e30 speedometer and obc turning off

[efficient]

Just swapped in another speedometer Guage and same thing. It bounces around.

[efficient]

i think i found an answer to my problem.
while i was driving around seeing if the problem was fixed after i swapped in new fuses for the 10,12,21 with new 7.5 fuses. the problem was still there. yesterday on the way to work i replugged the obc and it was still turning on and off.Today, i stuck my hand in and touched the white plug behind the cluster and moved the set of wire around, i could see my obc turning on and off and my speedo as well. so i think its a loose connection also i need to wrap those wires up so they aren't dangling around.

[efficient]

Going to update this.
I found out that the plug behind the gas gauge (white plug) the purple power wire is loose. So what I did was cut the plug off another car and soldered it onto my wire harness. When I soldered it on my speedometer, mileage counter, obc and mpg gauge all worked after driving around for less then a few hours it all stopped working. When I touched the wire behind the cluster it works again. I'm not sure what to do to get the wires to hold behind the cluster. Any suggestions?
So annoying to not have this working.

[T-Von]

I know this is an old thread but this forum really helped me diagnose my 1987 e30 325ic OBC/Speedometer issue. First, I’m very comfortable working on the cluster. I’ve replaced bulbs, odometer gears, batteries, barrel caps, etc. I’m also handy with a soldering iron. I’ve owned my e30 since 1995. It’s been my daily driver. It’s just a great vintage BMW that looks cool and is a blast to drive. Don’t know how many miles. Speedometer was replaced by my tech right after I bought it. Don’t guess he ever considered just replacing the gears. My cluster is a VDO. He replaced the speedometer with a Motometer speedometer which I found out when I replaced the gears my first time and bought VDO only to find out my tech had put a Motometer version in my VDO cluster.

I’ve since replaced the gears 3 more times. The odometer shows 87000 but it’s really more like 190,000 or more. Same motor! Trans rebuilt 5 years ago. Original alternator lated 30 years! LOL, No cracks on the dash. My issue was the OBC started pulsing and eventually started going blank. When it went blank the speedometer would also die. It became intermittent. During this issue the odometer gears went south so I decided to order new gears and research the OBC issue which led me here. I started the project early this morning and decided to try several things to resolve the OBC issue. I discovered that wiggling the white cluster connector made the OBC flash on and off.

So my original thought was a loose wire or corroded connections. Proceeded to take the white connector apart and check the connections. Everything looked okay. Buttoned it back up and the bad connection was still present. I did take some fine grit sandpaper to the pins but that did not solve the issue. Wiggling the connector made the OBC turn on and off. So I decided to take the cluster up stairs to my solder station and take a closer look at the plug pin pads on the cluster pcb. Visually everything looked okay. But my experience with solder pads tells me that a solder connection can look okay and still be bad. So I fired up the iron and reflowed some fresh solder onto the pcb pads being careful not to bridge them together.

Cleaned my work, buttoned it up and took it back to the garage and installed it. Plugged in all three connectors and the two wires for the cruise control and magically the OBC fired up very bright! Success! It was the 37 year old solder pads that were the issue. Nothing a dab of fresh solder couldn’t fix! Good ending to a long day. Saved myself a few hundred $$$ all with the satisfaction that comes with figuring out a nagging problem.