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Thread: R90 electrical gremlins

  1. #1

    R90 electrical gremlins

    I picked up a 1976 R90 a few years ago and have been going through it replacing rubber bits and refreshing parts a little at a time the bike runs great and I love riding it. The original owner passed on a few years ago and I picked it up from a friend of his. It had a large fairing when purchased new and he removed it before I bought it. The front signal stems had been clipped off so I picked up some new stems wired and installed the front signal lights.
    So the problem is the lights flash and work fine but I have found that they also work with the ignition key turned off so they alays are powered This I can live with but the dash light remains steady on when the key switch is off. I should mention also the fourway flasher switch was toast so I unplugged and removed it as they are NLA not sure if that is relevent or not although the four way switch dash type light always remained on also unless I pulled it up enough to disengage it from its harness but now the signal dash light remains on.
    Sorry for the long winded thread.
    Any ideas of where to start on sorting out this problem.

  2. #2
    Registered User Guenther's Avatar
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    Does ANYTHING turn off with the ignition switch in OFF position? Can you start the motor in OFF position?

    /Guenther
    Last edited by Guenther; 03-27-2020 at 02:46 PM.
    2017 F700GS

  3. #3
    Registered User STEVENRANKIN's Avatar
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    Circuit board

    One of the fine things about BMW is they put the circuit board everything is plugged into in the headlight. Great for weather protection, not so for working on it.

    I bet if you get a good light and move wires around a bit, you may find you have one of your connections plugged into the wrong spot on the board.

    Best to have a good schematic with color and patience to work in the restricted space. I have plugged things into the wrong slot by accident due to my vision and fat fingers. Unless, the wiring has been changed or compromised and is still factory, it is all color coded. Just hard to see in the headlight. A bundle of snakes.

    As for the four way flasher switch, it might be worth giving Mark Huggert in Switzerland a call. Or if not them one of the British or European parts dealers. Mark Huggert was able to get me a NLA in America part. A phone call is cheap. As I don't have a schematic handy right now, I cannot say for certain taking the flasher switch out would cause problems or not. I would think not as it is mostly a separate circuit.

    It would be so nice to take all the guts out of the headlight and work on it with extra room, oh wait! BMW did that in the 1985 and newer bikes!. Does not help us with older bikes. LOL. St.

  4. #4
    As with anything like this, check the work you did against a wiring diagram. It seems unlikely that it would have been this way for the PO. And as I write that I am viscerily reminded of the wiring nightmare on my R100 when I bought it used.
    '61 Clubman's Gold Star, '13 690 Duke, '13 Daytona 675R, '18 Street Triple RS, 2020 R1250R (gone but not forgotten: '76 R75/6, '84 R100, '76 R90S)

  5. #5
    Registered User STEVENRANKIN's Avatar
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    Previous owners

    When I bought my first BMW bike, it had a Pacifico fairing on it. Ugly as sin, so, I let the previous owner keep it and he in turn let me do the wiring for the stock lights. Or, at least that was the deal. When I picked up the bike, he had "rewired" the lights.

    It took me a couple of days to figure out what he had plugged in wrong and had in the wrong place. Thank goodness for schematics and patience.

    Now I have the schematics, but not the patience. St.

  6. #6
    Everything else works as it should. I will check the connections and make sure they are in the proper place on the board. I do have good wiring diagrams its just hard getting my fat fingers in there and trying to move wires around to see where everything is.
    Hoping its as easy as just having connections in the wrong place.
    I have owned several BMW bikes over the years and enjoy doing all my own work but electrical has never been one of my strong points.
    I will take a look today and report back.

  7. #7
    Registered User STEVENRANKIN's Avatar
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    Fat fingers

    Join the crowd and welcome to the fat fingers brotherhood. LOL

    Don't worry about posting a long thread, the more information you can put in the question is better. Better yet is when pictures or video are added. St.

  8. #8
    Well I spent some time today making sure all the wires were in the proper place and according to the diagrams I am working from they are although I did have to relocate one wire for the front right signal. The problem remains the signal flasher light on the dash remains dimly lite when ignition is off. I just pull the ground cable off and on as I work. Everything else works as it should signals work and flash front and back and the dash light flashes along until I turn them off but still get a dim steady light on the dash. I did take apart the throttle to clean and grease it could I have mucked the signal switch up or maybe pinched a wire in the switch?
    This is leaving this fat finger member a little frustrated.

