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Thread: Lighting Problems

  1. #1
    Registered User pandry1's Avatar
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    Lighting Problems

    I'm about 80 percent finished with my 1974 R75/6 resurrection project. I took it for a ride yesterday evening and discovered that the tail light and spedometer / tach. lights were out, but the brake light works. I changed the rear bulb - still no tail light - and no lights on my spedometer / tach. However, when I turn the key to the "park" position, I get instrument lights and a tail light. The previous owner changed the ingition key assembly (lost the keys) before I acquired the bike. Could it be that some of the wires on the ignition assembly are reversed?

    Also - when I activate the turn indicators, the instrument pannel light (yellow one at the bottom) flashes only once, then stops - both the front and rear flashers continue to work fine. Occasionally the pannel light will continue to work if I turn left (?), but not very often - engine has to be at higher rpm. Wrong bulbs? Bad flasher?

    Note: still looking for an inexpensive replacement headlight assembly from shell forward. I've temporarily used a Vetter fairing headlight bulb - held in place with some rubber insulation. The little headlight parking light is not hooked up - should that make a difference?

    Any advice will be greatly appreciated - I've not run across these gremlins!

  2. #2
    Administrator 20774's Avatar
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    RE: speedo/tach/tail lights. According to Haynes, all of these get power through one fuse. Since you get these to light when in the park position, that seems to indicate that the fuse is OK. Only one power line comes into the fuse...diagram shows a gray one. This one gray wire comes from the ignition switch. Both the park (P) and engine running (3) part of the switch feed power to this gray wire. So, it would seem that there's something wrong with the ignition switch wiring.

    Parking lamp shouldn't be a problem...it gets power from the same fuse as above and then goes to ground...no other circuit should be affected.

    Not sure what to say about the turn signal. Front and rear signals operate through the same fuse and power comes from the handlebar switch which in turn gets power through the turn signal relay. I'd start by checking all bulbs with an ohmmeter or hooking them up directly to the battery with some small wires. If those are OK, check the grounds at each of the front bulbs...they should ground right there. The rear bulbs seem to be grounded through a larger circuit, not at the bulbs. After that, I'd look at a new relay. But check the easy, no cost stuff first.

    Try Airhead Salvage for a new front headlight assembly.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Registered User pandry1's Avatar
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    Wiring Color Order

    O.K. - I removed the headlight and am looking at the switch on the right. There are four posts on the bottom of the switch, and one on the top. The first post (closest to me) has the referenced gray wire attached. The next one back has a red wire attached. The third one back has nothing attached. The fourth one in the back has a yellow and white wire attached. The post on top has a green wire attached. Is this correct? I do not have a diagram and can not determine function with an ohm meter(???). If anyone has a diagram, please let me know if this is the sequence. If not, please let me know what it should be... I've tried to find a diagram on the net, but no success to date.

    Thanks!

  4. #4
    Administrator 20774's Avatar
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    Haynes has the following per the numbered terminals; I don't know what's front or back:

    - #30 -- red
    - #15 -- green
    - #58 -- gray
    - #56 -- yellow/white

    On the BMW electrical CD, the yellow/white wire is shown as a green wire. The /7 ignition switch is wired the same way, with two green wires, not the yellow/white wire.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
    Registered User pandry1's Avatar
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    On-going Wiring Problems

    O.K. - so I made a schematic of the five conectors on the new three way ignition switch - four on the bottom and one on top. I used an ohm meter to determine which tabs were connected in the off, park and run positions. Using the schematic, I re-wired the switch. I then purchased a second hand light assembly, bulbs, etc. and got (almost) everything connected. I have an extra grey wire with black stripe coming out of the harness to the headlight bulb - any ideas what this powers or is supposed to connect to? I had to make an extra "jumper" wire to connect the ignition switch's foward most connector (of the four bottom connectors) to the small parking light in the headlight assembly. This pole is hot only in the park position - now the front parking light works in the park position. but goes off in when the switch is in the run position - great! However, my tail light doesn't work with the switch in the park position - but it does work in the run position. Any ideas would be appreciated... Oh - I did try hooking up the grey wire with black stripes to the front (small) parking light. This made the parking light come on in the park and run positions(?).

