OBC help???

[NORCAL/E30]

I just purchased a used 13 button OBC for my 1990 325is. I just plugged it in and its not working. I was told by the person I bought it from that it was just pulled from another late model 325is and was in working order when taken out so I'm pretty sure the OBC is fine. I checked the fuse and it's cool as well. The only thing that puzzles me is a square shaped female plug with yellow wire that is seperate from the main OBC plug but still connected to the main bunch of wires. I can't seem to find out where this goes, or even find it's male partner for that matter. Can someone steer me in the right direction? :)

ABE

Edit: Here's a little more info. I just pulled the backlight and one of the bulbs is burnt out. Will this cause the OBC not to work?

[DaN]

ya if the lightbar is burned out, then you cant really see whats displayed.

[rs4pro3]

Yellow plug goes into the back of the instrument cluster

[NORCAL/E30]

Yellow plug goes into the back of the instrument cluster

Instument cluster as in where the gauges are behind the steering wheel? If so I think you might be mistaken or I'm not explaining this right. The wire I'm speaking of is the same loom as the large plug that connects to the rear of the OBC but is a separate single square plug. It won't reach over to the gauge cluster. I hope I'm not sounding like too much of an idiot. :oops:

ABE

[rs4pro3]

sorry I thought you said yellow plug not yellow wire. That lone yellow wire with the white plug dosn't go to anything.

[NORCAL/E30]

sorry I thought you said yellow plug not yellow wire. That lone yellow wire with the white plug dosn't go to anything.

So then either the OBC I was sent is bad as well or the one buld being out in the display window is the culprit. Anything else that could be wrong if these two problems don't fix it?

ABE

[Zoso]

I did the OBC retrofit not too long ago on my 1991 318i. For some stupid reason, I didn't purchase a replacement light bulb beforehand so I had to endure the OBC without a working light bar for several weeks before I had a change to get a new one and some time to install it and put the dash back together.

Even with the lightbar fried, I was still able to make out the information on the screen. Shine a flashlight at it (or better yet, remove the light bar and shine it in that hole). If you can't see anything, something besides the light bar is wrong.