Early 733i OBC Not Functioning

[mdrogersmdr2]

I know the answer likely is "your OBC is done", but here are the particulars: US 733i, 11/1982 build date, around 130K miles. OBC only diplays 0000 on battery connection (I do not get the .... reading at all). Clock will keep time after that in 24 hour mode but cannot be changed despite repeated pressing of the "time" button. No MPG, Avg speed. etc. I have replaced the 13 button display with the same result. Fuse and ground on the OBC are fine, there are no visible bad solder connections on the boards. Pulling fuse 27 results in the same 0000. It was not working when I got the car, after removing and reinstalling the fuse it worked for a few months then went into the current mode. Any suggestions? Thanks.

[Hit Man X]

Try another OBC1 box. It is in the driver kick panel.

[mdrogersmdr2]

Good idea. My son has a 533 and according to RealOEM the control units have the same P/N.

[Hit Man X]

Correct. Around 09/84 is the OBC2 break point.

[mdrogersmdr2]

Confirmed bad OBC1; worked fine with the known good box from an e28. Time for a WTB post.