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1Back to top Go down    Low beam headlight not working! on Sun Apr 24, 2016 2:13 am


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Gold member
Hi all

I have a 1984 Bmw k100 which is running well except for the headlight.
The bike is in reasonable condition. There is no rust and the wiring is in good condition.
I did a visual check of the fuses.
The high beam works when I press down on the yellow switch on the left hand side. I have to keep the switch pressed down for the high beam to work. If I push the yellow rocker switch upwards, the high beam does not work.
The park light also does not work.
The rear park light is fine.
I haven't checked the relays? Or cleaned the left hand side switch.
All replies appreciated.




2Back to top Go down    Re: Low beam headlight not working! on Sun Apr 24, 2016 2:46 am


sounds like the wiring from the right hand switch isn't making it to the lefthand switch

by pressing the button down on the left switch are activating a secondary power feed just used for the flash process

possibly there is a switch or wiring issue under the tank ? but likely at the right hand switch ?

so would be good practice to go under the tank and measure - probe those connectors before continuing

many have had similar issues

but I don't know weather you have the lights normally on as some us models are wired for permanent low beam

hope that makes some sense

I recently refurbished my high low switch assembly ...which needed it

have a look here might help


cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O

3Back to top Go down    Re: Low beam headlight not working! on Mon Apr 25, 2016 6:18 am


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hi Gabriel , ditto here mate .
mine is doing exactly the same.
I am sure that mine is in the contact point of the RH switch, as I had it attended to by the Auto leco a couple of years back . He added some solder inter the cluster to help get through rego.
During Pauls recent visit it was showing signs of needing further attention .possibly due to the softness of the solder, it has worn down again .
Beware not to solder , with extreme heat , as recommended by the Krew.
I kept myself to daytime riding , finishing at dusk each day .Always on the alert for those unable to see me .
just a thought before puling the bike apart ,
A quick diagnostic is toremove the RH switch cluster and add some foil or conductive material between the contact points ,
and see if it works , if so there lay the problem. Ed.

1987 K100RT Ex- police
1989 K100LT Ol' Blue and "Kart" the Kamper trailer. now KAPUT .
1993 K1100RS 0194321 Colour #690 Silk Blue aka" Smurfette"

4Back to top Go down    RH elec switch gear on Mon Apr 25, 2016 6:37 pm

klompy the grey brick

Having done this myself I strongly recomend pulling the switch apart inside a plastic bag...this is a method recommended by a wise K100 dismantler so that you do not watch the tiny springs dissappear into the darkness.

Get some relays fitted ASAP as they take the heat off the switches literally and were sadly left out by BMW boffins.

Good luck the path you travel has been travelled before welcome to the club.

"Grace" 1984 K100RS Silver VIN 0019026 Mitt eine Staintune Zorst.
"Olivia" 1997 K1100LT Dark Grey VIN WB1052600W0237453.

Chassis number0019026
Vehicle code0503
ModelK 100 RS 83 (0502 ( 0503 )
Body typeK 100 RS 83 (0502
Catalog modelECE
Production date1984 / 07


5Back to top Go down    Re: Low beam headlight not working! on Mon Apr 25, 2016 7:50 pm


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Life time member
+1 on the above - headlight switch on right side the most likely culprit. Putting in relays will take the pressure off the switch, with the bonus of allowing a more powerful headlight bulb to be fitted without refrying the switch.

Front parking light is most likely just the bulb if the rear is working.


1985 K100RT VIN 0028991 My original Very Happy (Historic rego)
1985 K100RT VIN 0029036 BOB the Blue Old Bike (Historic rego)
1990 K100LT VIN 0190452 Work in progress
1984 K100RT VIN 0023022 Work needing lots of progress

1986 K100RT VIN 0090542 Work needing lots and lots of progress
1993 K1100LT VIN 0183046 Work in progress
1993 K75S VIN 0213045 Newest toy, slightly non-original

6Back to top Go down    Re: Low beam headlight not working! on Mon Apr 25, 2016 10:35 pm


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Life time member
It could be the right hand switch but that switch does not get used much. Mine looks to be in very good condition inside. However the left hand switch gets a hiding especially if there are no relays installed. Gaz did a very nice write up about refurbing the left hand highbeam switch contacts. Worth investigating imo.
Reparing left switch block

Also DaleRT did a similar repair Re: Headlight Trouble

Regarding the parking light. If the tail light is working then the front parker is getting power too and the fuse#2 is ok. Must be somewhere in the wiring forward of the fuse, the bulb, bulb fitting or on the earth side.


