Instrument Cluster Update
I recently removed the instrument cluster in the car because the digital display in the center of the tachometer was not working. Neither were the small instrument gauges, the SOC gauge and the Temperature gauge. Only the tachometer was working. I made a video over 9 years ago showing how I spoofed the instrument cluster to make all the gauges work. Video here. In addition to getting the gauges working again I also wanted to replace the speedometer. Last year I acquired several 120MPH speedometers on Ebay. The 80MPH speedometer that the car came with has always bothered me because the car is capable of moving much faster than 80MPH. The problem with the 120MPH speedometers were that they all had over 190k miles on the odometer. That could possibly be a problem when the car is inspected next time. The state records the odometer reading - mostly for insurance purposes. My 80MPH speedometer odometer only has 52K miles on it. I found a vendor that could do two operations on the speedometer. One was to reset the odometer to the value shown on the 80MPH speedometer odometer. The speedometer repair shop also calibrated the speedometer to work in my car. The 120MPH speedometers were used in European 320i BMWs that had a 4-speed manual transmission and a different rear-end gearing. Without modification the 120MH speedometer would ready about 15% faster. To use the120MPH speedometer with my rear-end gearing and have the correct speed shown on the speedometer a different gear was installed in the speedometer. The last step was to check the calibration.
When I took the instrument cluster out of the dashboard I found several loose wires. One was for the 7-segment digital display in the Tachometer. I have had problems with the 7-segment display getting easily damaged, but that was not the case with this display, I found another problem. I put the instrument cluster on the bench and replicated the wiring harness inside the car. I connected my LEVID (Legacy Electric Vehicle Instrument Driver) controller PCB and another GEVCU (Generalized Electric Vehicle Control Unit) PCB that I loaded with a test program. The test program replicated the CAN BUS messages in a continuous loop that come from the various components in the car like the Scott Drive controller and the current shunt. Below is an image of the testbench layout. The LEVID includes a Real Time Clock (RTC) and an isolation/driver circuit to output the serial data to the 7-segment display. I found that the isolation IC was damaged and that was what prevented the 7-segment display from working. I replace the IC and reset the RTC. The clock function now works on the 7-segment display as well as to display any of the instrument gauge data digitally.
The image below shows the cluster being tested with the CAN BUS data. All the instruments move and the 7-segment display shows the digital value of the tachometer. The tachometer is also new. The design with multiple colors came on later models of the 320i. That newer tachometer came with one of the instrument clusters I acquired that had a 120MPH speedometer. Shown is one of those 120MPH speedometers with the high mileage. When I sent the 120MPH speedometer to the shop for modifications I sent it in an instrument cluster that had a front plastic bezel that had no cracks or imperfections. As part of their service the speedometer shop polished the plastic bezel on that instrument cluster. The image below is my old instrument cluster that showed cracking on the bottom edge.
Shown
Shown below is the updated instrument cluster installed in the dashboard of the car. The SOC and Temperature gauges as well as the 7-segment display are all working and responding to inputs from the car. You can see how clear the view of the instruments is with the polished front bezel. You can see the fuel gauge on the left has a battery icon.
