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1Back to top Go down    Speedometer not working on Tue Oct 30, 2018 11:56 am

gabriel


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Hi

My 1984 k100 instrument cluster is not working.
Tachometer is fine.
Speedometer stopped working approx five years ago.
Final drive sensor is fine.
Opened the instrum3nt cluster yesterday @nd the internals are in excellent condition.
Any suggestions?I am at my wits end trying to fix this problem.
How do I test the instum3nt cluster?
Thanks
Regards 
Gabriel.


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;BMW; 1984 BMW k100..frame number 6228?
    

2Back to top Go down    Re: Speedometer not working on Tue Oct 30, 2018 2:43 pm

robmack

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Use Karamba to bench test the cluster.  You're limited in diagnosis options unless you have access to an oscilloscope.  You can try to disassemble the instrument cluster and clean contacts inside the box, that sometimes helps to cure the problem.

The electronics in the instrument cluster are fairly robust so it's unlikely to be a circuit failure. It's morelikely to be a mechanical failure with the servo motor in the speedo.  See my page on OEM schematics for an idea of how this piece works on your bike; it might lead you to a solution.


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Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

3Back to top Go down    Speedo not working on Tue Oct 30, 2018 4:03 pm

smoll1


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I had the same problem and fixed it last weekend.

My sensor was good. Wiring to instruments was good.

I had checked inside the instrument numerous times and all seem good.

In the end I cleaned all contacts carefully and the 3 pins in the back of the Speedo I twisted about 20 degrees as others said this worked. I also put tiny amount copper grease on contacts. 

Put all back together and it been working fine even in the cold weather.

I also.put bit sticky foam on the insturment back cover to keep the pins in the contacts better.

Hope this helps. I was worried it was still not going to work but it is spot on. Very Happy

    

4Back to top Go down    Re: Speedometer not working on Sat Nov 03, 2018 6:25 pm

gabriel


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Hi

Just wanted to post an update.
Completed a few more checks and confirmed the following..
-rear wheel sensor is fine.
-checked continuity between sensor and speedometer plug. Multimeter beeps at pins 22 and 23 on the speedometer plug.
-checked all connections inside the speedometer. Pins all have a solid connection. The three pin connector at the top right of the speedometer was checked. I used deoxit...no change......
I decided to use solder to plate the pins and hopefully ensure a solid connection.
Strange thing happened when I removed the three screws on the speedometer face to get to the circuit board. The resting position of the needle moved. The odometer wheels look fine. I rotated them by hand and they seem to be ok.
When I checked the circuit board I noticed someone had tied wire around two outer connectors most likely to ensure a solid connection ?
I’m thinking, perhaps it’s the stepper? Motor that is faulty. I don’t understand how there could be a fault with the circuits.
I am at my wits end trying to resolve this issues.
Anything else I can do to check the speedometer.

Regards

Gabriel


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;BMW; 1984 BMW k100..frame number 6228?
    

5Back to top Go down    Re: Speedometer not working on Sat Nov 03, 2018 8:46 pm

RicK G

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Check the face plate if it is buckled then it can stop the needle working and you say it seemed fine when the plate was removed. They're like vampires, sitting in the sun isn't very good for them.



Last edited by RicK G on Sat Nov 03, 2018 11:13 pm; edited 1 time in total


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"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats."  from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

6Back to top Go down    Re: Speedometer not working on Sat Nov 03, 2018 10:13 pm

gabriel


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Hi
Face plate and all internals are in excellent condition.
Deoxit seemed to be a waste of my money.
Perhaps a good quality electrical contact cleaner/spray would have been more effective..
Oh well.
The speedometer needle moves freely and slowly returns to the zero position.there is no binding.

Regards

Gabriel


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;BMW; 1984 BMW k100..frame number 6228?
    

7Back to top Go down    Re: Speedometer not working on Sun Nov 04, 2018 9:52 pm

gabriel


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Gold member
Hi 

I have a question regarding the instrument cluster. 
Are there any other circuit boards besides the one underneath the speedometer which I should check?

Thanks

Gabriel


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;BMW; 1984 BMW k100..frame number 6228?
    

8Back to top Go down    Re: Speedometer not working on Sun Nov 04, 2018 10:04 pm

robmack

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@gabriel wrote:Hi 

I have a question regarding the instrument cluster. 
Are there any other circuit boards besides the one underneath the speedometer which I should check?

Thanks

Gabriel
Yes, back in post #2, I provided a link to the page with some OEM schematics. There are two boards associated with the speedometer/odometer. One is a long think board that conditions the signal from the speed sensor in the final drive. The other is a servo driver board. If you are certain that the conditioning circuit is operating, then you need to check the servo driver. A picture of that card is on the page I linked.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

9Back to top Go down    Re: Speedometer not working on Sun Nov 04, 2018 11:04 pm

gabriel


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Gold member
Hi
I am certain the issue with my speedometer is electrical. All the connections seem to be secure.
How do I test the two circuit boards?
The tachometer is working. I checked the speedometer internals.
The odometer wheels are fine.
There is a circuit board under the tachometer which includes approx six connectors. There are three? Transistors in the top right corner of the circuit board.
How relevant is that circuit board to the proper functioning of the speedometer.

Thanks

Gabriel


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;BMW; 1984 BMW k100..frame number 6228?
    

10Back to top Go down    Re: Speedometer not working on Sun Nov 04, 2018 11:39 pm

charlie99

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Gabriel   you may have to lift the rubber protection layer that fits around the pins of the electrical connector 26 pin thing

under that you may find the membrane circuit , inspect it closely

I had one recently that someone had shorted out the globe circuits  causing the membrane to burn out somewhat , especially on the negative - ground common sections

I had to join burnt out sections with wire links to the good sections and in some cases directly from the pins  to areas that were showing open circuit

perhaps lift the backing rubber and post a pic for us ?

the other thing you could probably do is chase each of the wires from the appropriate pins , 1> to the 4 pin connector strip on the pickup amplifier
then to the 3 pin connector to the servo motor board

there have been documented mods to these connectors , and the wiring from pins on the input to the speedo drive stuff


ill include a pic of what I found after I lifted the rubber  ...below , lets hope yours is not so bad






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11Back to top Go down    Re: Speedometer not working on Mon Nov 05, 2018 1:45 am

gabriel


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Thanks. 
I will go with your suggestion.
I used a multimeter and checked for continuity between the three pins in the top right corner to the speedometer central pins. All good.
I will post an update.

Regards
Gabriel


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;BMW; 1984 BMW k100..frame number 6228?
    

12Back to top Go down    Re: Speedometer not working on Mon Nov 05, 2018 6:13 pm

BooG

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My speedo was knackered a while ago. The soldering iron trick worked, and it turned out to be the sensor in the final drive. Replaced it with a second hand one from Motorworks....solved! May be worth a shot, even though the current troubleshooting may lead you to think the sensor is OK.

    

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