    Summation: I have an extra grey wiire with black stripe that is not connected to anything - and my tail light does not work in the park position. All other lights work as they should - not a bad problem, but I would like to get it right...

  6. #6
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    identical problem

    I have this exact problem on my 1984 R65. I don't understand what is supposed to energize the instrument lights and tail light when in the start/run position. Both work in park, but not when I want to start and drive the bike!

  7. #7
    Administrator 20774's Avatar
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    Quote Originally Posted by jtatknox View Post
    I have this exact problem on my 1984 R65. I don't understand what is supposed to energize the instrument lights and tail light when in the start/run position. Both work in park, but not when I want to start and drive the bike!
    The only thing I can see as a difference between the park and run position on the ignition switch is that when in the run position, the light relay becomes part of the circuit. So my guess there's something wrong there, bad connection, etc.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  8. #8
    Monza Blue 1974 R90/6
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    I have a 1974 with european switches.

    In the first "on" position,

    Tail light - on
    Brake Light - not energized
    Blinkers - not energized
    Small bulb in the headlamp - on
    Head light - not energized
    Starter - not energized
    Horn - not energized

    Dashboard
    Instrument illumination - on
    Neutral - not energized
    Oil - not energized
    Gen - not energized
    Turn signals - not energized
    Brake fluid - not energized

    This is a comon "parking light" feature for european vehicles. You can take the key out of the ignition in this position.

    It sounds like your bike is working exactly correct with the switch in this position.


    Turning the switch to the next (second "on") position:

    Tail light - off
    Brake Light - works if you step on or pull in the brake
    Blinkers - work if you flip the switch
    Small bulb in the headlamp - off
    Head light - off
    Starter - works if you press the switch
    Horn - works if you press the switch

    Dashboard
    Instrument illumination -off
    Neutral - on
    Oil - on
    Gen - on
    Turn signals - on if the switch is flipped
    Brake fluid - on if fluid is low

    Note - can't take the key out of the switch in this position. I would describe this switch position as "driving without lights".


    Turning the switch to the next (third "on") position:

    Tail light - on
    Brake Light - works if you step on or pull in the brake
    Blinkers - work if you flip the switch
    Small bulb in the headlamp - on
    Head light - off
    Starter - works if you press the switch
    Horn - works if you press the switch

    Dashboard
    Instrument illumination - on
    Neutral - on
    Oil - on
    Gen - on
    Turn signals - on if the switch is flipped
    Brake fluid - on if fluid is low

    Note - can't take the key out of the switch in this position. I would describe this switch position as "driving with parking lights". Basically, everything is energized except for the head light.


    Turning the switch to the final "on") position:

    Tail light - on
    Brake Light - works if you step on or pull in the brake
    Blinkers - work if you flip the switch
    Small bulb in the headlamp - off
    Head light - on
    Starter - works if you press the switch
    Horn - works if you press the switch

    Dashboard
    Instrument illumination - on
    Neutral - on
    Oil - on
    Gen - on
    Turn signals - on if the switch is flipped
    Brake fluid - on if fluid is low

    In this final switch position everything is energized except for the small bulb in the headlamp. I would describe this switch position as "driving with lights".

    Does that help you any?

    Could it be that your bike is wired for the european switch with positions described above and the previous owner replaced it with a US ignition switch?


    Finally, I think the issue with the turn signals flashing when the switch is flipped but the dashboard blinker lamp only working intermittantly is a separate problem from the operations resulting from the ignition switch positions.

