E30 speedo not working

[Jakebooth2015]

Just started using my e30 but the speedo no longer works did when I first got the car but nothing now although the mpg gauge dose still work but doesn't show a correct reading goes up to 50 when putting your foot down but settles at 0 didn't know if any one else has had this problem any help would be much appreciated

[sadham]

My speedo works sometimes and flickers up and down most the time. From what I've read I believe it may be done to the sensor in the rear diff? Give it a clean and check?

[jimbom30cab]

i'd check the wiring to the connector on the back of the diff.

[Brianmoooore]

Not the sensor itself, but the wire leading to it. If you probe around, you will probably find a broken wire, which might be still inside the outer insulation.
Copper (wire) has a peculiar characteristic that if it is subjected to vibration it gradually changes from a soft, ductile metal into a hard and brittle one, and the vibrations from the diff. are sufficient to cause this change. For this reason, the last 300mm or so, at least, of the wire, complete with plug, needs to be replaced and not just repaired.
BMW can supply a repair section of wire, or you can use a section of wire and identical plug from the headlight wiring of a scrap E30.
There is another, less common, fault that affects the speedo, where a particular solder joint cracks inside the speedo, but this can usually be identified if you hit the top of the dash, when the speedo will normally burst back into life for a short period.

[Jakebooth2015]

Ok will give this ago tomorrow and see what happens thanks