Speedo broken, how to repair>???

[R1ckM]

I have a 89 325i vert, the speedometer (mph/km not the odometer) doesn't work. Sometimes it will jump up to speed but only for a few seconds. I removed my gauge cluster today, just wanted to know where to go from here???
I will be replacing my odometer cogs/gears as well.

So do I need to open up the cluster to fix the speedo issue or is it from the actual sensor, where would that be located exactly?

Thanks for any help.

[dogsbark26]

I think it is much more likely the speedometer and not the sending unit located on the differential.
While some claim success re-flowing the solder in each connection on the speedometer circuit board, I just swapped in a working speedometer.
Yes, you will need to remove the cluster (easy job made easier if you first remove steering wheel) and disassemble the cluster to re-flow solder OR switch speedometers.

[R1ckM]

I am handy with the soldering iron (pc repairs). I got the cluster out in under 10 mins, left the steering wheel on. It was in the way a little but with some delicate angling of the cluster, it slid right out. I will take it apart today then ^^
I just didn't want to spend $20 on those gragistic gears and then need to replace the whole cluster or something you know...

Btw anyone vouch for the gragistic odo gears?

[dogsbark26]

Be careful not to bend the six or so wire pins on the back of the speedo when re-inserting it into the main cluster board.
I have no personal experience with the garagistic gears.

[Northern]

This sounds exactly like the speedo issue I've had with every e30 I own.

Check the connector for the speed sensor at the diff.

[R1ckM]

Took it out, then apart. I did notice the little pins in a few areas and the plastic connector you have to pop off to get the speedo/odo out. Its a Motometer btw
Heres what i found...





The odo gears look newer so, they must have gotten replaced before. I don't see the need to do it again, as they are in good cond.

The speedo, I can't find and "brass" bolts to tighten on the back. I noticed the board is a little dirty/corroded in the area of the upclose. Not sure if it will affect the functionality of the speedo though.
I just put it all back together.
What now?

[dogsbark26]

Yeah, those dirty/corroded areas on the board do not portend a bright future for that speedometer. I would replace it. You might contact Gregs///M on this board if you want someone to try to repair it. I do not recommend North Hollywood Speedometer.

The intermittent operation of the speedometer you described in your first post is indicative of a broken solder flow on one of the connections to the speedometer circuit board. What I was saying is some people have had success re-flowing the solder on each of those connections.

The brass bolts are on the rear of the fuel gauge and the temp gauge. The both hold those gauges to the main cluster board and provide electric ground for those gauges. Ensure they are snug and clean.

Northern is right.

Check the connector for the speed sensor at the diff.

That connector (on the rear differential) is subject to the elements.

[e30topdown]

I took sandpaper to all pins/connectors and then hit them with dielectric grease before reassembly, too. That and reflowing the solder really made a noticeable difference, although now periodically, it will "spike" about 15 mph and immediately go back to normal. But now it is rock-steady instead of bouncing all over the place or dead, where I had to whack the front of the cluster to get it to work again. GL

[e30topdown]

And those gears have been replaced. They look newish, and not colored different bits like OE. Mine were colored goo, actually. I used odogears back in 2006, when I got the car. Odo had gone out three months before I got the car. The guy I ordered from was a big help, I remember, during installation.

[Gregs///M]

Don't rule out fuses and the speedo sensor connector. Since the sensor connector is located in the rear, it is exposed to the elements more than anything inside the car. Remove the connector at the rear differential and clean the contacts. Also tighten them up so they grasp onto the speed sensor tighter. This connector is well known to develop oxidation and become loose over time. Definitely check it.

Also the fuses, over time, can develop micro cracks which can expand with temp and current load. This will give you an intermittent operation of the cluster and its functions. Replace the cheap 7.5A fuses, #10,12, and 21.

If those don't help, I would reflow the speedometer and cluster main board.

Of course, after that, you'll need to inspect the car wiring for damage. Lastly, you can try swapping the speedometer assembly.

Other troubleshooting techniques would be to verify a pulsed signal at the brown/red wire in the white connector. It will have a pulsed signal that increases with vehicle speed.

GL

[R1ckM]

Put the modometer back in, didn't work. Took the speed sensor off the rear end and cleaned the area, pluged it back in.
Speedometer now working, thanks all.

[dogsbark26]

Woo hoo! Glad to hear Gregs///M's simple solution fixed yer problem.

[///M42 sport]

I have the same issue, will try cleaning the sensor on the diff. now too thanks.

[///M42 sport]

so I went to check out the sensor on the diff...then the wire broke right where the female plug is so I cant really splice it without getting a new female plug. Damn,,,part number anyone?

[KHTRNAK]

Amazingly useful post!!!