3 speedos changed and its still not working

[Kershaw]

i've swapped in 3 different clusters. 2 i clusters (a moto and a vdo) and an eta cluster (moto) and the tach will always work. but the speedo does not.

when i first got the car, just the tach would work. then, the speedo would work or the tach, but very rarely both. i pulled the cluster and replaced it (retaining the original speedo) and then everything worked great for 2 weeks. then the speedo stopped working. over the next 2 days it would occasionally work if i hit a bump or smacked the dash.

now it does not work at all.

how can i test (with a multimeter) if the speedo itself is bad. if the si battery were bad, the tach wouldnt work either, right? so... after 3 speedos im starting to think the problem is not in the cluster....

[Flash]

Have you checked the speed sensor in the rear cover of the diff?

[DTM190]

Sorry it doesnt answer your cluster question but something else that may help, on my 323i the wires where they go into the back of the cluster were hard and brittle and I ended up finding a few wires that were broken, replace a few inches of wire where they tend to bend when you put the cluster in and out and it sorted it. That was after musical clusters also.

[Kershaw]

i've checked to see that the speed sensor is still there on my diff. but thats it.

the wiring seems very malleable but i'll check it out.

[redhatpat]

The wires coming out of the speed sensor at the diff can go bad. They flex when the diff moves and over time will break. I had this happen on my car. I just replaced the plug and about 6 inches of wire.

[b*saint]

Yea I'd say its safe to say its not the speedo. I would figure speed sensor or harness.