posted Aug 22, 2012, 7:35 PM by Joseph Shearer [ updated Jul 27, 2015, 6:56 PM ] I own a 1996 BMW 328is and ever since I had the car, the odometer has not been working. This wasn't a big problem because my local mechanic, who my family has been going to for years, would over look the odometer and inspect the car. When I took my car to a different mechanic, they refused to inspect the car with the odometer not working, which is a $1000 repair for a new cluster. This problem has been know to be caused by corrosion of the solder on the pins that connect the odometer to the circuit board. The steps I took to repair the odometer are as follows:
This is the what the odometer looked like before the fix. It is clearly unreadable, even though comparing the last picture in the post and this picture you can see that the bottom lights that are suppose to be on are off and the ones that are off are semi-on.
1. Take the entire cluster out of the housing. To do this, unscrew the screws located at the top of the housing. Use a screw driver to get between the cluster and the housing and gently pop the cluster out. After this, you will need to unlatch the plugs connecting the cluster to the car's computer. This may be tricky so follow the diagram below.
2. Now that you have the cluster out you will need to get under the plastic case to the odometer to get to the connectors. You should notice that the plastic case is sealed with plastic rivets. If you break these, you will not be able to reconnect them unless you have a tool to place plastic rivets. The solution I came up with is to cut into the plastic case right above the odometer using a hot knife. Be very careful not to cut into the circuit board or the cluster will be ruined.
3. Now that the odometer connections are exposed, take a soldering iron and some solder and re-solder the connections back onto the board. After, the plastic piece that was cut off can be glued back onto the cluster.
4. Reconnect the cluster to the car and tryout the new working odometer.
For those who know more about digital displays and integrated circuits, they know that each digit has eight states that can be on or off. The digital displays I have worked with always use a chip to control the lights. It makes sense that if one part of the digital display doesn't work then the rest will not work either. In the case of odometers and stop watches, the digits are connected together in series in order to program them to read a consecutive list of binary code. If I find out more information on the exact pin that is causing the problem I will post about it in the future.
Saving $1000 this repair might cost $40 if you need to buy all the parts including screwdriver, knife, and soldering iron.
More posts will follow of easy fixes for BMW cars. In my experience they are the easiest cars to fix and parts online can be bought for reasonable prices.