1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90

7Back to top Go down    Re: Low beam headlight not working! on Mon Apr 25, 2016 11:00 pm

RicK G

Hey Gabreil first of all is there a yellow switch on the right side switch block, many bikes of the early 80s to mid 90s had hard wired lights in that the headlight was on all the time, There is a white/yellow wire from the right switch to the left switch that supplies power for the headlights and the flash of the high beam is done from a different power source so that it can be flashed without the headlight being on.
If there is no right switch then the power comes into the left switch on that w/y wire but it is powered all the time via some grey jumper wires on the plug under the tank.

"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats." from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now

8Back to top Go down    Re: Low beam headlight not working! on Thu May 19, 2016 1:45 pm


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Gold member

Thanking you for your suggestions and advice.
I still don't have a functioning headlight. Sad
Latest updates...I opened the left hand switch and the contacts for the yellow rocker switch appear to be ok.
Took a length of wire and noticed when I connected two of the wires in the rocker switch, the low beam headlight switch Es on..
I Have a few questions.
I can confirm there is power at the lh side switc h. J
Does that mean that all other components in the headlight circuit are ok?
Is there a relay I should check?
I will have another look at the Left hand switch and try to remove the yellow switch so I can have a closer look at the five pins.
One of the wires I short circuited to get the headlight working was the one referred to in was80's repair post.
I will report any findings a sap.

Gabriel, Melbourne Australia.

m mm J

;BMW; 1984 BMW k100..frame number 6228?

9Back to top Go down    Re: Low beam headlight not working! on Thu May 19, 2016 4:07 pm


Life time member
Life time member
If your high beam is working but not low then you can do a workaround by having a normally closed relay go to the low beam triggered to open when the high goes on.

I don't recommend this but it did work for me when I needed a quick fix right before a long ride. (The headlights were relayed so the normally closed relay did not have to take much of a load.)

Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R

10Back to top Go down    Re: Low beam headlight not working! on Thu May 19, 2016 5:26 pm


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thats a bugger Gabriel .
During the recent recovery of Blue from our little mishap , I did a little fiddling with the switches .
I found that with some careful rocking of the LH switch , the low beam became active .
So contrary to my first thoughts , the problem lay in the left switch block.
have a look atthis

1987 K100RT Ex- police
1989 K100LT Ol' Blue and "Kart" the Kamper trailer. now KAPUT .
1993 K1100RS 0194321 Colour #690 Silk Blue aka" Smurfette"

11Back to top Go down    Re: Low beam headlight not working! on Fri May 20, 2016 9:00 am


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Hi Gabriel, not sure what groverK has shown you in the post above as the link didn't work for me but from the conversations above I also think your problems will be in the left switch block.

Once you take it apart you will see a section of plastic (or bakelite as some of us old blokes might call it) that is the moving section of the switch - it is moved by the yellow Hi/Lo/Flash button. Mounted on the side of that section are two contacts; one shaped like a stirrup and the other like a stirrup bent at 90deg. Beware they both have springs under them.

I have repaired a couple of them for friends as well as my own K1100 switch which I wrote up. The ones I have repaired for others suffered from the two moving contacts having worn and burned - also the plastic surrounding them was damaged from the heat.

I have attached a couple of poor quality photos of these bits that may help if you haven't got in this far already.

If you're got a steady hand using silver solder you may be able to repair the contacts (if that's the problem). The silver solder will be hard enough to last quite well.

Good luck with it.

95 K1100LT 0232224; 90 K75 6427509; 87 R80G/S PD 6292136

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