  9. #9
    Registered User STEVENRANKIN's Avatar
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    Oh sorry

    I am sorry to hear it is not an easy fix.

    You did say you at one time had four way flashers installed on the bike and they were the. factory ones?

    There may be a possibility the four way flasher relay is feeding into the circuit somehow. I am NOT familiar with the R90 Electrics so I am guessing. On my 78 R100RS, the turn signal indictor light would flash as well as the four way flasher switch when the four way flashers were in use. There its a lead from this relay to energize the indicator light as there is in the normal turn signal flasher relay. Perhaps, there is a line there that is out of place or no longer needed that is supplying voltage to the light?

    Snowbum, the BMW guru has a wiring diagram on his site for the four way flasher system. Forgive me, I don't know exactly where in his site (it is pretty extensive). From my own experience, in troubleshooting four way flasher system, The four way flasher system WAS NOT included in any of the wiring schematics I had on hand. Only by printing out a copy from his site was I able to make sense of how the four way flasher system ties into the regular electrical system.

    Also, when looking for a problem, don't neglect the ground wires, Pretty much brown is ground but, there may be a surprise in a brown other color combination. Again, I don't have a schematic handy so I may be talking nonsense about the brown and other color combinations. I think what I mean is not only look and see where the wires go, think about the function of the wire.

    Right, the last bit was clear as mud. Relays, sometimes have numbered connections, or even a diagram of the internals. Use that with the schematic to figure out if power is going where it should an in some cases in the proper direction. Not sure if there are any diodes in the system allowing current flow in one direction or not, they can make a difference.

    Ok, I am done rambling, sorry I cannot be there to help. St.

  10. #10
    Registered User Guenther's Avatar
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    Did you install LED turn lights?

    How many connectors for the turn light relay?

    /Guenther
    2017 F700GS

  11. #11

    four-way relay

    After inspecting the fourway flasher relay under the tank it is in pretty rough shape it is a 15AMP and has four spade connecters of wich two are loose and wiggly, could this be the problem? When I disconnect the red power wire to this relay the signal light system shuts down. after a little research BOBS has them listed for $55.00 so kinda looking for a substitute if possible I believe it is a bosch #61321358198
    I also started a thread on Beemer airhead site looking for help, any suggestions are very much appreciated.

  12. #12
    Registered User STEVENRANKIN's Avatar
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    Could be

    Well, a crudy rusty relay with wiggly wires is not a good thing to have. LOL.

    I cannot say for certain you have solved the problem but you are on the right track it sounds like.

    You do realize, if you are NOT going to use the four way flashers at all (I recall you saying the switch was toast and NLA?). you can take the four way flasher unit out of the system. You do need to have a good schematic and patience. If I recall, the four way system was an add in to the overall system. So, If you find the right connections, you can pull the whole shebang out of the system and still have the stock turn signals and such. Snow Bum has a four way flasher system wiring diagram somewhere in his website.

    I mean, if you are not going to use the four ways, why spend the money on a relay as well as have extra wiring in the system to corrode and cause problems? The turn signals system does not need the four way system to work.

    Do you get what I am writing?

    As to a suitable replacement non BMW part, you may be able to use the Bosch number at a local auto parts store to cross reference to a non BMW part. I do know there is a list of stuff like this in existence in the Airhead, and other BMW communities.

    Also, if you would like to replace the switch, email around to other dealers, and give the Swiss Mark Hugget or UK Motobins an email. Sometimes the UK or European shops have parts in stock that are NLA here.

    Sorry I can't be more help, If you were nearby, I would be happy to lend a hand. St.

  13. #13
    Registered User STEVENRANKIN's Avatar
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    Oh by the way

    Oh by the way, if you read any of my posts in the forum, you will realize I am far from perfect. I have fat fingers, and little patience, but for the most part get things fixed. LOL. St.

  14. #14
    Registered User Guenther's Avatar
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    Four way flasher relay (5 spades) is not the turn light relay (4 spades).

    Do you have the four way flasher (for hazard light) relay installed?

    /Guenther
    2017 F700GS

  15. #15

    relays

    The turn signal relay inside the headlight bucket is new last year. The relay that in connected to the four-way system is under the tank and has 4 connection spades on it. I do have snowbums four-way diagram but have not had time to go through it on my bike but will shortly. This should allow me to track down and compare the wiring on my bike. The switch at the hadlebars is sticky getting in from on to off but still works so have not decided on keeping the four-way system or removing the whole thing.
    I will post my results.

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