Greets everybody.

So I'm in the process of fixing my OEM instrument cluster. It's suffered water damage and has fried a PCB and FFC (flexible flat cable). Additionally, the gear indicator LCD display is cracked but the board it's mounted on seems to be in perfect working condition.

The user-end problems with the instrument cluster are:
1) No gear number indicator.
2) Non-functional speedometer/odometer.
3) No backlighting at all.
4) No "low petrol" light.
5) Clock often goes off and resets itself.

This is what I found when I opened up the cluster:

(larger image)

Pretty awful. Initially, I thought this was the speedometer controller (the PCB). Reading a few threads on here, a couple of people suggested it's actually the tachometer controller with references to Realoem indeed showing it as the tachometer controller. Funnily enough, my tachometer works perfectly fine, yet this board is severely damaged, so I'm still willing to believe it's for the speedometer.

I've probed the contacts around the area and there's lots of completely dead leads from where it's corroded and blown, so I expect certain things not to function.
I've seen the PCB in question to buy on Motorworks, but I'm hoping to salvage it if possible just to save myself £40.

Next up, LCD gear position indicator:

Like I said, the board the LCD display sits on seems to be of perfect working order as it still attempts to display something on the dysfunctional broken LCD display.

Anybody have an old instrument cluster lying around where they can sell me that tiny little LCD display? I was thinking about replacing the LCD display with an LED 7 segment display to make it more interesting. I believe the LCD segments are running on 5VDC, not sure, but if that is the case, I was thinking of wiring it in with resistors on the segments as the LED one runs on 2VDC or something.
I've seen the gear position indicator (with the board) on Motorworks for £30.

As for lights not lighting up, that could be because of the FFC being burnt. All the bulbs actually work as I've tested. The connectors that go into the back of the instrument cluster need some attention so we'll see what happens.

Once I've finished with all of this and put it back together, I'll waterproof the unit good and proper, maybe change the cover completely as there are cracks in the clear viewing plastic on the front.

So, um, if anybody has any low-cost tips or is willing to sell me a couple of small parts that I require, then let me know?

Thanks.
Nitrogen.

I have a used tachometer that I believe has a defective gear indicator board in.
The failure was that the green Neutral light would not illuminate in neutral, but the LCD gear display worked perfectly.
I also have an early speedo unit with a broken drive gear but little if any rust.
The clock in this one actually works too, but the edges around the LCD face of it are edgy & peeling and it looks poor.
I have a blue printed circuit that's in pretty good shape. I believe it's for an early one that had both fuel lights, but probably could be made to work in a later app. with your handy craftsmanship. I do not have a good new style fuel light control board.
Basically, You decide if it might be worth your while to pay the postage from USA to UK to get this stuff.
If you think you want it, I'll put it in a USPS flat rate box & post it off to you. You send me $20 USD + whatever the postage turns out to be.
If you mail me later & tell me that you got NO value out of the deal, I'll send you back your $20, you'll have to eat the postage .
I'm sorry I don't have a spare glass.
Once you get it all up & working, you might do your best to seal it up from water, but try to fashion some Gortex vents in the back like newer ones so it can breath out.
Let me know. Sounds like a bargain to me if you aren't in a hurry.
Regards, ibj.....

Hi ibjman.

Thanks for your response, and I am definitely interested. I have a few questions however:

Referring to "both fuel lights," you mean like this?

Because that is what mine is, but I have only ever seen the right light illuminate (going back months ago), I never knew what the left light was for, haha.
I'll have the printed flexible flat cable from you if it's all working!

What do you mean by "early speedo unit with a broken drive gear"?
I'm looking to replace this particular part, is this what you mean?


My gear indicator board works fine, but as long as the actual LCD display is fine in yours then I can just swap them over like so:

(showing the back-side of the LCD display where it meets the board)

My clock LCD and clock board are fine, I think it's just the contacts on the back of the instrument cluster being dodgy or something, hooking it up to a 12VDC bench supply shows it working perfectly.

But yeah, if this is all positive for you then I'll definitely take it if the postage isn't ridiculously high and hoping that all the parts work well then the postage won't even matter much because it is worth it.

Thanks again for your reply.
Nitrogen.

The cost to UK for a medium Flat Rate Box is $60 US. Since I'm only asking for $20 for me, this might be worth while. I'm not doing this because I can make a profit, I'm doing it because I wish to establish a great reputation of being helpful to my friends (You) at the K100 Forum.
That said, I have just finished a repair on a complete speedo, but I have yet to test it. It will be a couple of more days.
I can't send these parts till I'm sure I'm OK on mine.
Here's some pics of what I probably have for you. The printed circuit blue foil is permanently attached to it's support board. It has a break in the plastic that I think you can repair with a plastic fix kit (or I could if I had time). once it's glued/patched the circuit should work fine. Because that foil board is so large, it and the needed padding require the $60 box. I could not get it in to the smaller, cheaper box.




The next foto is the good Gear indicator LCD, I can definitely part with it and the blue foil board above.

Here's the (I THINK) Tachometer control board that you asked for.
#1 I think I have it's function correctly identified, I have to be sure I might not still need it. Hence the delay.

