Two related E36 cluster faults come up constantly: fading pixels and a dead SI board.
- Fading pixels — the on-board computer/clock and odometer displays lose pixels or whole rows as the conductive film on the LCD ribbon degrades: missing segments, fading lines, eventually unreadable. The fix is a display/ribbon repair — the cluster comes out (a couple of screws, it tilts forward, disconnect the plugs) and the LCD's heat-seal ribbon is re-bonded or replaced (a common specialist service or careful DIY)
- Dead SI board — the service-interval/battery-backed board in the cluster; when it dies you lose the SI lights and sometimes the clock or other functions, often from leaked backup batteries corroding the board. Repairable by replacing the board or the soldered-in batteries
Removing the cluster is the same access for both. A totally dead display with the rest working points at the SI board or a connector; fading segments point at the LCD ribbon. Neither is a reason to buy a whole used cluster (which brings its own mileage/coding headaches) — repair the one you have.