    Regards,

    Barron
    Last edited by Barron_Williams; 08-20-2012 at 01:17 AM. Reason: Final thought

  9. #9
    Registered User mneblett's Avatar
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    Quote Originally Posted by pandry1 View Post
    O.K. - so I made a schematic of the five conectors on the new three way ignition switch - four on the bottom and one on top. I used an ohm meter to determine which tabs were connected in the off, park and run positions. Using the schematic, I re-wired the switch. I then purchased a second hand light assembly, bulbs, etc. and got (almost) everything connected. I have an extra grey wire with black stripe coming out of the harness to the headlight bulb - any ideas what this powers or is supposed to connect to? I had to make an extra "jumper" wire to connect the ignition switch's foward most connector (of the four bottom connectors) to the small parking light in the headlight assembly. This pole is hot only in the park position - now the front parking light works in the park position. but goes off in when the switch is in the run position - great! However, my tail light doesn't work with the switch in the park position - but it does work in the run position. Any ideas would be appreciated... Oh - I did try hooking up the grey wire with black stripes to the front (small) parking light. This made the parking light come on in the park and run positions(?).

    Summation: I have an extra grey wiire with black stripe that is not connected to anything - and my tail light does not work in the park position. All other lights work as they should - not a bad problem, but I would like to get it right...
    The gray w/black stripe wire IS the parking bulb in the headlight, and it is normally powered in both the Park and On positions (i.e., it burns when the headlight is on, too).

    The turn signal indicator being on all the time, and the "works when turning left" are suggestions that the problem with the parking lights/turn indicator/tail light are all related by a common failure in the harness. You really need to invest in a Haynes to follow this!

    The turn indicator and speedo and tach illumination are on a common ground circuit. The illumination bolbs are also on the tail light/front parking light circuit (58). BMW does a lot of crafty wiring in which one circuit or component is used for mutliple functions by clever "backwards" feeding of 12V -- for example, on bikes with a Load Relief Relay (turns off the lights during starter motor operation), the lights are turned off by feeding 12V from the starter circuit into the "ground" side of the light supply relay so that the relay "sees" 12V on both sides of the solenoid and disconnects the power feed to the lights. When the starter button is released, the 12V from the starter goes away, so the 12V from the ignition can go to ground and pull in the relay to turn the lights back on.

    I suspect the turn signal circuits have a similar "clever" link to the instrument lighting (and hence to all the lights except the headlight), and that due to a broken or shorted wire in the main harness, the lighting system is seeing 12V or ground through the turn indicator circuit where it shouldn't.

    One interesting experiment would be to turn the left, and when the turn indicator begins working normally, see whether the tail/indicator lights start working normally.
    Last edited by mneblett; 08-20-2012 at 02:34 AM.
    Mark Neblett
    Fairfax, VA
    #32806

  10. #10
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    a clue...

    I think we are getting somewhere with the euro vs. US ignition switch!

    The R65 I have is definitely a euro import with the low bars and had to have the odometer replaced to reflect miles.

    The switch that I installed is a 3 position switch where:

    Off : No terminals connected
    Park : Terminal 30 to terminal 58
    Run: Terminal 30 to terminals 15 and 56 but not 58

    If I connected terminal 58 to terminal 56 or 15 with a diode oriented so that current only flows toward terminal 58 would I then have the operation I am looking for?

    What sort of diode would be appropriate in this case?

  11. #11
    Registered User amiles's Avatar
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    I also suggest that you check fuses and grounds. My experience is with a 1976 model. On my machine The turn signal relay is supposed to alert you to burned out bulb(s) by blinking the instrument light once only when activated, sounds like yours is working properly, I suspect indicating a bad ground. A good cleaning of contact points & connectors cannot hurt.

  12. #12
    Rally Rat
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    A '74 should have a 5-position switch. Unless you add a double-contact relay as used from 1975, the lighting will not work correctly.

    The flasher units in these bikes are suposed to behave as yours does when a bulb is out. They will also do this when the wrong wattage bulbs are used, or when a wire is broken to a bulb.

  13. #13
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    Aay luck?

    Hi Pandry I know its been a while since you posted this but I was just wondering if you solved the problem as I am having the same exact problem on my 1975 R90/6. brake lights work but speedo and tach lights don't. So frustrating any help would be great

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