The Mercedes-Benz W246, the second-generation B-Class, debuted in 2011 and marked a major step forward in the compact MPV segment. Produced until 2018, it successfully combined family-oriented practicality with premium technologies and renowned German engineering quality.
Replacing its predecessor, the Mercedes-Benz W245, the W246 retained the distinctive sandwich-floor platform while adopting a completely redesigned, more modern look in line with Mercedes-Benz styling of that era. The model was offered with a wide range of engines, from fuel-efficient diesel units to turbocharged petrol options. Starting in 2014, a fully electric version—the B-Class Electric Drive (W242)—was also introduced.
The Mercedes-Benz W246, the second-generation B-Class, debuted in 2011 and became a major breakthrough in the compact MPV segment. Produced until 2018, it successfully combined family-car practicality with premium technologies and the renowned quality of German engineering.
Replacing the Mercedes-Benz W245, the W246 retained its distinctive sandwich-floor platform while adopting a completely redesigned exterior in line with modern Mercedes-Benz styling of that era. The model was available with a wide range of engines, from fuel-efficient diesel units to turbocharged petrol options. Starting in 2014, a fully electric version—the B-Class Electric Drive (W242)—was also introduced.
One of the standout features of the W246 was its impressive safety performance. It became one of the first vehicles in its class to achieve a 5-star rating in Euro NCAP crash tests. The model also offered a spacious interior with an adjustable load floor and a large luggage compartment.
As the number of electronic systems in modern vehicles continues to grow—from advanced infotainment to safety technologies—understanding the location and function of fuses becomes essential for any owner. The W246 is equipped with several fuse boxes:
- Interior fuse box – protects comfort systems, multimedia, lighting, and climate control
- Engine compartment fuse box – responsible for engine operation, safety systems, and exterior lighting
- High-power fuse block – protects energy-intensive systems such as the electric power steering and cooling fan
In this guide, you will find complete fuse tables for the Mercedes-Benz W246 with clear labels and descriptions to help you:
- Quickly diagnose and fix electrical issues
- Select the correct replacement for blown fuses
- Understand which systems each fuse protects
- Take into account differences between petrol, diesel, and electric versions
This guide will become an essential reference for W246 owners who want to maintain their vehicle independently and better understand its electrical architecture. Save these tables—they can help you save both time and money on diagnostics.
Interior Fuse Box and Relays for Mercedes-Benz W246
The interior fuse box is located underneath the glove compartment inside the cabin.
Mercedes-Benz W246 Interior Fuse Diagram – Full Fuse Assignment Guide
| № | Current strength | Description |
|---|---|---|
| 21 | 150A | Additional electric heater (vehicles with diesel engine) |
| 22 | 200A | Relay for additional battery ECO Start-Stop function |
| 23 | 30A | Front left door control unit |
| 24 | 30A | Front right door control unit |
| 25 | 30A | SAM control unit |
| 26 | 10A | End cable coupling for the additional battery of the “ECO Start-Stop” function |
| 27 | 30A | Engine compartment fuse and relay module |
| 28 | 5A | Electric Drive (W242): Thermal control unit |
| 29 | 15A | Trailer socket (until 02.11.2014) |
| 29 | 5A | Trailer detection control unit (from 03.11.2014) |
| 30 | 5A | Trailer detection control unit |
| 31 | 5A | All-wheel drive control unit |
| 32 | 5A | Signals from the steering column electronic module control unit |
| 33 | 5A | Audio module/COMAND system control panel |
| 34 | 7.5A | Climate control system control panel |
| 35 | 40A | Heated rear window |
| 36 | 7.5A | Driver’s seat control unit |
| 36 | 7.5A | Driver’s seat lumbar support adjustment control unit |
| 37 | 7.5A | Audio module/COMAND system display |
| 38 | 7.5A | Passenger restraint system control unit (Supplemental Restraint System) |
| 39 | 10A | Ceiling control panel |
| 40 | 15A | Transmission control unit (engine 651) |
| 40 | 5A | Electric Drive (W242): Transmission control unit |
| 41 | 30A | Panoramic sliding sunroof control module |
| 42 | 5A | Audio module |
| 42 | 5A | COMAND control module |
| 42 | 25A | Audio module |
| 43 | 5A | Parking assistance system control unit |
| 44 | 40A | Reversible front left seat belt tensioner |
| 45 | 40A | Reversible front right seat belt tensioner |
| 46 | 7.5A | Front passenger seat control unit |
| 46 | 7.5A | Lumbar support adjustment control unit for the front passenger seat |
| 47 | 7.5A | Navigation module |
