R90S taillight problem

Discussion in 'Airheads' started by hardwaregrrl, Apr 7, 2012.

  1. hardwaregrrl

    hardwaregrrl ignore list

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    Hey all I'm working on a friends bike. I have a taillight at the halfway position on the ignition switch but fully on its gone. I also have an orphan wire on the fuse panel far left side 4th from the top. It's a black/grey wire. I have nO idea where it belongs. Where do you get a schematic of the panel?? Tia

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    #1
  2. melville

    melville Long timer

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    Blaine posted this in my thread:

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    Grey mit black tracer looks to be the hot for the taillight, parking light and instrument lights. If it's loose and has a straight terminal, and not an insulated flag terminal, check the parking bulb in the headlight.

    I don't see a black mit grey tracer, but there's a black, white tracer that goes from the TS relay to the TS dash indicator.

    Good luck!
    #2
  3. wirewrkr

    wirewrkr the thread-killer

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    Jenna, we need to know the year and model before diagnosing and before posting a schematic. Keep in mind (Melville and Blaine) that the schematic Mel posted is for a 1 year only bike. It seems like every time some one posts a query on a wiring problem, that schematic pops up from somewhere. That is the LAST one I would use a s a general example of wiring.
    Jenna, do you mean a grey with black tracer? That color is for the parking/taillight circuit on all models. Never seen a black/grey on a BMW.
    #3
  4. Jim K in PA

    Jim K in PA Long timer

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    Just came in after looking at my tail light assembly (bulb was out). Gray/black is the tail light wire on my '79 100T. What is odd that yours goes out in the run position. I suspect that the orphaned wire is plugged in to the terminal for your tail light wire, but put a meter on it and see if the wire is hot and in which position. The city light in the head light bucket on my 100T is only hot in the first position, off in the run position. Methinks some one mucked about and swapped the tail light connector with the city light connector on the board. They should be close by each other, but I don't have a diagram.

    If the orphaned wire is the city light wire, it's other half should be attached to the main headlight harness.

    Not sure if this made any sense to anyone but me . . . :huh
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  5. hardwaregrrl

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    I Get it! City light being what I would call a parking light.


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  6. hardwaregrrl

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    76 R90S It;s the bare wire in the center of the pic which I guess is grey??? Black tracer being the stripe?


    #6
  7. bmwrench

    bmwrench Long timer

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    It's Grey/Black. The other end of it is plugged into the park cicuit, as it should be. Does the bike have a park bulb in the headlight? Is it missing it's wire?

    The tail light is powered by the headlight relay when the ignition is "on" on '75 on bikes. (Thats a lot of "ons", ain't it?). This is a double pole relay, so even if the headlight works, it is possible for the parking and tailghts to not work.
    #7
  8. wirewrkr

    wirewrkr the thread-killer

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    Since that bike is a 76, don't use the posted schematic, The 74 didn't use a headlight relay and the wiring is way different
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  9. wirewrkr

    wirewrkr the thread-killer

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    Correct Jenna, the predominant color on the wire is always the first one in the description, ie, Grey with a black tracer, or, Grey/black, or grau/schwartz

    By the way, there seems to be some seriously overheated wires in there.
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  10. hardwaregrrl

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    Yeah I know. There is one or two that go to the headlight relay that have tried to shed their skin. You should see the hi/low switch. I dont think I took a pic of that, somebody cut the yellow wire and spliced it in with the red wire.:huh I'm not sure why....but he has ordered a new switch. His high beam never worked. Wonder why! I'm wondering if that's why the red wire is so heated looking??
    #10
  11. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    PO wiring. Ugh.

    The Germans are very organized and have a standard for everything, the DIN (Deutsches Institut für Normung). Every color code in the wiring means something specific, and is the same for every vehicle. Red is an always-hot wire from the battery. Yellow is the headlight low beam. Grey-black is a taillight. And so forth (USW). And the color names are in German-- Red is Rot (abbrev RT). Yellow is Gelb (GE) Gray-black is Grau-schwartz (GR-SW).

    I have no idea how the new-fangled CANBUS has mucked up the color coding. :(

    Same deal with the terminal designations on switches, relays, etc. A relay 87a always does the same thing.

    I've misplaced my .PDF and Web link to the DIN automobile color codes, but here is a text file of the terminal codes:

    Code:
    Ignition system
    1 coil, distributor, low voltage
    1a, 1b distributor with two separate circuits
    2 breaker points magneto ignition
    4 coil, distributor, high voltage
    4a, 4b distributor with two separate circuits, high voltage
    7 terminal on ballast resistor, to distributor
    15 battery+ from ignition switch
    15a from ballast resistor to coil and starter motor
    
    Starter
    50 starter control
    
    Battery
    15 battery+ through ignition switch
    30 from battery+ direct
    30a from 2nd battery and 12/24 V relay
    31 return to battery- or direct to ground
    31a return to battery- 12/24 V relay
    31b return to battery- or ground through switch
    31c return to battery- 12/24 V relay
    
