speedo at 0 mph-advice please

[matt86]

Hi my speedo dropped to 0 mph and stayed there ever since the other day, is this a bad connection on the odometer, bad sensor?

Any advice on how to /fault find and resolve would be appreciated.

Cheers

Matt

[DanThe]

Check the diff sensor plug and cables, its common for them to corrode and break

[matt86]

cheers mate, will have a look on the ramp at weekend.

[Brianmoooore]

It's not corrosion that causes the most common failure - it's a phenomenon known as "work hardening" where the copper of the wires becomes brittle as a result of vibration from the diff causing changes to its crystalline structure .
This often causes the wire to break internally in the vicinity of the diff., with nothing visible externally. Gently pulling the wire will identify the site of the break by seeing where the plastic sheath stretches.
Because the "work hardening" is irreversible, except by heating the wire to red heat, the last 300mm of wire to the diff, including the plug buckets, should be replaced, rather than a repair attempted.

[jimbob29]

Is ther a wiki about none working speedometers??

[Ranchero]

Not really. It just goes as far as to reiterate what has already been said about replacing the diff sensor plug and about 30cm of the attendant wiring.

Another possibility is that the instrument cluster is at fault, particularly if the speedo only works intermittently.
Check out the link below. Probably explains things better than I ever could.

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

You'll need to be handy with a soldering iron to do this.

[matt86]

Cheers guys for the useful info

[magpie]

i have a spare diff sensor and plug if needed

[LLamaFarm]

mine did it when i first got car, tapped it and it shot back up, was a dodgy connection behind speedo, other place to check as mentioned is the two wires going into your diff

[Rtaylor2208]

Does the economy guage work? If not one other thing is the fuse, cant remember exactly which one something like 11 or 14. Best to double check them first as its quick and easy before having to get under the car or take anything apart.