What makes e30 speedometers fail?

[Quinthirty]

My speedometer stopped working. Its practically new. I removed the cluster and changed the bulbs and look at the gears as the odometer wasn't running (but speedo was). Now, the speedo doesn't run completely. I think I killed it when I tried to pull the speedo out because when I put it back, the speedometer wasn't working anymore. What to do?

How do I know if I killed the speedo itself? What do I test?
How do I test if there are broken circuits or loose connections?

[Gregs///M]

Replace fuse 10, 12, and 21. Double check the connector at the rear differential. Make sure the connectors are clean and secure. Also make sure the wires are not broken.

[Gregs///M]

Speedometers are also well known to have poor soldering that can fail over time. Example...

[nando]

yeah, the PCBs inside these things are pretty damn awful. I guess BMW had to cut costs somewhere..

[FLYNAVY]

Re-hack of this thread. I've had a similar issue in my e30 M3. It is mainly the speedo, with the same symptoms everyone else has described. It also occasionally affects the engine coolant temp gauge, though that is not very common and tapping it fixes the problem immediately, unlike the speedo where that generally no longer works. Thoughts?

[Gregs///M]

Speedometer is a completely different circuit to your temp gauge. VDO are the only manufacturer of M3 clusters, which commonly fail due to solder joint cracks and cracked electrical traces.

Having the speedometer refurbished by us is the only way to get reliable performance without buying a new speedometer from BMW. We reflow the entire circuit board unlike most other cluster builders. We also replace components such as capacitors and transistors, test the unit and provide 3 year warranty.

[FLYNAVY]

Speedometer is a completely different circuit to your temp gauge. VDO are the only manufacturer of M3 clusters, which commonly fail due to solder joint cracks and cracked electrical traces.

Having the speedometer refurbished by us is the only way to get reliable performance without buying a new speedometer from BMW. We reflow the entire circuit board unlike most other cluster builders. We also replace components such as capacitors and transistors, test the unit and provide 3 year warranty.

Oh awesome……I was worried I would have to replace it altogether. Bookmarked your page for reference after I get back from my current work trip. Thanks!

[long tall eta]

My speedo works when the heats cranked up or very hot out but when it doesn't, the econo gauge, odometer, and the mpg/average mph don't either. As soon as the speedo works, everything else does too

[1843lamp]

My 87 cluster has the same strange issues long tall has just described .The biggest issues I have had with my 87 for 16 years have predominantly been electrical ,but I have only invested about $1000 in work and parts since purchased ,so I consider myself very fortunate even if I have had to live with these electrical problems .

[scipio84]

Hi. I have similar problems with my speedometer.
When I start the car, running cold, it flickers for some kilometers and indicates a speed slightly lower than the real; in the same time, the econometer and odometer don't work (econometer goes to 0 in the moment I release the clutch pedal, and immediately goes and remains to the maximum).
Then, suddenly, these three gauges start working perfectly. They have this behaviour always together.
Other instruments work fine.
If I'm not wrong, both receive the signal from the sensor in the differential; the econometer receives as well the signal of butterfly opening.
When I bought the car, the speedometer was always flickering and it took more than 500 km to begin working fine. Now the running is variable, can be 1, 5 or 10 km.
I was thinking that the oil, when heats up, removes residuals and cleans the sensor, leaving again residuals when I stop the car. But when checked the oil, it was golden yellow, like new. So now I don't understand how the temperature can have any impact.
I want now to remove the sensor and clean it up. I see it's fixed with two small screws; can I unscrew them without any fear? will the oil drop out?

Is there any test I can make on the sensor or on the wiring harness of the connector?

[PKile]

A previous post mentions the vehicle speed sensor signal comes in through the brown/red wire in the white connector. What about the 3 pins on the green connector? I thought those handled vehicle speed sensor data, one of them used to output data to the cruise control system.

[scipio84]

Hi. I have similar problems with my speedometer.
When I start the car, running cold, it flickers for some kilometers and indicates a speed slightly lower than the real; in the same time, the econometer and odometer don't work (econometer goes to 0 in the moment I release the clutch pedal, and immediately goes and remains to the maximum).
Then, suddenly, these three gauges start working perfectly. They have this behaviour always together.
Other instruments work fine.
If I'm not wrong, both receive the signal from the sensor in the differential; the econometer receives as well the signal of butterfly opening.
When I bought the car, the speedometer was always flickering and it took more than 500 km to begin working fine. Now the running is variable, can be 1, 5 or 10 km.
I was thinking that the oil, when heats up, removes residuals and cleans the sensor, leaving again residuals when I stop the car. But when checked the oil, it was golden yellow, like new. So now I don't understand how the temperature can have any impact.
I want now to remove the sensor and clean it up. I see it's fixed with two small screws; can I unscrew them without any fear? will the oil drop out?

Is there any test I can make on the sensor or on the wiring harness of the connector?

Guys, no ideas? no suggestions?

[Gregs///M]

Guys, no ideas? no suggestions?

Without your entire cluster being refurbished, the cause of your problems could be copper oxidation, solder joint and trace cracks, failed Si board, bad sending units, bad wiring. It can be some or all of these issues. If your cluster is not refurbished, consider it inaccurate and unreliable.

[Fabe]

My speedometer is working but odometer meter is not working..

Yes, I have checked that the gears are working. manually spinning the first gear and it spins all the gears and turns the odometer. but when installed back to the cluster. the odometer doesn't move.

Since the speedometer is working, there could be a possibility that the solenoid is not spinning the shaft to turn the odometer gears.. Anyone experienced this before?

[rustneversleeps]

i have the same problem as Fabe speedo works and repaired with new gears triple checked every thing, but odometer still not working..
ever thing else works fine..