Siemens BSM B3 is an engine compartment fuse and relay box (Boîtier de Servitude Moteur) primarily used in PSA Group vehicles like the Peugeot 206 Citroën C3
. Unlike standard consumer electronics, official internal schematics for the circuit board itself are not publicly released by Siemens; however, pinout data and functional diagrams for the external connectors are well-documented for repair and diagnostic purposes. Core Functionality & Variants
The BSM B3 acts as the primary power distribution hub for the engine bay. It contains several integrated relays that are soldered directly to the internal PCB, often encased in a protective gel compound to prevent moisture damage. Integrated Relays
: Includes controls for the fuel pump, cooling fan, headlights (low and high beam), and fog lights. Variant Comparison
: Often lacks the fog light relay (PTF), requiring an external relay or soldering if adding fog lights. : Features the integrated fog light relay as standard.
: Typically includes an additional fuse (F16) for the secondary air pump (catalyst air injection). Connector Pinout & Wiring
The module is identified by colored connectors (Black, Grey, Green) that interface with the engine loom and the interior BSI (Built-in Systems Interface). Key Pins / Functionality Black (28-pin) Main engine management, sensors, and actuator power. Grey (16-pin) Headlight controls, horn, and wiper power. Green (2-pin) High-current power supply from the battery. Key terminal paths include:
: Controlled via a specific internal relay, often the first point of failure for "crank but no start" issues. siemens bsm b3 schematic
: Communicates with the BSI to execute commands like turning on headlights or the AC compressor. Repair & Maintenance Guide Accessing the Board
: The casing is usually factory-sealed. Repairs require carefully cutting the plastic housing or using a heat gun and isopropyl alcohol to remove the thick silicone gel covering the PCB components. Common Failure Points
: Burnt relay contacts (especially the fuel pump relay) and corroded pins due to water ingress. Replacement : When replacing a BSM, ensure the number (e.g., 9643498880-00
) and the variant (B3) match exactly to ensure compatibility with your vehicle's features like fog lights or AC.
For detailed wiring diagrams of specific pins, you can consult technical resources on or community-led repair logs on Are you troubleshooting a specific electrical failure , such as a fuel pump or headlight issue? PEUGEOT 206 CC RC БЛОК BSM B2 B3 B4 B5 В ... - Drive2
The Siemens BSM-B3 (Boîtier de Servitude Moteur) is a vital engine bay fuse box and control module primarily used in PSA Group vehicles, including various Peugeot and Citroën models. It functions as a power distribution and protection hub, managing relays and fuses for critical engine systems. Technical Overview Manufacturer: Siemens (also manufactured by Delphi/PSA).
Primary Function: Manages and protects electrical circuits such as fuel pumps, headlights, wipers, and engine management components. Siemens BSM B3 is an engine compartment fuse
Operating Voltage: Typically ranges from 24V to 690V depending on specific industrial or automotive application.
High Interrupting Capacity: Capable of interrupting short-circuit currents up to 120kA. Schematic and Wiring Resources
Finding a detailed internal board-level schematic can be difficult due to proprietary designs, but the following resources provide wiring diagrams and pinout information:
Pinout and Connections: A comprehensive guide to the BSM-B3 connectors (labeled A through H) and their associated circuits (e.g., fuel pump, radiator fan relay) can be found in this Pinout BSI and BSM Guide.
Teardown and Wiring: For a visual look at the internal relays and fuses, the Citroën C3 Owners Forum offers a teardown and wiring diagram.
Internal Connections: Additional wiring logic for Peugeot 206 and 307 models is available in the Internal Connections Guide. Vehicle Compatibility
The BSM-B3 module (common part numbers: 9657608780, 9650618480) is typically found in: Peugeot: 206, 207, 307, 406, Partner. Citroën: C2, C3, C5, Berlingo, Xsara Picasso. Why the Schematic is Critical The BSM B3
BSM-B3 Siemens предохранители: особенности и ... - Олниса
The BSM B3 operates at high voltage (600V+ DC link). Unlike PLC logic troubleshooting, drive repair is dangerous and complex. The schematic provides:
Without the schematic, repairing a BSM B3 is blind guesswork.
Unlike cheap VFDs, the BSM B3 uses precision DC current transducers (or shunt resistors) on the output phases. On the schematic, look for low-ohm (e.g., 1mOhm) resistors in the emitter leg of the bottom IGBTs. These feed into a differential amplifier to send analog signals (typically 0-10V or 20mA) back to the control card for torque/current regulation.
While Siemens does not publicly distribute the full service manual for free (it is locked behind a Siemens Industry Online Support (SIOS) login, typically requiring a service contract), the general topology is standard. Here is what you will find on the siemens bsm b3 schematic:
After the optocoupler and isolated supply, the signal goes to a push-pull MOSFET pair (or a dedicated gate driver IC like IXDN609). This stage delivers peak currents of 2A to 6A to charge/discharge the IGBT gate capacitance quickly. The schematic will show:
Tracing this section allows you to measure the gate waveform directly at the output connector.
If you have the schematic, you can often repair the BSM B3 without original Siemens parts. For example:
However, never substitute the gate drive transformer—its turns ratio, inductance, and isolation rating are critical. Rewinding or replacing it requires exact specifications from the schematic.