speedometer

My speedometer has stopped working. It works every so often until about 2 months ago when it has not worked since. Any ideas. The Bentley book doesn't seem to have anything in there, or at least I couldn't find it. You bailed me out before with the turn signal, hoping to strike more gold. Thanks,

I assume you checked the fuse. Other than the speedo is any other instument not working? Is your radio working?

There are two possible problem areas: The sender located in the differential or the instrument cluster. Take a look at the connector in the differential and make sure that the connectors are clean and make a good connection. You can test it by moving the wheels and connecting a multimeter to the leads and you should see the signal increase and decrease (it is a toothed gear like the ABS sensors). If that part is ok then you might need to open up you cluster and see if you have bad solder joints. This one takes skill and time, patience and did I said time? I changed the whole board on mine as it was destroyed by the battery acid!

Good Luck!

My speedometer runs slow - about 6/10 of the actual miles (comparing to the GPS reading). Would you say it's the diff sending unit at fault? The rear differential was changed by the previous owner recently... Any ideas? Thanks!

Originally Posted by kkau

My speedometer runs slow - about 6/10 of the actual miles (comparing to the GPS reading). Would you say it's the diff sending unit at fault? The rear differential was changed by the previous owner recently... Any ideas? Thanks!

Sorry, just to clarify - the speed indicator works fine. COme to think of it, it may not be the sensor... It could be the speedometer drive gear problem. I would have to take it out and see... In any case, any helo would be appreciated! Thanks!

Originally Posted by kkau

Sorry, just to clarify - the speed indicator works fine. COme to think of it, it may not be the sensor... It could be the speedometer drive gear problem. I would have to take it out and see... In any case, any helo would be appreciated! Thanks!

Try it again - the oddometer is running 6/10 slower than the GPS. It will show 5.5 miles when actual it's 10 miles. Thanks.

Originally Posted by kkau

Try it again - the oddometer is running 6/10 slower than the GPS. It will show 5.5 miles when actual it's 10 miles. Thanks.

Some E28's have the typical problems that almost all old BMW's suffer from, worn cheap plastic gears. Bav Auto was selling some kits, but I'm not sure if they have them for your particular application. There's places that can rebuild them. If you do a search you might find out more. Mye28.com may be of some help also.

I have found hundreds of times that it's the speed sensor located in the diff.

It turns out to be the odometer gears - the small gear lost half the teeth, so it only turns 6/10 on a mile. I replaced the gears - works fine now. Except I don't see the oil pressure light come on (and I forgot whether it was working or not). All light bulbs are fine, so it may be the sensor, or connection somewhere... It's fun troubleshooting...