    Turn indicators
    49 flasher unit in
    49a flasher unit out, indicator switch in
    49b out 2. flasher circuit
    49c out 3. flasher circuit
    C 1st flasher indicator light
    C2 2nd flasher indicator light
    C3 3rd flasher indicator light
    L indicator lights left
    R indicator lights right
    L54 lights out, left
    R54 lights out, right
    
    AC generator
    51 DC at rectifiers
    51e as 51, with choke coil
    59 AC out, rectifier in, light switch
    59a charge, rotor out
    64 generator control light
    
    Generator, voltage regulator
    61 charge control light
    B+ battery +
    B- battery -
    D+ dynamo +
    D- dynamo -
    DF dynamo field
    DF1 dynamo field 1
    DF2 dynamo field 2
    U, V, W AC three phase terminals
    
    Lights
    54 brake lights
    55 fog light
    56 spot light
    56a headlamp high beam and indicator light
    56b low beam
    56d signal flash
    57 parking lights
    57a parking lights
    57L parking lights left
    57R parking lights right
    58 licence plate lights, instrument panel
    58d panel light dimmer
    
    Relay
    85 relay coil -
    86 relay coil +
    Relay contacts
    87 common contact
    87a normally closed contact
    87b normally open contact
    88 common contact 2
    88a normally closed contact 2
    88b normally open contact 2
    
    Maybe 'Wire or sombody has the DIN color codes handy.
    #11
  12. Wirespokes

    Wirespokes Beemerholics Anonymous

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    I'm sure I could find the color code for the wires, but I rarely use it. Brown is ground, red is hot, etc. And the wiring diagram - that's mostly what I get manuals for.

    So, you can't find the other end of that wire?

    I think wiring and electrical are the hardest things for people to understand - as evidenced by the 'repairs' I've had to deal with. A bike may look pristine, but guaranteed the wiring will be mucked up! :lol3

    What tends to happen is the headlight switch shorts out (not exactly sure why) and fries the wiring, and the switch is toast. It may have something to do with the always hot 'flash' function, or that full headlight current passes through the switch. Supposedly the way to help save these switches is to wire in a headlight relay, but it's tricky fitting one more thing in the headlight bucket! Been there, done it, got the T.

    My wiring diagram for the 76 shows the Gray/black wire going straight to the tail light from the second fuse.
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  13. hardwaregrrl

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    The weird thing is that I had the taillight working a few weeks ago. I've been focused on the m/c and calipers for the past few weeks. I went to ride the bike back to him yesterday and discovered the taillight was out. Before i had just cleaned all connections and everything was cool.

    The only thing I did that could have caused turmoil was to remove the yellow wire from the red in the switch. I've since resoldered it just until he gets the new switch. I'll snap a pic of that and post it just because...
    #13
  14. melville

    melville Long timer

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    Put it under the tank. Go to post 131 et al.

    The switches cost $180. The relay costs $30ish.
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  15. hardwaregrrl

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    FYI the bike is a 76 and does have a working, factory relay.
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  16. hardwaregrrl

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    Hey Melville, thanks for the info. I may replace the original relay with the one you used. I'm not certain my test proved that the relay does work since I cannot get the hi beam to light since the switch is buggered.
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  17. melville

    melville Long timer

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    This was actually adding another relay to handle the dip function with a semi-functional buggered switch. Again, switch $180, additional relay $30. One needn't be a KLR rider to understand that math. My switch was buggered mechanically, in that it wouldn't hold the high beam position. If the switch you are working can make momentary contact, like, say, the "passing beam" function, this fix will work for you.

    The stock relay in the shell doesn't factor in the HI/LO decision.
    #17
  18. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Yep, I know all the "usual suspects", too, but I had that chart at one time. It's useful for neophytes to become indoctrinated in the DIN. :eek1

    Wiring can be a royal PITA, agreed. You have to have an innate feel for it, and an inborn sense of electrical elegance.
    #18
  19. hardwaregrrl

    hardwaregrrl ignore list

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    So, I basically hit all the spades on the board with a test light to determine which ones have power when the ignition switch is fully on. I know that the taillight worked a month ago, and I did not move anything on the board. Is there any other way a spade could have "flipped"? I mean, the spade it was on had power at the "city light" turn, but lost power at the full turn on the ign switch. I swear I never moved the wires around. So I just swapped to an open terminal that had the appropriate power.

    I've never had an airhead with the board in the headlight, so just want to cover my ass and make sure I havent done anything to harm the wiring. thx
    #19
  20. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    The headlight bucket has the appearance of a can o'worms, but it really isn't. Break it down into _related_systems_. Copy the wiring schematic. If you can use a copier that enlarges, enlarge just the headlight bucket wiring. Highlight just the headlight wiring (and the tail light since they are related), and highlight each function in a different color to separate them. That will make tracing out the headlight wiring much easier.

    Do the same thing for the turn signals/brakelight/horn, and ignition/starting/charging, and so forth on separate copies of the wiring diagram.
    #20