K11 Owners Group

[Ted]

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. Test two, switch excluded.

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
KOG#1

[Mystic Red]

[Ted]

Hmmm - good question. I am pretty sure I did hear something click inside the fairing, but that is a good question. Luckily that switch comes out pretty easy and I have a handy Radio Shack pocket multimeter
_________________
Ted
KOG#1

[garynali]

Gday Ted
Get your meter and check for power coming into the switch ( the same voltage as at the down side hopefully 12 plus) then check for voltage out of the switch when you operate it. Switch eliminated. Next operate switch and check for the same voltage at the relay coil in, if ok check the relay earth by jumping it directly to a known available good earth position. If ok so far check for power from buss to motor by putting the meter on the power in side of the relay should be live with ignition on, if good switch on again and check power out terminal if ok check for power at the motor. Your problem will be in there and in an old bike often at more than one place. Not a lot of resistence is needed to stop 12VDC from doing the job.
Good luck
Gary C
93K1100RS

[Ted]

Thank you Scott, you've indirectly solved my immediate problem, long term still a mystery

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 Drake came to the rescue again and 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
KOG#1

[Ted]

OK, on further examination it looks like those brown and yellow/black wires are for the full/stop microswitch - I found a wiring diagram and a post here by RBM that explains how they work. I think what I did by touching the two was to bypass the (faulty) microswitch
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Ted
KOG#1

[rbm]

Hi Ted,
There are a few copies of that schematic referenced in various forums. The unfortunate issue with the referenced diagram is that it is drawn incorrectly. I discovered this while building a relay card for my electric windshield. I used a JPEG editor to modify the drawing. I'm posting the corrected diagram below. Most of the superfulous circuitry (on the right hand side in the diagram to which you referred) has been eliminated for simplicity and the wiring around the up-down window adjust switch is the part which I corrected:



The limit switches are SPST - NC type. Since they are normally closed, the ground circuit is normally continuous. The microswitches ride against a cam follower that moves with the drive gear. When the cam follower reaches a physical limit (UP or DOWN), the associated microswitch is engaged, breaking the circuit, causing the relay to drop and stopping the motor. If the microswitch is malfunctioning, the contacts probably are opened up and not making a circuit. Two conditions can cause this -- (1) the contacts are burnt and not making or (2) the microswitch actuating arm is mechanically stuck in the engaged position because of dirt, etc.

I think you have isolated the problem to the DOWN limit microswitch within the motor unit. When you bridged the Yellow/Black and Brown contacts with your meter, you provided continuity for current, bypassing the failed switch and engaging the DOWN relay. Thus your screen descended.

The repair may require you to remove the screen assembly from the fairing to get at the motor, to test the microswitches further. Those type of microswitch are easily sourced at an electronics supply so expensive dealer diagnostics and repair is not needed if you feel up to the task of replacing the microswitch.

I should note that once the screen reaches any limit, UP or DPWN, the circuit is broken and pressing the UP/DOWN switch on the dash will not have any detrimental effect on its contacts. In other words, you can't possibly burn out the dash switch in this condition. On the other hand, if the screen is mechanically stuck (guides are not lubricated, for example), it may be possible to burn out switch contacts because the motor will draw excessive current being a reactive load.
_________________
- Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer

[Mystic Red]