| 47 | 25A | Adaptive damping system control unit |
| 48 | Reserve | |
| 49 | 7.5A | Drive Kit Control Unit for iPhone |
| 49 | 5A | COMAND fan motor |
| 50 | 5A | Camera cover control unit |
| 51 | Reserve | |
| 52 | 30A | Parking lock actuator motor signal |
| 53 | Reserve | |
| 54 | Reserve | |
| 55 | 5A | Telecommunications services communication module |
| 55 | 5A | KEYLESS-GO control unit |
| 56 | 10A | Signals from the steering column electronic module control unit |
| 57 | 30A | Multifunctional control unit for special vehicle |
| 57 | 7.5A | Multifunctional control unit for special vehicle |
| 57 | 5A | Relay terminal 87 parking lock actuator motor |
| 58 | 30A | Special purpose vehicle fuse box |
| 59 | 30A | Front passenger seat control unit |
| 60 | 30A | Driver’s seat control unit |
| 61 | 40A | Speaker system amplifier control unit |
| 62 | 20A | Electric steering lock control unit (711 transmission) |
| 63 | 25A | Fuel pump control unit |
| 63 | 5A | Electric Drive (W242): Transmission interface control unit |
| 64 | “Electronic Toll Collection” control unit | |
| 64 | DSRC toll data transmission control unit | |
| 65 | 5A | Glove box lighting ceiling |
| 66 | 15A | Special purpose vehicle fuse box |
| 66 | 5A | Special vehicle interface |
| 67 | Reserve | |
| 68 | Reserve | |
| 69 | Reserve | |
| 70 | 25A | Center console socket in the rear of the cabin |
| 71 | 25A | Socket in the trunk |
| 72 | 25A | Cigarette lighter with ashtray illumination in front |
| 72 | 25A | Socket in the cabin |
| 73 | 30A | Electric parking brake control unit |
| 74 | 30A | Electric parking brake control unit |
| 75 | 20A | Trailer recognition system control unit |
| 75 | 5A | Electric Drive (W242): Battery management system control unit |
| 76 | 25A | Trailer recognition system control unit |
| 76 | 5A | Electric Drive (W242): Parking lock control unit |
| 77 | 25A | Trailer recognition system control unit |
| 78 | 40A | Trunk lid control unit/tailgate drive control |
| 78 | 40A | Special purpose vehicle fuse box |
| 79 | 40A | SAM control unit |
| 80 | 40A | SAM control unit |
| 81 | 40A | Fan controller |
| 82 | 10A | Ceiling control panel |
| 83 | 7.5A | Electronic ignition lock control unit |
| 84 | 5A | Top control panel |
| 85 | 5A | EDW/towing protection/interior security system control unit |
| 86 | 5A | FM, AM and ZV antenna amplifier |
| 86 | 5A | Mobile antenna amplifier/compensator (from 01.06.2016) |
| 87 | 10A | Diagnostic connector |
| 88 | 10A | Instrument combination |
| 89 | 5A | Outdoor lighting switch |
| 90 | 5A | Intelligent radar sensor in the rear bumper on the left |
| 90 | 5A | Intelligent radar sensor in the rear bumper on the right |
| 91 | 5A | Pedal pressure control sensor |
| 91 | 5A | Footwell lighting switch |
| 91 | 5A | Electric Drive (W242): Battery management system control unit |
| 92 | 5A | Fuel pump control unit |
| 92 | 5A | Electric Drive (W242): Transmission interface control unit |
| 93 | 5A | Electric parking brake control unit |
| 94 | 7.5A | Passenger restraint system control unit (Supplemental Restraint System) |
| 95 | 7.5A | Occupancy recognition system and AKSE front passenger seat |
| 95 | 7.5A | Weight Sensing System control unit |
| 96 | 15A | Tailgate wiper motor |
| 97 | 5A | Mobile phone electrical plug connection |
| 98 | 5A | SAM control unit |
| 99 | 5A | Tire pressure monitoring system control unit |
| 100 | 5A | DIRECT SELECT interface (engine 133) |
| 101 | 10A | All-wheel drive control unit |
| 102 | 5A | Remote control receiver for autonomous heater |
| 102 | 5A | Transmission control unit (Electric Drive (W242)) |
| 102 | 5A | Driving mode control unit (AMG, from 01.09.2015) |
| 102 | 5A | Antenna switch for telephone and autonomous heater (from 01.06.2016) |
| 103 | 5A | Emergency call system control unit |
| 103 | 5A | Telecommunications services communication module |
| 103 | 5A | HERMES control unit |
| 104 | 5A | Multimedia interface control unit |
| 104 | 5A | Multimedia device connection module |
| 105 | 5A | Digital audio broadcasting control unit |
| 105 | 5A | Satellite Digital Audio Radio (SDAR) control unit |
| 105 | 7.5A | Tuner module |
| 106 | 5A | Multifunctional camera |
| 107 | 5A | Digital TV tuner |
| 108 | 5A | Rear view camera |
| 108 | 7.5A | Rear view camera (from 01.06.2016) |
| 109 | 20A | Electrical plug connection of the cargo socket |
| 110 | 30A | Audio module |
| 110 | 30A | COMAND control module |
| 110 | 30A | Motorsound control unit |
Relay
| Letter | Description |
|---|---|
| A | Relay terminals 15 |
| B | Rear window wiper relay |
| C | Relay terminals 15R2 |
| D | Rear window heating relay |
| AND | Relay terminal 15R1 |
| F | Relay terminals 30g |
| G | Electric Drive (W242): Relay terminal 87 parking lock actuator motor |
Note: Fuses 70, 71, and 72 are responsible for the cigarette lighter.
