Speedo needle

[frodef]

I'm doing a project to replace the broken clock in my K75 with a generic one from ebay/china (something like this).



While working on this I think I touched the speedometer needle, and now I think it's falling down below where it used to, and when driving it indicates some 10-20 km/h below actual speed. Does anyone know the procedure to position the needle correctly?

[wmax351]

It should stop at the position that would be 0. When you use a soldering iron near the pickup, the speed should be about 75 kph (assuming 60 hz. Not sure what Norway is).

[WayneDW]

Perhaps I'm miss-reading your problem but you should be able to pull the needle straight off, reposition it, then push it back on.   That's how I fixed the always reading 10MPH fast problem.  I pulled the needle, lowered it to read "-10" at idle.

[frodef]

Perhaps I'm miss-reading your problem but you should be able to pull the needle straight off, reposition it, then push it back on.   That's how I fixed the always reading 10MPH fast problem.  I pulled the needle, lowered it to read "-10" at idle.

Ok, thanks. Btw the typical resting position for the needle seems to be slightly below the (unlabeled) "10 km/h" mark, it seems from an image search...?

[frodef]

Clumsy me managed to break the speedo "axle" needle trying to reseat it  :dunno  I patched it all together with a piece of an (actual) pin needle, my smallest size heat shrink tubing (that I never thought I'd find use for) and some superglue. That seems to work ok, but there's still some bad electrical connection somewhere that makes the speedo only work occationally. On a trip saturday it would work reliably below 80 km/h, but whenever I hit that speed the needle would instantly fall down to zero. Guess I'll have to find some way to measure the output from the sensor and/or generate a known-good input signal. Sigh.

[Inge K.]

Guess I'll have to find some way to measure the output from the sensor and/or generate a known-good input signal. Sigh.

Have a look at this thread.

Mvh. Inge K.

[frodef]

Have a look at this thread.

How on earth have I missed that!? Looks perfect. Thanks Inge.

[frodef]

So I did two things: First I took out the speedo sensor, wiped it off and put it back in. Then, the speedo worked rock solid... for 500 meters or so. But that should indicate a sensor problem. Then I did the Karamba thing, with no response at all from the speedo. Which should indicate the problem is in the speedometer itself. Sigh. Guess I'll try to bench-test the speedometer next.  :musicboohoo:

[Inge K.]

Another known problem source in this circuit is the connectors between the preamp and the speedo pcb.

[frodef]

Guess I'll try to bench-test the speedometer next.  :musicboohoo:

That did the trick it seems. I splattered some "wire glue" at the connector Inge indicated and the simliar one below it (and removed some excessive wire glue from before...) and got Karamba to excite the speedo like never before. So now I just had my first ride with a stable speedo needle and odometer for quite some time  :2thumbup: And the new clock is working well also. Now only the gear indicator is missing, the last piece of this frankenspeedo puzzle. Thanks for all help.

[frodef]

That did the trick it seems.

...though not quite. After a few hours in the garage, the needle was dead once again when I started up, only to come alive again after a couple of kilometers. Quite annoying.

[Inge K.]

The connectors at the preamp doesn't usually make problems, but it won't hurt to check them.
Move the contacts up and down a few times, or even better use some contact cleaner.

[frodef]

That did the trick it seems.

...though not quite. After a few hours in the garage, the needle was dead once again when I started up, only to come alive again after a couple of kilometers. Quite annoying.

After one more day or so, the speedo seems to work well. I think the wire glue needs a couple of days to set before it conducts properly.

[frodef]

The speedometer has been quite reliable for a few weeks now. This is the wire glue I used, it seems to work well for the job, assuming a bit of patience.