OBC and Tach died

[cosmo]

I had an occasional no start issue where the car would crank but not start, found there was no V+ at the coil and found the solder joints on the OBC relay were in bad shape.
Took it apart, cleaned all contacts and resoldered the joints.
That definitely fixed the starting issue and the car starts now every time without any issues.
However, now my Tach and OBC died (obc lights are on but won't display anything) tach stays at 0.
I am running MS, tach won't move even when simulating pwm out on the tach pin.
I checked fuses and none of them were blown, however fuse 21 was 30amps so I went ahead and replaced all fuses with the correct value. I'm afraid that maybe too much current went into the cluster and burned a trace?

Any idea what could be the culprit?

thanks!

[DesertBMW]

I had this problem and one trace on the cluster board burned up, I soldered it back, fixed the problem. Also cluster board can be bad

[cosmo]

Thanks, yeah I'll go ahead and pull the cluster to see what's up. I remember it smelled like something burned shortly after, but I was on the freeway in traffic, so it could've been anything really.

[cosmo]

Took the cluster apart, one trace on the PCB was indeed burned. Cleaned everything and soldered in a jumper, everything works great again. Thank you!

[earthwormjim]

Why did the trace blow in the first place? Something had to have caused a massive amount of current, and it is an on going problem, because someone put a 30amp fuse in fuse 21.

Perhaps check your SI batteries. The NiCad batteries present a short once they get very old.

[finnmole]

No tach or OBC

I had an intermittent tach but the OBC worked fine...figured it must be the SI batteries (after searching forums), removed the cluster adn replaced the nearly dead batteries...now no tach or OBC.
Looking at the wiring diagrams http://www.armchair.mb.ca/~dave/BMW/e30/e30_88.pdf
I can see S319 being a common splice point for the tach and OBC, also no trunk light, dome lights etc.
S319 is found near the pedals under the speaker (88 325 Is)
Surprised to find all the red/green wires are cut...looked factory.
Spliced it all together and everything works!

https://www.r3vlimited.com/board/attachment.php?attachmentid=126384&stc=1&d=1551672474

https://www.r3vlimited.com/board/attachment.php?attachmentid=126385&stc=1&d=1551672487