Speedo woes

[billday]

I've been struggling with a flaky speedometer for way too long, but in the last few days I've made major progress diagnosing my troubles.

Using Karamba, and a second (mostly trashed & useless) instrument box I had lying around, I've established that I have two speedometers that work, but not when they're installed in my "good" box. So, the problem is that the signal is not getting to the speedometer.

I've cleaned up (De-Oxit) the three pins that plug into the back of the speedo, no change. Could the grotty looking wires in the blue tape leading to the three pins (see pic) be the problem? Anybody have any suggestions?

Thanks,

Bill

[The Mighty Gryphon]

Do you have a ohm meter or a continuity tester?  I would start by checking the continuity from the sender in the final drive all the way to the speedometer input.  It sounds like you may have a bad connection from a wire to a contact in a connector or from a terminal on the flexible printed circuit to the trace. 

Checking the continuity should show you where you are losing the signal.

good luck.

[Inge K.]

Could the grotty looking wires in the blue tape leading to the three pins (see pic) be the problem?

It could be a reason to the problem....check that the copper path in the conductive film is unbroken.

But what also is important is that the melted plastic indicates that a speedometer with a internal short have
been installed....as a lot more current than normal have been drawn through this copper path.

Check that you don't create more shorts as now a lot of this copper path have no isolation and it's 12V+.

[billday]

Hey Gryph, hi Inge,

I've tried checking the continuity from the sensor up to the terminal/plugs at the front of the bike, and inside the box from the pins on the back of the box to the three pins that go into the back of the speedo unit. Current goes all the way through but I have to admit that I'm not a very sophisticated user of the instrument.

Inge, I see what you mean. But no idea how to remedy the problem. Seriously ready to go aftermarket.

Bill

[Inge K.]

Inge, I see what you mean. But no idea how to remedy the problem. Seriously ready to go aftermarket.

What I did have in mind is if this melted insulation have happen when you have owned the bike and tested
different speedos......you know which one that have caused this.......and avoid using it / have it checked
as it obviously have a short.
Next is the conductive film w/o insulation just check that the uninsulated part don't come close to any metal
inside the cluster, add tape as needed.....or change the conductive film.

About the nonfunctional speedos, as they do function in your spare cluster.......I would guess that you
have a nonfunctional signal preamplifier.
Try to swap it with the one in you spare cluster.....it's the pcb where you can see a raw of resistors
down left corner in your picture.

[billday]

Could the grotty looking wires in the blue tape leading to the three pins (see pic) be the problem?

It could be a reason to the problem....check that the copper path in the conductive film is unbroken.

But what also is important is that the melted plastic indicates that a speedometer with a internal short have
been installed....as a lot more current than normal have been drawn through this copper path.

Check that you don't create more shorts as now a lot of this copper path have no isolation and it's 12V+.

Hey Inge,

I'm thinking about soldering in jumper wires to bypass the path in the blue tape. Is that insane?

Thanks in advance,

Bill

[koapono]

I have soldered in jumper wires to repair instrument cluster. first thing to do is make certain you have no shorts as the jumper will likely carry more current (read heat) and further make a mess of things. I bought some insulated small gauge wire from radio shack, the kind used by folks who wrap their own coils, armatures or similar components, ends must be cleaned and free of the varnish/color coating prior to soldering. I soldered ends and secured wire to blue ribbon with a drop of glue spaced at intervals along its length. be sure glue you use doesn't react with and melt the blue ribbon. I've no pics but repair is straight forward and has lasted for years without a problem.
g'luck