e30 speedometer and obc turning off

[efficient]

So like my title says my obc and speedometer turn off at the same time. It usually works fine when I start the car but after like 10-15mins of driving I'll notice if the obc flickers on and off the speedo will bounce around and when the obc light turns off the speedo will completely die. I tried researching it but only found one thread like mine but no resolution. Every other Guage works just not my speedo and obc. My car is a 1986 eta with a 13 button obcif it matters. I looked at the diff wire and it was good.
I don't know where to look or were to start. Any suggestions?

[efficient]

Now my odometer and speedo both don't work. Guess they are both connected together.

[Das Delfin]

the speedo sends its signal to the obc via the wire that plugs into the green plug on the back of the cluster.. maybe something is shorting out in the obc? Try disconnecting the obc and see if it happens again. Or see if there is a fuse which powers the obc only and pull that

[dnguyen1963]

Check the solder on the main cluster board. It might need to be re-flown.

[Gregs///M]

Replace fuse 10, 12 and 21. They have common power, the fuses. They are also connected via signal wires but the signal path will not affect the OBC turning on and off. Old corroded, oxidized fuses will. Just replace with new 7.5A fuses.

[efficient]

I replaced all 7.5 fuses.not too long ago.

[ahlem]

Try banging on the dash right in the middle. I'm having the same problem and that makes things turn on again. I have a non-functioning OBC that needs to be changed. I took my cluster out and tightened the two nuts and checked the big ground but no fix. I'm going to examine the solder joints next. I do notice my Check light comes on anytime I turn on anything electrical. I will try cleaning other grounds to see if that helps.

[efficient]

Been banging on the dash but no effect. I don't think it's the batteries because I bought a refurbished batteries from gregs///M.
Turns on and off random. I'll put it another set of new 7.5 fuses on the 3 fuses that Greg said to change.
The nuts on the back were tightened and nothing.

[efficient]

Unplugged obc, now speedo works fine.

[Das Delfin]

^ ok so there's probably a short somewhere in your OBC. If you have a 6 button, now is the time for an upgrade!

[efficient]

It has 13 button. Don't think I'll be getting another obc.

[efficient]

So problem has come back. The needle bounces around everywhere

[Das Delfin]

Oh no.. Do they share the same power source? Grab a wiring diagram

But first try swapping clusters?

It's a long shot but how are your battery and alternator?

[Court M3]

Short, had this same problem. OP chech physical wiring behind cluster

[efficient]

Battery is maybe like 1 year and a half old. Alternator is like 2.5 years old.going to try another cluster and see what's going on.