The /6 and later bikes have an instrument cluster that uses a printed circuit board to make the connections between the large rubber block of the wiring harness that plugs into the back of the instrument housing and the lights inside the instruments. The copper foil traces can break over time resulting in one of more lights not lighting, or intermittently lighting.
I had a non-functioning dash light on this bike and used copper foil to repair the missing foil on the circuit board. It takes some patience to cut out a new trace from a piece of copper foil but it is not a hard repair to make
BMW no longer sells the circuit board although you can find used ones for sale on eBay and some are in good condition. However someone took the time and effort to design a replacement light housing and circuit board that uses LED lights instead of the original incandescent bulbs. For a badly damaged circuit board where the simple fix I made is insufficient, these replacement boards will likely do the trick. I’ve not had occasion to install one of these, but you will find information about them here:
I got some copper foil from a friend who makes stain glass windows. You can find copper foils sheets and rolls via a Google search. For example:
My foil did not have an adhesive back. I think adhesive backed foil strips would work as long as you make sure you solder the top of the copper to the pin it goes to.
Remove Instrument Cluster From Bracket
First detach the speedometer and tachometer cables from the back of the instrument housing. Then loosen the three bolts at the bottom of the housing that secure it to the instrument bracket in front of the handlebar mounts. These bolts are part of the instrument housing and slide into notches in the mounting bracket so don’t have to remove the bolts to slide the housing off the bracket. Pull the instrument housing toward the rear to reach the large black rubber block that plugs into the back of the housing. There is a small, recessed Phillips head screw in the center of the plug that attaches it to the instrument housing. Remove it enough to pull the plug out of the housing. Be careful with the plug as you can loose that small Phillips head screw. Here is the inside of the black rubber plug. You can see the pin numbers next to the holes.
Note that some holes do not have metal sleeves in them so the corresponding pins are not installed in the circuit board. The same connector was used for a number of years with changes in the instruments. Wiring to the the plug changed as changes were made to the lights and instruments inside the cluster.
Here is the back of the instrument cluster after it is removed.
In the center you can see the pins that the black plug connect to. Note the missing pins that match with the missing sleeves in the wiring harness plug. The plastic bush in the center is where the small Phillips head screw screws into. It’s common to find this bushing broken from stress created by pulling the rubber plug without removing the small Phillips head screw. It can be repaired with plastic epoxy or Plast-aid.
Disassemble Instrument Housing
A lot of screws are used to assemble the housing and mount the instruments. I like to those holding each piece into a separate container to make it easier to assemble the parts again.
I shot the pictures after I removed the speedometer and that’s why you can see the glass on the right side.
The outer cover comes off first.
Then the middle plastic cover that goes over the circuit board comes off exposing the pins.
The circuit board looks like a “T”. At the top of the “T” are two large bulbs that illuminate the face of the speedometer and tachometer. In the center, in a row, are all the indicator bulbs plugged into the back of the circuit board. The big bulb at the top of the leg of the “T” is the turn signal indicator. It was at the bottom of the leg of the “T” on the /6 bikes.
Remove the screws that attach the “T” shaped circuit board and the three colored wires that go to the electronic tachometer to remove if from the housing.
If you are working on an earlier instrument circuit board, it won’t have the three electronic tachometer wires on the side.
Here are all the housing parts from outside (top) to inside (bottom).
I carefully remove the bulb socket of the bulb that is not lighting from the circuit board by rocking it to one side to get it to release from the board. Go easy here because this is how the foil connector tab that contacts the leads on the holder get broken.
Here is the bulb holder with the side connectorthat contacts the copper foil on one of the plastic tabs the sit inside the bulb socket hole in the circuit board.
Here is the plastic tab that has the foil lead on one side. You can see the foil has broken off the plastic which is common when the foil gets corroded and the bulb socket is pushed in or out. Another common point of failure is at the crease of the plastic tab where it folds down into the hole in the circuit board. The foil can crack at the crease and that often results in intermittent bulb operation.
Repairing The Broken Copper Foil Trace
This bulb has short foil traces to the pins in the center of the circuit board. I cut some copper foil the length I need with a 90 degree corner, and taper one end to match the flexible plastic tab that fits inside the hole for the bulb socket. On the other end that goes the pin, I cut out a slot so the end will slide around the pin. Then I fold it.
I cut the other trace for the other tab. Then I tin the ends that go around the pins.
I bend the tapered ends of the foil over the end of the plastic tab. I make the end a bit long so I can fold it over the arrow point end of the plastic tab.
Then I solder the end of the trace to the bottom of the pin and put a dab of silicon seal on the plastic under the foil trace so it will stay in place.
Then I put the second foil trace on top of the plastic and solder the end to the pins at the base, and glue it to the plastic. Here are the repair foil traces soldered to the pins.
I installed the bulb socket and used an ohm meter to be sure there was a circuit between the two pins.I have continuity so the copper foil repairs are conducting electricity between the pins.
I put the circuit board back into the housing, attached the tachometer wires and then the center cover and finally the the back cover.