Fuses and relays Mercedes w246 (Mercedes) in the engine compartment
Fuses under the hood of a Mercedes W246
| № | Current strength | Description |
|---|---|---|
| 201 | 5A | Alarm siren |
| 202 | 20A | Autonomous heater control unit |
| 202 | 5A | Electric Drive (W242): Relay terminal 87 of the parking lock control unit |
| 203 | 15A | Front right headlight |
| 203 | 5A | Electric Drive (W242): Transmission control unit |
| 204 | 25A | Electronic stability control unit |
| 205 | 15A | Left horn |
| 205 | 15A | The beep is right. |
| 206 | 5A | CDI control unit (engine 651) |
| 206 | 5A | Transmission control unit (Electric Drive (W242)) |
| 206 | 5A | Brake booster vacuum pump relay (Electric Drive (W242)) |
| 206 | 5A | Relay electric circuit terminal 87M (Electric Drive (W242)) |
| 207 | 5A | Relay electrical circuit terminal 87M (diesel) |
| 207 | 5A | High-voltage battery cooling shut-off valve (Electric Drive (W242)) |
| 207 | 5A | Parking lock control unit (Electric Drive (W242)) |
| 208 | 7.5A | Relay terminal 87 (engines: 133, 607) |
| 208 | 5A | Electric Drive (W242): Fan motor |
| 209 | 15A | Front left headlight |
| 209 | Electric Drive (W242): Reserve | |
| 210 | 5A | Heated front window relay |
| 210 | 5A | Previous starter relay (from 03.11.2014) |
| 211 | 7.5A | CNG control unit (242.848) |
| 211 | 15A | Heating circuit circulation pump (Electric Drive (W242)) |
| 212 | 15A | Cable lug electrical circuit terminal 87M3 (engines 133, 270) |
| 212 | 15A | Ventilation duct heating element (engine 651) |
| 212 | 15A | Cooling system thermostat heating element (engine 651) |
| 212 | 15A | EGR cooler bypass valve (engine 651) |
| 212 | 15A | Lambda probe before the catalyst (engine 607) |
| 212 | 15A | Boost pressure control servomechanism (engine 607) |
| 212 | 15A | CDI control unit (engine 607) |
| 212 | 15A | Electric Drive (W242): Electric drive coolant pump and charger |
| 213 | 15A | Terminal 87 cable end sleeve (motors 133, 270, 651) |
| 213 | 15A | Hall sensor camshaft (engine 607) |
| 213 | 15A | CDI control unit (engine 607) |
| 213 | 15A | Dosing valve (engine 607) |
| 213 | 15A | Lambda probe after the catalystFuses and relays Mercedes w246 (Mercedes) high power, power |
And then the fuses of the high-power power unit.
High-power fuses Mercedes W246
Mercedes W246 high power fuses
The unit is also located in the engine compartment next to the relay and fuse block discussed above.
| Marking | Current strength | Appointment |
|---|---|---|
| F1 | 300A | Generator |
| F1 | 400A | Electric Drive (W242): DC-DC converter control unit |
| F2 | 200A | Interior fuse box (Electric Drive (W242), and cars with petrol engine) |
| F2 | 250A | Passenger compartment fuse box (diesel engines) |
| F3 | 100A | Electric power steering control unit |
| F4 | 40A | SAM control unit |
| F5 | 80A | Fan motor |
| F6 | 70A | Fuel heating control unit (engine 607) |
| F7 | 125A | DPF regeneration auxiliary heater control unit (engine 607) |
| F8 | 100A | Glow plug output stage module (engines: 651, 607) |
Relay
| Marking | Description |
|---|---|
| F32k1 | Relay isolation |
Owners of the Mercedes-Benz W246 often experience electrical issues, many of which are linked to fuses and relays. One typical problem is when the engine won’t start even though the instrument cluster is functioning. In many cases, this is caused by a faulty starter relay—commonly identified by markings such as “G” or “M” in the relay block located beneath the glove compartment. Swapping the relay with a similar one or replacing it can often resolve the issue. Another frequent fault is a blown cigarette lighter fuse (for example, fuse No. 72), which disables the cabin power outlet. Problems with systems like electric power steering, ESP, or other electronic components may also occur due to oxidized contacts in the fuse boxes or blown fuse elements.
When diagnosing electrical problems in the W246, a step-by-step approach is recommended. Start with a visual inspection of the fuses in the cabin (under the passenger-side dashboard) and in the engine compartment, using the appropriate fuse diagrams. Next, check the relays—especially those responsible for the starter and key power systems—by swapping them with known working units. It’s also important to measure the battery voltage, which should not drop below 12.0 V with the ignition on. If the issue remains unresolved, the cause may be more serious, such as worn starter brushes, requiring removal and repair of the starter.
Troubleshooting typically involves replacing blown fuses with ones of the correct rating, cleaning any oxidized contacts within the fuse blocks, and installing new relays if needed. In cases involving the starter, after verifying the relay, it may be necessary to replace the brushes or the entire starter unit. For more complex problems, such as locating a short circuit in the wiring, it is advisable to consult professionals experienced with Mercedes-Benz electrical systems.