The Service Interval (SI) display circuit board is removable on the E30 3 Series. Other vehicles have the Service Interval assembly as an integral part of the instrument panel.
Most problems with the SI stem from bad connections, faulty grounds, relays replaced with nonstandard non diode relays, or bad batteries. The circuit board can be exchanged or have the batteries replaced by soldering new tab batteries in place.
REMOVAL & ASSEMBLY
E30 3 Series
- Remove the instrument cluster.
- Disassemble the instrument cluster to separate the carrier from the instruments.
- Remove the screw holding the light guide at the center of the carrier assembly. Slide the Service Interval circuit board out.