INSTRUMENT LIGHT REPAIR

By Joseph C. Dille
BMWMOA #24754

Prior to the introduction of the /6 series of bikes BMW used point to point wiring for the instrument lighting. This type of wiring is simple, reliable and repairs are easy to make. However point to point wiring does have two drawbacks, it is labor intensive to assemble and is prone to wiring errors. With the new style of instruments on the /6 BMW introduced flexible circuit type wiring. With this method of wiring, copper foil circuitry is bonded to a flexible plastic substrate. This greatly reduces the assembly labor and eliminates wiring errors. Unfortunately, once damaged, the flexible circuit is difficult to repair.
The most common place for the flex circuit to fail is at tab that forms the instrument light contact.. The copper tends to crack from the combined effects of corrosion, vibration and the wear and tear of replacing bulbs. The failure cannot be repaired by soldering the tab back to the main circuit since the solder joint will be stiff and it will crack.

To repair this type of failure solder two pieces of copper braid to the existing circuit, then bend them down as shown in the picture. Solder Wick is the common trade name for this type of copper braid. It can be found at electronics supply stores like Radio Shack. First, carefully scrape the protective coating from the area above the break using a sharp knife. Then solder the end of the braid to main circuit where the coating was scraped away. Apply the solder sparingly or it will be drawn down the braid (that's why they call it solder wick). Replace the braid if it becomes filled with solder, since it will be too stiff to bend. Cut the pieces of braid to the same length as the tab and bend it into the hole. Then replace the bulb socket into the hole. The picture shows the completed repair with the braid sticking down into the top of the rectangular hole. The instrument light bulb is also shown

So far this repair has lasted one season, and I expect it to last many more. (As of November 1998 it has lasted almost 10 years)

Dille's Home Page

Visits