Here is a challenge for the BMW trivia buffs. I took the IC out of my 1990 325ic to work on the printed circuits (re-flow solder) and discovered a wire (blue/green) with a rubber cap on the end disconnected. This wire end is rectangular in shape and has a tiny metal post next to a hole as the end piece. I suspect it connects to the back of the green box at rear of cluster and behind the speedometer (part BMW137218) that has three vertical ports capable of holding this electrcal connector, but which one of the three (top/middle/bottom) I connected to the bottom port and put IC back in and the car ran with no apparent problems. I am confused, and my tech Sam Adams is confused. Can you help me?

I have tried connecting the lead to all 3 ports but have found no apparent use for the wire, my odometer doesnt work thought it might help fix the problem but with no luck . Also have found the wire connected to the port toward the back of the green connector on salvage vehicles .

Had a BMW Master Tech tell me that this wire connects to the top port on back of green box behind speedometer and is the input for the cruise control. I hooked it up and CC works. Now if I could find out what the blue wire that dangles just below my lower instrument cluster panel, drivers side hooks to, I might be happy.

The model i have doesnt have CC, could be why i havent noticed any difference .lol. but the info was useful. I found the gears in both of the odometers i have are crumbling apart so now i need to find a cluster with good gears . Ty for the info . Also i found 2 blue wires behind the cluster with mini bulb sockets on them? not sure if there the same u are talking about .

most of the time the area behind the cluster you are descibing is for a speed signal output from the cluster. it can go to cruise control , like has been mentioned , or to the radio for speed dependand volume increase to compensate for wind and road noise in the vehicle.:eek: