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.

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.

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.

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

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.

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

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

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.

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

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

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

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.