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Thread: 1979 R65 (American) issue with headlight electrical.

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  1. #1
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    1979 R65 (American) issue with headlight electrical.

    Ok guys -- seriously having a nervous breakdown with the R65 (1979 vintage). I have deduced that the relay receptacles are wonky for the light relay and the indicator relay. If I plug in the relays and jiggle them around, I eventually get the indicator buzzer to work and the front head light lights up. When I start the bike, the headlight turns off as is proper (during the crank to send all juice to the light), but the light is always on, from the moment I plug in the light relay until the time I turn it off. Does anyone know what tells the light to be off when the key is not on or the bike is not switched to start? Also (on a side note), what is the best way to fix the relay receptacles? This is absolutely killing me :-( Thank you in advance!!!

  2. #2
    Rally Rat
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    light always on

    The light is shut off while cranking by the starter relay. Check there first and you'll see on the wiring diagram where a wire goes to the headlight relay from the starter relay, which provides a ground. When starting, this wire becomes "not grounded", thus causing the headlight relay to not operate.
    Boxerbruce

  3. #3
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    Quote Originally Posted by 1074 View Post
    The light is shut off while cranking by the starter relay. Check there first and you'll see on the wiring diagram where a wire goes to the headlight relay from the starter relay, which provides a ground. When starting, this wire becomes "not grounded", thus causing the headlight relay to not operate.
    Thanks Bruce. I think that's working right :-) The problem I'm having is that the headlight stays on all the time. the only way to get it to go out is to pull the relay (or crank the bike during which it goes off during the crank like it's supposed to -- right?)

  4. #4
    Registered User boxerkuh's Avatar
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    Let me say that I am not a mechanic or an electrican. However, I have had the same problem before and it turned out to be a bad relay. I attempted to replace it with a "local" relay purchased at Auto Zone, and although I made sure it was hooked up right, it did not work properly. I ended up ordering a BMW relay and all was good. I did take it apart and say that one of the diodes was burned up. With a 79 that is reasonable.
    Keep the rubber side down!!
    1986 R 80 RS
    1992 R 100 R
    BMW MOA Life member; Ironbutt Member; Airhead Member

  5. #5
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    Quote Originally Posted by Boxerkuh View Post
    Let me say that I am not a mechanic or an electrican. However, I have had the same problem before and it turned out to be a bad relay. I attempted to replace it with a "local" relay purchased at Auto Zone, and although I made sure it was hooked up right, it did not work properly. I ended up ordering a BMW relay and all was good. I did take it apart and say that one of the diodes was burned up. With a 79 that is reasonable.
    I just re-posted to see if I could get any more responses but I am going to try another relay. BMW has ordered two relays (both wrong) and I think I have the right part and pin out now so I'm going to give it another shot before I complete pull my hair out! Also, of note, the relays I have are manufactured in 11/78 and they do not appear to show a diode in the schematic, but they do appear to be original BMW parts.

  6. #6
    Registered User lmo1131's Avatar
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    mmm m m m m...

    I just re-posted to see if I could get any more responses but I am going to try another relay.
    Just an observation ... rather than "re-posting" in an attempt to gather more input, keep adding to your original post. It does the same thing; brings the post back to the top of the page -plus- it also maintains a continuous thread which is helpful when referring back to the topic.

    Give Motorrad Elektrik a call. I can't think of anyone who knows more about airhead electric bugs than Rick does. I'm sure he's heard of this problem before.

    EDIT - Starter relays are in the "Chassis" section (for some reason ).
    Last edited by Lmo1131; 01-13-2013 at 08:34 PM.
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

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