What makes e30 speedometers fail?

[E30 Greece]

Speedo problem....please help!!!

Hello from Paros island Greece

My E30 M40 M52b25 has speedo problemand with speedo of cource the economymeter and the distance meter since both get from speedo
I doesnt work or show less than real
BUT when i full the tank and for 10-20km it works fine and shows real speed...also ecometer and distance work fine after tank full....but after 10-20 dead again.
Any help???

[izard2000]

Replacing E30 Speedometer head

Hello everyone, I am currently seeking to replace the speedometer head only from my 1985 325e. I have found one from a 1989 325i and I was wondering if it would still be compatible despite coming from a newer model E30? Does anyone know if using a newer model speedometer head on an older model works??

[superj]

it won't fit yours. you have the older style board and the pins for the speedo are different

[E30_Driver]

Hello everybody. I hope you are well in this complicated period.
While restoring my 1983 e30 there is a problem that seems impossible to solve: the speedometer (and odo) does not work. I state that the rest of the cluster works perfectly (even the lights of the board), the tachometer etc.

From home, I carried out a bench test. I manually wired the connectors of the C2 (white) to see if I could trigger the speedo. With a wave generator I sent the signal to the pin 12, I wired the pin 8 and everything else, following the BMW manual. Result: the tachometer works perfectly! I then disconnected all the cables except the + 12v on pin 13, the signal at the pin 12 and -5v on the pin 8. Even in this case the tachometer works perfectly.

Now, the problem is that when i mount the cluster on the car, it still dosnt work. I checked the fuses, checked the voltages on all the pins and also the grounds and I also replaced the differential sensor and checked that the signal reaches the pins from the wires on the diff. Again no solution!! Dead!!

I then took the pin 12 (where runs the signal) and the pin 8 (negative -5v) and I connected it from outside to the signal generator. Again, nothing. The only try I will do tomorrow is to try to connect from the external even the pin 13..... Anyway, are there ghosts on my car or did I miss some steps?

Thank you so much to those who will answer

[tomstin]

You may want to reach out to these folks. http://www.bavrest.com/index.html

[jbontke]

For anyone interested, my 86 325e VDO tach was not responsive. I tested it in a motometer cluster that worked, so I knew the issue was related to the odometer. None of the solder joints looked cracked. I also noticed that the odometer board can wiggle slightly when removed. When the odometer is installed, it tightens down but I bet hard bumps may cause it to move, thus stressing the solder joints. I went over all the solder joints on the board and the odometer came back to life. Give it this a shot before you throw it out.