new speed sensor. still not working

[peytonracer4]

i installed a new speed sensor because the speedo, odo, and mpg all arent working.
all other gauges are however.
so after installing the speed sensor it still didn't work. i went back, looked at the wiring and the leads broke off to my touch. so i wired in new leads (not original) and everything should be straight.
still doesn't work! i swapped the leads back and forth and neither way works. i can't figure this out. i don't see any other wiring fault. behind the dash looks good and after i redid the leads the wiring under the car looks good too

what should i do?

[e30rapidic]

this for an e30?

do you have another speedo that you could swap in? it could be a bad ground or a circuit may be fried. Sounds like something on the cluster end rather than diff end to me. Do your SI lights work?

http://www.unofficialbmw.com/speedo/speedo_d.html

http://www.unofficialbmw.com/speedo/speedo.htm

[peytonracer4]

Yeah all si lights work.
Why would 2 gauges be out because of a solder on the speedo? The mpg gauss is on the tach.
That's what leads me to believe it's not the dash. But idk

[peytonracer4]

Bump

[Ferdinand]

Why would 2 gauges be out because of a solder on the speedo? The mpg gauge is on the tach.

Those gauges both rely on a speed reading from the speedo sensor in the diff.

Be methodical in analysing the problem. Do you have a multimeter to measure resistance and voltage? If not, buy one. It makes tracing electrical problems MUCH simpler.

Download the wiring diagrams for your car from this link: http://shark.armchair.mb.ca/~dave/BMW/e30/

Study page: "6210-0 INSTRUMENT CLUSTER".

First test whether the speedo sensor is working. Jack up the rear wheels, unplug the sensor, measure resistance across the terminals of the sensor while slowly turning the rear wheels. The sensor is basically just a switch that opens and closes. You should see resistance alternate between zero and infinite as the diff is turning. If that works, plug the wiring connectors back on to the sensor and move up to the instrument cluster.

Look at your wiring diagram. The two wires from the diff-mounted speedo sensor come directly via a Brown/Red (BR/RD) wire to Pin-12 and a Brown (BR) wire to Pin-8, both on the C2 connector. That's the WHITE 26-pin connector on the back of your instrument cluster.

Carefully unclip and unplug that C2 connector, then measure the resistance across those two pins while again slowly turning the rear wheels. Unless your multimeter probes are thin enough, you may need to stick a paper clip into each pin connector. You should see the same thing, resistance switching from zero to infinite as the switch in the speedo sensor opens and closes. If not, then you know you have an issue with the wires running from the sensor to here.

If that works properly, then check for power and ground. The wiring diagram shows that power comes to the speedometer whenever the ignition switch is in the Accessory, Run, or Start position, via Fuse-12, flowing on a Violet (VI) coloured wire to Pin-13 of that same C2 connector. Use your mulitimeter on the DC-voltage setting to confirm there is 12v showing on that pin when the ignition switch is on. If not, then check Fuse-12.

Now check the resistance between any good ground and the ground-pin, which is the Pin-16 Brown (BR) wire on the C2 connector. You should have zero resistance.

If all those simple to check things prove okay on the C2 connector wiring - good 12v, good ground, good signal from the speedo sensor - and your speedometer is still not working, then you know for sure the issue is internal to the instrument cluster.

If that is the case, then jump directly to this thread and follow the links from there. http://www.r3vlimited.com/board/showthread.php?t=220619

Good luck, and let us know what you find.

[peytonracer4]

In reference to that last link, someone mentioned the 2 brass nuts on the back being grounds? I do not have the brass nut on the speedo/gas gauge side.
Before I go testing resistance all around the car could this maybe be the problem? Or is likely to be?
Just FYI the gas gauge does work.

[Ferdinand]

Those two brass nuts clamp the fuel gauge and temp gauge firmly to the printed circuit board inside the instrument cluster, providing the ground contact to either of those gauges.

What's holding the fuel gauge in place if the nut is missing?

If either of those gauges are only working intermittently, then the brass nuts are a good thing to check. Otherwise they should have nothing to do with the speedo or fuel economy gauge.

[Ferdinand]

I'm just curious if you've figured this out yet?

[cappa240]

Ferdinand,

This thread helped me tremendously. Thanks!