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Thread: why does the tail light quit working when the turn signal stops working?

  1. #16
    Registered User lmo1131's Avatar
    Join Date
    Jan 2010
    Pismo Beach, CA
    You may have a pinched wire somewhere in the harness, or a wire may be connected to the wrong terminal. The only way to really know is to disconnect every wire in the head light and line test them for continuity. Also check to make sure the wires are connected correctly in the tail light housing and that your ground connections (Brown wire) are solid.

    It sounds like a daunting task, but armed with a wiring diagram it isn't really too scary. Just take your time. If you have a digital camera take some pics before you start and as you go.

    - you might find this Adventure Rider article helpful. Lots of links to reference photos taken during the project. >
    Last edited by Lmo1131; 02-15-2013 at 07:18 PM.
    "It is what you discover, after you know it all, that counts." _ John Wooden
    Lew Morris
    1973 R75/5 - original owner
    1963 Dnepr

  2. #17
    Smoooooth at 430 gch71's Avatar
    Join Date
    Dec 2011
    Katy, Texas

    Question Any updates?

    Did u find the problem for sure or still looking?
    ...driving to work on my airhead
    '73 R75/5, '74 R60/6, '75 R60/6, '80R65

  3. #18
    Registered User
    Join Date
    May 2012
    Quote Originally Posted by Roguetek View Post
    ok, upon some investigation, it would seem my ignition switch is miswired.

    However, instead of having pins 30,30,50,56 ,58 on the back of the switch, I have ( in order) 15, 30, 30, 58, in a row, with pin #56 above the row, in the 11 o'clock position.
    No, the wiring diagram is incorrect. The Haynes and (newer) Clymer manuals have accurate wiring diagrams for the ignition switch in color. As a clarification, the wiring diagram in the resources section for the /7's is 99% correct and I have only found ignition lock wiring errors. It took me a while to figure that out.

    Here is what motobins sells for the igintion lock:

    which has correct connection pin numbers 15,30,30,58 with #56 above and are the same on my original /7 ignition lock. FWIW, I highly recommend getting the Chicago region owners association BMW electrical manual which has accurate (black and white) electrical diagrams along with some sage advice on trouble shooting airhead electrical problems. Here is that link:
    Good luck!

    AH# 13238

  4. #19
    Got a multimeter?

    Check the ground on that taillight. Is it grounding THROUGH THE FLASHER RELAY??? I.e., not grounded unless relay is energized (flasher is on)?

  5. #20
    Registered User amiles's Avatar
    Join Date
    Jul 2003
    Murrells Inlet, S. C.

    Electrical System Chart

    Some time ago at a national rally, Rick Jones of Motorrad Elektrik was selling laminated color charts of the Airhead electrical system. The chart is 12" by about 18". I don't remember the cost. He suggested that I roll it up and keep it in the frame backbone tube which I did.

    These charts are for specific models, not a "one size fits all" situation. The wire colors on the chart are the same colors as on the bike.

    I don't leave home without it.

  6. #21
    Curious if the original poster ever located his problem....?

  7. #22
    Registered User LDB's Avatar
    Join Date
    May 2013

  8. #23
    Registered User kenlavine's Avatar
    Join Date
    Oct 2009
    Western Massachusetts
    Quote Originally Posted by LDB View Post
    That was funny.

  9. #24
    Hey Stan,
    On my R80/7 the turn signals and break light did not work at all.This happened all of a sudden.First thing I checked was the fuse in the headlight bucket.It was loose.I tightened up the connections and signals and break light function.
    1977 R100S, 1978R80/7,1973 R60/5
    1977 Triumph Bonneville
    1970 Triumph TR25W
    1970 Honda CT90

  10. #25
    Registered User helmut_head's Avatar
    Join Date
    Feb 2011

    Ebay has nice diagrams.

    Type in BMW , model#, wiring diagram on Ebay. There is someone out of New England selling large colored laminated ones for $17.00. I bought one and keep it rolled up and onboard along with back probing connectors, an oscilloscope, frequency analyzer, current probe, and timing light.......OK, just joking about the timing light.

    Try Ebay.
    Helmut always wears a Helmet.

  11. #26
    Registered User
    Join Date
    Dec 2007
    Reno, NV
    I had a similar problem on my 1982 R100RT. The connection for the various rear fender lights sits above the battery, and unsurprisingly was very corroded. Cleaned that up, problem solved.

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