My temp gauge and tach were not working so I replaced SI batteries but realised that there is a small repair done on pcb trace and some of the transistors are blown.
BMW E30 SI Board info and troubleshooting - Bavarian Restoration
x2 BMW E30 SI Board Batteries Sanyo FDK Instrument Cluster 1 Pair E23 E24 E28 | eBay
SI BOARD BATTERIES & CAPACITORS Repair Kit | MY Classic Parts | BMW Custom Accessories
VDO and Motometer E30 SI board Capacitor electronics and batteries (lithium battery board) | RTS - Your Total BMW Enthusiast
BMW E30 SI Board info and troubleshooting - Bavarian Restoration
New BMW 84-87 E23 E24 E28 E30 1.2-V Ni-Cad S.I. Board Battery (Batteries) | eBay
BMW E30 3-Series Service Indicator Battery Replacement(1983-1991) | Pelican Parts DIY Maintenance Article
SI BOARD BATTERIES & CAPACITORS Repair Kit | MY Classic Parts | BMW Custom Accessories
SI board batteries: did I do this right? - MyE28.com
BMW E30 SI Board info and troubleshooting - Bavarian Restoration
Bimmerforums - The Ultimate BMW Forum
BMW E30 SI Board info and troubleshooting - Bavarian Restoration
BMW E30 SI Board Batteries Sanyo / FDK Pair | TC European
Sanyo Lithium CR14250 Replacement Battery for E23 E24 E28 E30 E32 E34 Cluster SI-Board - Ivo Christov BMW E28 specialist
TCEuro - TCESIBATT - SI Board Batteries Sanyo/FDK Pair
ProgRama 62 11 1 394 268x BMW Cluster S.I. Battery board
BMW E30 SI Board info and troubleshooting - Bavarian Restoration