This next one is the 1985 (early K bike) Fuel warning light control board that contols both the amber and red lights at the lower left of the instrument. I believe it works as "designed".....Meaning, these never worked in a dependable manor. There is a BMW bulletin to upgrade it to a single 7L light. You can read about that elsewhere in the forum.

The last pic shows all the boards I have. The one labled Gearshift control board is the one I think may be defective causing the green N light not to work. It is the one I removed from MY speedo. As I said, I have to test it.
It seems there is some doubt about which board actually controls that green light circuit. Hence I have to test before I can mail.
On my speedo, I changed that larger Gear control board. If that does not fix the neutral light I'll have to try the little board that you're wanting.
I'll know in 3 days

Hi Ibj.

The PCB far right is the speedometer preamplifier...

If the "green light circuit" is the neutral light......and you achieve 0 at the lcd display
but not the green indicator light...the reason probably is a blown output transistor.

About the broken plastic tab, this could have been done on purpose........
Have a look at this service bulletin.
It been different fix on these speedo contacts during the years, this wasn't the final one.
About a couple of years later two small screws was used to keep the contacts in place.

About the fuel level PCB (which did use the thermistor sensor) revision, it was the 7L
warning lamp that was leaved out.

ibjman, and you're very generous at that, I wouldn't mind giving you some extra for yourself.

The break in the plastic should be an easy fix, it /isn't/ in a obscure place that may be difficult to fix, and as Inge said, it may have been done on purpose even if it is a coincidence, at least I know I shouldn't have any intermittent problems going over bumps if ever (as the service bulletin mentions); so I'm fine with that.

When I said my left fuel light had never been illuminated, that's because that bulb was blown I found out, heh.

I'm most interested. You have all the parts I require. Let me know when you're ready to part with them, and what bits you're keeping; there's no rush.

Nitrogen.

Greetings Gentlemen, While on the subject of the cluster when I looked into my tech which would only go to 3K rpm I found a small spring lodged against the needle stopping it from moving. This might have been dislodged from somewhere when my neighbor dropped my bike down onto the right hand side. Could anyone tell me where that is supposed to hook to? Have searched but not found a pic that shows it

Since this got bumped, I will announce that my instrument cluster works now!

Got nice LED back lights, gear indicator display works, speedometer works and is properly calibrated using Karamba.

A quick word about Karamba, testing the speedometer with it was rather dodgy. The instrument only allowed certain frequencies (from the program) to pass and display the speed. It worked best around 30 MPH so that's what I set it to. It also didn't revolve the odometer gears very well and I thought I would have a problem with that.

However, upon putting it all together and putting it back on the bike, it worked without a fault, and I believe the signal from the speedo sensor on the bike is not a pure sine wave like Karamba produces.

I've read documents online (non-official, just some guy's diagrams of the K100 sensors) that it looks something like this:

Maybe the developer of Karamba should look into that.

My trip-meter reset knob also arrived from MotoBins, so I'll find another time to add that. I've already rolled the trip-meter over since I've fixed it (only holds 3 digits).

All of this wouldn't have been possible without the help of ibjman and his generosity sending me the parts. You're a hero, man! Thanks a lot.



Nitrogen.

Ok I jealous. Love the blue lights...But right now I'd settle for any color lights! Hope to have mine back on this weekend. Ya'll got some nice machine over across the pond. Good work.

That little spring may well have been from the reset knob of the odo. The spring I refer to is about 1/4in long and about same dia and has 3-4 turns.

The reset knob is located to the left side of the cluster, so I imagine if the bike dropped on its right side, it could've fallen into the spring of the needle.

My original reset knob was made of plastic and broke very easily and the spring became free inside the cluster. Very possible.

Thanks men, that must be the spring from the reset knob which was missing when I bought the bike and the spring must have been inside all along. Good deal. I'll be able to put my cluster back together and mount it tomorrow. Finished relocating my FPR today along with a few other thing that had to go back on the bike. Hope to have time tomorrow to remount the fairing and trim pieces. Gotta have her ready to leave out of here on the 24th to go see my grand kids. Thanks again, ya'll are great!!

BTW what happens when you click on "DRAFT" , where does it go? I can find it!

Before you finally reassemble don't forget to treat all connections with DeoxIT and to seal up all the water ingress points.
Regards,
K-BIKE

Woo Whoo, Took the gal for a test run and the speedo is working so far to within 2-3 mph, tech is working fine, got oil light, high beam indicator, only left cluster light working and lost my bulb check light which was working before I took the cluster apart. after my trip I'll take it back down and try again. Anyone have any advice feel free.

All your lights should be working ideally. Since it's not a quick process, when you open it up, just put a multimeter across the bulb holders (they have metal plates on either side which are good for this). You can set the multimeter to check resistance via Ohms setting, "1" means no current passing, anything to change this value close to zero indicates there's a connection, thus the bulb should be fine. Check all the bulbs are securely in place (almost all are those wedge bulbs, you can get badly made ones that you have to wiggle around to get contact). There's not much else to suggest, except to make sure the cables are in place at the behind of the cluster. Any blown bulbs can be replaced and they're not hard to find at all. The green coloured covers over the bulbs can be taken off and put on any newer bulb.

Thanks Nitrogen, I'll check it out with a meter. I did change all the bulbs when I had it opened but didn't do the meter check.