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Thread: Electric Windscreen Frustrations - '94 K75RT

  1. #1
    Dum vivimus vivamus ted's Avatar
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    Electric Windscreen Frustrations - '94 K75RT

    Hi Folks,

    I have a 1994 K75RT that I have grown quite attached to, but is starting to show that love is a two-way street

    CAUSE: Last fall I was riding through town and wanted to put the windscreen down, so I hit the down button on the dash pad and down it went. A few seconds later when I went to pop it up just a smidge I realized the button had caught on the foam dashpad in the down position and for about 15 second or so was engaged in the down position with the windscreen all the way down. I popped it up a few inches then went to drop it just a bit and noticed it would no longer go down.

    Fast forward a few months. It was suggested that I might have fried the down relay so I bought a known good one from Drake at kbikeparts.com (excellent resource for used K-Bike parts BTW) and today was the day to dig in on the diagnostics.

    DIAGNOSTICS:

    First I swapped relays. Not knowing which relay was for up and which was for down I swapped the front relay for the known good one. Screen went up, screen did not go down. I swapped the front relay back and swapped the known good for the rear relay. Same result. So just to make sure, I swapped the two relays that were in there, for again the same result. Test one, all three relays work fine.

    Second, I tested the switch. First I took apart an old switch I had (If you do this a spring will shoot out) and saw that the wiring was bottom wire is hot for windscreen up, middle wire was common, top wire was for windscreen down. It has a neat little "U" shaped pole that when up or down will touch two poles but when resting won't touch either. I got out my handy-dandy 14" length of heavy wire (aka "the ABS reset tool") and touched the two bottom poles on the back of the switch - windscreen went up. I touched the two top poles, nothing.

    POSSIBILITIES:

    Who knows? My only other thought is that in looking at the wiring diagram there is a stop switch that kills the power when the windscreen goes all the way up or all the way down - I am not sure if it is a plunger or a pole switch (or something else) but could I have either stuck it in too far so it caught if a plunger?

    I am officially stuck Anyone have any ideas? My next step involves taking it to Anton and while I do like Anton and love his work I am not sure when I will have the time to do that (and then there is the "I'd rather blow the $$ on a netbook thing )
    Ted
    "A good stick is a good reason"
    1994 K75RT
    Moto Pages

  2. #2
    Dum vivimus vivamus ted's Avatar
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    Oh, and lesson learned the hard way - you don't need to take off the whole windscreen assembly to get at the relays, just turn the bars hard to the right and reach in.
    Ted
    "A good stick is a good reason"
    1994 K75RT
    Moto Pages

  3. #3
    I had problems with such a screen years ago and don't remember much about it at all. But I think that is a two-way motor that runs one way for up and the other for down.

    Go straight to the motor terminals and see if it will operate in both directions. If not - motor problem. If it does then the down command isn't getting there.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  4. #4
    Dum vivimus vivamus ted's Avatar
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    Thanks Paul - I may have to take this to the shop, I had a hard time trying to get that front plate that holds the windscreen out. I only managed to get it about an inch or so out before it hung up on something and I ended up just putting it all back together. Is there a trick to this?

    Something tells me that motor isn't cheap
    Ted
    "A good stick is a good reason"
    1994 K75RT
    Moto Pages

  5. #5
    Registered User robsara's Avatar
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    Quote Originally Posted by Ted View Post

    Something tells me that motor isn't cheap

    Why? Does it say BMW on it?
    Rob R
    1994 K75 My first bike.

  6. #6
    Dum vivimus vivamus ted's Avatar
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    LoL - yes, on closer inspection it does.

    Now the weird stuff (and pictures are needed...)

    I went out to test the switch - the middle pole supplies the power and it shows 11.8v at rest. So, I decided since I could see the relays easily by just moving the handlebar and looking inside the fairing maybe I could also see/access the windscreen motor.

    The Bike.


    Hmmmm - maybe that is the motor back there just behind and to the right of the cluster...


    Yup, that's it. Here is a close up.


    Well now, since I could not find a wiring diagram for a K75RT with electric windscreen I found one for a 1993 K1100LT and since that year shared similar parts I hoped it might match.

    Yup, if you could look as close as I could you would see that is a brown wire, a smaller yellow/black wire, and what looked like a yellow/violet wire behind it.

    So for some odd reason in a flash of confusion I decided to see if there was power across the brown and yellow/black poles when I hit the down switch. I put the red probe on the yellow/black, the black probe on the brown and hit the switch. I didn't notice the reading because the SCREEN WENT DOWN!

    Wahoo, immediate problem solved! Longer term problem still lingers. When I hit the down switch nothing happens. When I put the probes on those two electrical connections, the screen goes down. Something tells me the motor is the problem Would it make sense to guess that there is some failsafe to shut the motor off when it is all the way down that I stuck and when I put the probes on those two terminals it bypasses the stuck shutoff?
    Ted
    "A good stick is a good reason"
    1994 K75RT
    Moto Pages

  7. #7
    Dum vivimus vivamus ted's Avatar
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    PS - for people with LT/RT bikes with electric windscreens...

    See to the left of the cluster there is what looks like a gray box?


