, but I'm sure you can sort it!

Mike

Thanks for the comment mike d - don't worry, I will keep at it until I get a positive result

krambo wrote:

duck wrote:The screws for the combo switches usually have not been turned since they left the factory so some corrosion builds up in the threads given the different metals of the screws and the throttle/clutch perches.  If one pays attention, uses a fair amount of pressure and a good screwdriver then stripped screw heads can easily be avoided.  Blaming BMW is a copout for people who don't know how to wrench properly.

duck

I am a fully qualified motor vehicle technician and I find your comments at the very least to be unhelpful and frankly quite insulting.  I am sure that I am not the only person that has found BMW's way of doing things slightly strange and a little bizarre.  I have been removing stripped screws since the days when British bikes led the world.  If you cannot provide genuinely useful information then please refrain from commenting on others' posts  :|

I was wondering just how long it would take   +1 on that Krambo

krambo wrote:

duck wrote:The screws for the combo switches usually have not been turned since they left the factory so some corrosion builds up in the threads given the different metals of the screws and the throttle/clutch perches.  If one pays attention, uses a fair amount of pressure and a good screwdriver then stripped screw heads can easily be avoided.  Blaming BMW is a copout for people who don't know how to wrench properly.

duck

I am a fully qualified motor vehicle technician and I find your comments at the very least to be unhelpful and frankly quite insulting.  I am sure that I am not the only person that has found BMW's way of doing things slightly strange and a little bizarre.  I have been removing stripped screws since the days when British bikes led the world.  If you cannot provide genuinely useful information then please refrain from commenting on others' posts  :|

I sincerely apologize for causing you Internet butthurt.  I shall no longer respond to any of your posts.

duck wrote:

krambo wrote:

duck wrote:The screws for the combo switches usually have not been turned since they left the factory so some corrosion builds up in the threads given the different metals of the screws and the throttle/clutch perches.  If one pays attention, uses a fair amount of pressure and a good screwdriver then stripped screw heads can easily be avoided.  Blaming BMW is a copout for people who don't know how to wrench properly.

duck

I am a fully qualified motor vehicle technician and I find your comments at the very least to be unhelpful and frankly quite insulting.  I am sure that I am not the only person that has found BMW's way of doing things slightly strange and a little bizarre.  I have been removing stripped screws since the days when British bikes led the world.  If you cannot provide genuinely useful information then please refrain from commenting on others' posts  :|

I sincerely apologize for causing you Internet butthurt.  I shall no longer respond to any of your posts.

Apology accepted unreservedly duck - I guess we were both having a bad day  

Thanks for the info in this thread. One more job ticked off the list to get the old girl back on the road.
No lights, only high beam from left control, so took apart right hand switchgear. Holy crap, more springs, ball bearings and tiny screws than i have seen in a long time.
Connectors all cleaned and rebuilt (after spending an hour searching the garage floor for a missing pin from turn cancel signal) and still no main beam. Read this thread about power coming from left control gear and found all the connectors loose. Stripped down, lubricated and re-soldered. All good now, but did spend 20 mins trying to get parking light working, before checking the bulb!
Another $150 saved!

Dicke wrote:Thanks for the info in this thread. One more job ticked off the list to get the old girl back on the road.
No lights, only high beam from left control, so took apart right hand switchgear. Holy crap, more springs, ball bearings and tiny screws than i have seen in a long time.
Connectors all cleaned and rebuilt (after spending an hour searching the garage floor for a missing pin from turn cancel signal) and still no main beam. Read this thread about power coming from left control gear and found all the connectors loose. Stripped down, lubricated and re-soldered. All good now, but did spend 20 mins trying to get parking light working, before checking the bulb!
Another $150 saved!

Good to hear of a positive result Dicke and also good to hear that my issues and the resulting answers helped a fellow owner to a good outcome

Well, I want to thank everyone who has contributed to this thread as it helped me quickly get over this problem. 

Long story short, I had my headlight, road lights, instruments lights, and rear tail light unexpectedly go out, and fixed it by compressing the connectors under the fuel tank (L & R handlebar switch wire bundle connectors that is).

The long story long is; I treated those connectors with Deoxit two years ago. And, treated the handlebar switches just last winter. So, I knew they were all in good working order. However, I'd just finished wiring heated grips last winter when I noticed the headlight stopped working. Having other things to do, I forgot about it for a few days and unexpectedly the light came back on again. So, I didn't worry about it. 

After riding all summer I was leaving work last week after dark, and didn't notice the headlight had gone out until I was a block or so down the road. I'm 40 minutes from home, and after checking all the fuses I decided I could hold down the high beam Flash switch and travel most of the way home by the freeway. No tail light mind you, but do have rear LED lights on my helmet and a passive reflector on the tail light lens. Still, I didn't know how I'd make it through town once I got off the freeway, but figured I'd go as far as possible then call for a ride.   :pale: 

On the way it started to rain, and I was getting worried. Holding the Flash switch down for 10 minutes straight caused my thumb to ache, and at some point I had to let up. Praise the Lord (if you're that kind of person)--the lights miraculously came on, and I drove the rest of the way home without further incident! Next day, lights wouldn't come on at all.

 
P.S. Next winter I'm installing a headlight relay, and will configure my road lights so they are completely independent of the handlebar switches if this should happen again.

I picked up a really inexpensive ceramic automotive relay set off fleabay and run a 12 gauge wire back to the starter relay and one to ground.  Mounted relays off the back of the glove box and tied off the extra plug vbecause I din't have my side cutters handy to trim it off