318i M10 Speedo not working....

Fri Feb 20, 2009 3:28 pm

Right then, what do i look for???

I could do with having the speedo working, due to the amount of speed cameras i drive through going to/from work!!

Is it likely to be the instrument cluster? (everything else works)

Is there a connection on the autobox i should check??

Any other causes???

Sun Feb 22, 2009 4:46 pm

The speedo in my 316i is temperamental, I'm pretty sure its the connector onto the back of the instruments as a sharp slap on the dashboard brings it back to life. I'm just too lazy to pull it all apart to have a look yet.

Sun Feb 22, 2009 5:21 pm

90% of speedo not working faults are as a result of an internal break in the wire leading to the sensor on the diff, caused by vibration.
The remaining 10% are mainly caused by a duff sensor in the diff, or by cracked solder joints on the speedo unit inside the cluster.

Sun Feb 22, 2009 5:30 pm

Brian.. In your experience, how much loom needs replacing when the wire is broken?

Sun Feb 22, 2009 7:26 pm

Change the last foot, and you'll be sure.
Get a piece of wire, complete with plug, from the headlamps of a scrap E30, or, IIRC, a repair lead is available from BMW.

Sun Feb 22, 2009 9:35 pm

Check the fuses as well...

My old m10 had a duff speedo - turned out to be the fuse!

Tue Mar 03, 2009 9:45 am

Just dragging this one up again now the car drives straight!!!

I reckon a fuse would be far too easy - any idea which one?? Surely it would affect other stuff too though??

Am i right in assuming you mean the break is most likely under the car near the diff?? If so, i'll crawl under and change it for a headlamp wire!!!

Looks like the scrap on my drive is finally coming in usefull!!

Fri Mar 06, 2009 9:24 am

Ok, have had a little poke about under the car - although i haven't replaced the cable, i did wiggle it about and reseat the connector. There was no corrosion on the plug and the cable looked ok, but obviously i wouldn't see if it was breaking down under the insulation.

I have realised that the mile meter is still working and ticking over as i drive!!! Would this indicate the cable is ok?? Surely it must use the same signal/connection??

Everything works fine except the speedo - am i really gonna have to crawl about on the floor to replace this cable, or would it more likely be something breaking down in the dash cluster??

Fri Mar 06, 2009 6:48 pm

If the odometer is still working, then the problem is on the speedo unit itself!

Fri Mar 06, 2009 8:13 pm

Coolio - saves crawling around to change that cable - would be a piece of cake on ramps, but on the kerb it's just a pita!!

Will swap the unit tomorrow morning (if i'm not too hungover!!) and see what happens!!

Sat Mar 07, 2009 12:10 am

In my '84 320i the speedo works only when it wants.

I noticed that it works properly when the cluster is hot (when the car is exposed to the sun, during summer for example), and sometimes for a few moments when the car is very cold.

The odometer does the same.

I think the wiring is ok...

Maybe the SI batteries?