In a quiet garage, a Peugeot 307 sits silent, its headlights refusing to wake. The culprit isn’t a blown bulb, but a failure deep within its electrical brain: the Siemens BSM B3

The "S" or "Ref" terminal is used for the shield drain wire.

: It is common for users to upgrade a B2 to a B3 by soldering the missing internal relay and adding a 15A fuse to the existing PCB locations. Safety & Support

Contains a dedicated set of fuses (e.g., F1–F22) that protect circuits from electrical surges. Schematic and Internal Layout