    Yup, those are the two relays, easily reachable by moving the handlebars.
    Ted
    "A good stick is a good reason"
    1994 K75RT
    Moto Pages

  8. #8
    rabid reader dbrick's Avatar
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    Quote Originally Posted by Ted View Post
    When I hit the down switch nothing happens. When I put the probes on those two electrical connections, the screen goes down. Something tells me the motor is the problem
    Ted,

    I don't agree that the motor is the problem. How can the screen go down if the motor doesn't run?

    Because the screen goes down, I think the motor works. If the motor works, there's nothing wrong with the motor. I think the problem is an open circuit either in the "down" side of the swtich, or in the "down" side (yellow-black) wiring. I'm thinking the screen went down because you provided a current path through your voltmeter.

    To test my hypothesis, use some scrap wire, and take the stock switch and wiring out of the circuit (so to speak). Run one wire from the motor common to battery +. and then jump from the "up" and "down" motor connections to ground. If the screen goes up and down - and I think it will - the motor's just fine.
    David Brick
    Santa Cruz CA
    2007 R1200R

  9. #9
    Dum vivimus vivamus ted's Avatar
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    Dave - I think you are quite right. I should have said, the switches attached to the motor that stop the motor from going up and down when the screen hits full up or down

    I finally found a correct wiring diagram, it shows those wires as part of the full/stop microswitch: http://www.bmwk.nl/webPaginas/sleute...schRuitK75.pdf
    I also found a post on the K11OG site that explains how they work.

    Looks like as you noted the motor works fine, and when I put the probes on I opened the full/stop microswitch circuit allowing the screen to work.

    Wonder if this is a fixable thing???
    Ted
    "A good stick is a good reason"
    1994 K75RT
    Moto Pages

  10. #10
    rabid reader dbrick's Avatar
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    The K11OG thread is excellent: a clear explanation.

    Of course it's fixable! The hard piece to replace would be the motor if it were duff, and it isn't. The rest is merely wires and switches, and, as you observe, your bike's problem is probably that one of the limit switches has failed, or gotten gunky inside, or something.

    The motor shows as "actuator" in the parts fiche; from the K11OG page, the limit switches are part of the motor; they don't appear separately in the parts diagram. But...microswitches aren't mysterious, and if a switch has really failed - as opposed to a connector failure or a wiring failure - I'd think a bit of poking round would result in finding a substitute. But make sure you look at the limit switch wiring and connectors first - the fault is more likely there.
    David Brick
    Santa Cruz CA
    2007 R1200R

  11. #11
    IBA #44567 Ken F's Avatar
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    Ted, I've been fighting the same thing of Dad's '95 K1100LT. On the drive end of the motor, there is a gear about the size of a quarter that contains your up and down "triggers" (for lack of a better word) for the UP and DOWN limits, which are microswitches. My bet would be that when your switch had stuck in the down position for an extended period, the gear jumped one tooth so that one of the limit switches is not functioning. You will have to take the windshield mecninism off, and pull the motor off the actuating frame to see what is going on, but once you do it will become clear to you. you can run the motor up and down with a battery charger and watch how the micro-switches work. It will be very clear to you what the problem is, as it is a very simple system.

    As was said before, if the motor will run one way, it will run the other, so it's fine.
    You should lube the mechinism while you are in there anyway, which from my reading and working on Dad's is the most common reason for failure. If you want to PM me your email addy, I'll send you several good links on the subject.

    Hope that helps,
    Ken
    IBA #44567 Pres. Springfield BMW Roadriders
    "Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
    -Albert Eienstein

  12. #12
    Quote Originally Posted by 460Jetboat View Post
    If you want to PM me your email addy, I'll send you several good links on the subject.

    Hope that helps,
    Ken
    Why not post the links here where they might be of value to others as well?

    My windshield just stopped working, I will be looking at it soon.

    Thanks for the photos Ted! They will help me get started.
    ride what you've got; enjoy the ride!

    Turbo Fluffy Motoclub - IBA 50182 - BMW MOA 69187

  13. #13
    IBA #44567 Ken F's Avatar
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    Good idea, it didn't even dawn on me.

    It has been 4 or 5 months since I was researching the windshield problem, so as soon as I have time to dig through my bookmarks and find them, I'll put them up along with some pics as ours is still off of the bike, and I think with some pictures I can better explain how it works.

    Ken
    IBA #44567 Pres. Springfield BMW Roadriders
    "Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
    -Albert Eienstein

  14. #14
    IBA #44567 Ken F's Avatar
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    Okay from the archives, here's a pretty good thread about the windshield which shows the gear drive & micro-switches once the motor is removed from the windshield frame:

    http://www.k11og.org/forum/viewtopic...=9090&start=15

    I'll try and get some more up tonight

    KEn
    IBA #44567 Pres. Springfield BMW Roadriders
    "Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
    -Albert Eienstein

  15. #15
    Pevey jpevehouse's Avatar
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    If anyone has links to rehab the actual slider and mechanical parts, could you post it. I've been all over k11.org and found good information there but I'm more of a visual guy. I've had my set up off the bike to clean and lube and it just feels stiff when moving. I've got new relays but I don't want to fry them if the mechanics don't work right.

    Great thread. I'm following everything closely. You are helping lots of people with this, Ted.
    I must go down to the seas again, to the lonely sea and the sky,
    And all I ask is a tall ship and a star to steer her by,


    James and his 1988 K100LT

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