Wiring for small BMW MotoMeter - duhme

Discussion in 'Airheads' started by semoir, Jan 2, 2012.

  1. semoir

    semoir aging_hooligan

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    Small tach (below).

    Some scribbled wire color codes (?) on rear of it. Trying to track down which wire goes where and it's rapidly turning into a PITA. Knowing 4 is grd, any help with what goes to pins 1 thru 3?

    I'd hate to toast it..

    Kudos & HNYr


    .[​IMG]......................[​IMG]

    .
    #1
  2. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Tachometers only need +12V, Ground, and a signal from the coil.

    Take a closer look at the terminals - the area around them - and you may see some numbers either in the plastic or stamped in the metal housing. Normally these things are labeled.
    #2
  3. disston

    disston ShadeTreeExpert

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    What vintage machine is this supposed to fit? It should show on wiring diagram if you know what it came out of.
    #3
  4. Wirespokes

    Wirespokes Beemerholics Anonymous

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    These are an optional part for tachless bikes like the R80G/S.
    #4
  5. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Yep, they're pretty fanatical about DIN 72552. A 31a always does the same thing.

    http://www.isham-research.co.uk/quattro/wiring/Typ85/terminals.html

    And the color coding is defined by DIN 47002. Used to have a copy of that color chart and/or knew where there was an online one was but I can't find it.

    That "ground" is just an impromptu case ground so that the lamp would work. Nothing to do with the counting of tachys.
    #5
  6. semoir

    semoir aging_hooligan

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    Disston -- it’s out of a ’89 GS w/PD kit.

    Wirespokes -- so yes, It's probably that optional tach for the early GS’s. I did see the stamped terminal designation after a closer look; shown in my photo above #1 is for hot 12V, #2 Grd, and #3 is for Z (signal).

    Bill -- yes I see #4 is that impromtu case grd (screw).

    Anyways, after screwing with it this afternoon, dosn't look like it's gonna work. I do note a couple of the terminals (1 & 2) are sloppy loose so it’s probably in need of repair.

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    Wirespokes, do you work on these things (I note your sig)? Shoot me a PM if you do, or if anyone has any suggestions re a shop to check it out/repair would be appreciated. Probably a scarce piece. It's going in the hole working, or not. (preferably working)

    <o:p></o:p>
    Thanks all for the help .. appreciate it.
    #6
  7. Wirespokes

    Wirespokes Beemerholics Anonymous

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    I have gotten them working before but don't have replacement electronics if that's kaput. I'm definitely willing to take a look and if I can't get it working, won't charge you anything. You'll only be out the shipping.

    The speedo shop here in town doesn't fix electronic tachs and referred me to a shop in the Bay Area. I believe the quote was something like $180. :eek1
    #7
  8. Boxer Metal

    Boxer Metal Mad Scientist

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    Take a clearer and bigger picture of the back and I'll tell you which wires go where and the color code.
    #8
  9. semoir

    semoir aging_hooligan

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    Wirespokes -- I'm thinking I'll poke around with it for a while (praying), then contact you (prior to smelling smoke). Nothing at this time smells burnt ... Kudos.

    bmweuro -- here you go. Any ideas appreciated .. someone said they are pretty much bullet proof ... fingers are
    crossed it's just the wiring. I'm assuming "Z" is the coil .. the sender.

    Thanks again...

    [​IMG]
    #9
  10. Boxer Metal

    Boxer Metal Mad Scientist

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    + = Green wire with a black stripe. This will be a wire that is only hot when the ignition is on. You can tap into any of these wires on the bike.
    - = Brown wire which is a ground. You can add a wire and ground it to one of the coil mounting bolts.
    z = Black wire on the points side of the coil. Follow the the wire from you points or the black wire from your electronic ignition to the coil and plug it there. You can run a gray wire with a black stripe from your park light to the light on the tachometer.
    #10
  11. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    +, - and z. I think 'Euro's got it.


    And those terminals look like 3/16"/4mm Fast-ons, so you can get crimp terminals for them.
    #11
  12. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Yep, Z is the signal. Good luck and hope it works! These are cute tachs!
    #12
  13. fishkens

    fishkens Long timer

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    I bought one of these tachs with my '88 GS and it failed w/in a couple of months. The warranty replacement has now worked for over 20 years. I've read here that they were prone to failure. Who knows?

    Bottom line is that there may be a few dead tachs like this floating around so that may be the problem.
    #13
  14. semoir

    semoir aging_hooligan

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    Thanks bmweuro -- all wires accounted for. Continuity checked and double checked on each .. and dayum, still no workie. Checked and double checked. It dosn't seem to be the hook-up as I can tell. Assuming prob must be in the guage .. as mentioned a couple of the terminals are sloppily loose. Did accomplish loosing all the instrument lights. Now will search that out .. (argh .. tight spaces inside the GSPD instrment/light fairing). No pin fuses blown.

    Bill - thanks. Re "fast-on" terminals, meaning that they can be replaced? duhme

    Yes, cute little tach wirespoke. I hate it not working and I really don't want to replace it with a non-oem. So for now it's got me in a corner. If it can't be looked at (opened up to check those loose terminals, etc) guessing it'll go backin the hole inoperatable. Maybe after my rtrn from the LVegas auction next week I'll shoot you a PM, perhaps have you take a look at it. I'm stumped.

    fishkins -- you're right, I've heard they're near indestructable. I'm hoping to retreive it somehow.

    Again, thanks all for the help. It's appreciated ..
    #14