Mercedes-Benz C-Class W204 (2007-2014) uses a front SAM in the engine compartment, a fuse panel in the driver’s dashboard end, a rear SAM in the luggage compartment and two high-current power distribution blocks. Assignments vary with model year, engine, equipment and market. This article preserves all documented variants and spare positions.
Where are the W204 fuse boxes?
Front SAM: switch off the ignition, open the bonnet and remove the protective cover on the left side of the engine bay. This unit contains F1-F36 and its relays. Keep water away from exposed electrical modules.
Dashboard: open the driver’s door and carefully unclip the side panel at the end of the dashboard. The F116-F135 carrier is behind the cover. Some positions are used only with optional equipment or in earlier versions.
Rear SAM: open the luggage compartment and release the right-side trim access panel. The rear unit includes F37-F92 and related relays. Mercedes stores the car-specific fuse assignment card with the tool kit beneath the luggage compartment floor; consult it where ratings depend on the exact car.
Frequently checked W204 fuses
This quick list includes the front cigarette lighter, auxiliary power outlets, the fuel pump, radio and wipers. It should be cross-checked against the full diagrams and the vehicle-specific fuse card.
| Pozycja | Amperaż [A] | Chroniony obwód / funkcja |
|---|---|---|
| F71 | 15 | Front cigarette lighter / 12 V socket |
| F9 | 15 | 12 V outlet in glovebox |
| F76 | 15 | Additional 12 V socket |
| F72 | 15 | Luggage compartment socket |
| F42 | 20 | Fuel pump or fuel-pump controller |
| F10 | 30 | Front windscreen wipers |
| F49 | 40 | Heated rear window |
| F26 | 20 | Radio and COMAND |
| F16 do 05.2009 / F73 później | 5 / 7,5 | OBD-II socket |
The previous-generation Mercedes C-Class W203 fuse diagrams cannot be used for the W204, because the SAM architecture and fuse numbers differ.
Front SAM – engine compartment fuses F1-F36
This fuse box protects the engine controllers, ESP, SRS, starter, front wipers, audio / COMAND, horn and some sockets. CDI denotes the diesel engine controller while ME-SFI denotes petrol engine management, so the two assignments must not be conflated.
| Pozycja | Amperaż [A] | Chroniony obwód / funkcja |
|---|---|---|
| 1 | 25 | ESP control unit |
| 2 | 30 | Left front door control unit |
| 3 | 30 | Right front door control unit up to 31 March 2010 |
| 4 | 7,5 / 20 | Fuel-pump control / heated fuel filter sensor / headlamp control, engine and date dependent |
| 5 | 7,5 | Rear SAM, light switch from December 2009, or AMG rear differential cooling |
| 6 | 10 | CDI diesel controller or ME-SFI petrol engine controller |
| 7 | 20 | Starter via terminal 50 relay |
| 8 | 7,5 | SRS control unit |
| 9 | 15 | 12 V glovebox outlet |
| 10 | 30 | Front windscreen wiper motor |
| 11 | 7,5 | Audio/COMAND panel and display; optional navigation module |
| 12 | 7,5 | Climate control unit / overhead control panel |
| 13 | 7,5 | Steering column module; multifunction camera from March 2011 |
| 14 | 7,5 | ESP control unit |
| 15 | 7,5 | SRS control unit |
| 16 | 5 | Up to May 2009 OBD-II; optional phone, selector module and ECO start/stop transmission oil pump |
| 17 | 30 | Panoramic or electric sliding roof |
| 18 | 7,5 | Light switch / overhead panel / LIN power supply by year |
| 19 | 20 | Electronic steering lock and EIS/EZS ignition switch |
| 20 | 40 | ESP control unit |
| 21 | 7,5 | Brake-light switch, glovebox lighting and passenger seat occupancy detection |
| 22 | 15 | Engine / air-conditioning fan and engine controls depending on engine |
| 23 | 20 | Terminal 87, CDI or rear SAM depending on engine |
| 24 | 15 | Terminal 87, CDI or engine harness connections |
| 25 | 15 | Petrol ME-SFI; diesel oxygen sensor / emissions control, depending on engine |
| 26 | 20 | Radio / Audio 20 / Audio 50 APS / COMAND |
| 27 | 7,5 | EIS/EZS plus CDI or ME-SFI depending on engine |
| 28 | 7,5 | Instrument cluster |
| 29 | 10 | Right headlamp |
| 30 | 10 | Left headlamp; selected OM642 engine harness links |
| 31A | 15 | Left and right horns |
| 31B | 15 | Left and right horns |
| 32 | 40 | Secondary air injection pump on applicable petrol engines |
| 33 | 10 | 722.6 transmission controller / integrated VGS 722.9 |
| 34 | 7,5 | Fuel-pump controller on relevant versions and years |
| 35 | 5 | ESP controller on later versions |
| 36 | 7,5 | DISTRONIC / electrohydraulic steering assistance by version |
Engine compartment relays J-R
| Pozycja | Amperaż [A] | Chroniony obwód / funkcja |
|---|---|---|
| J | – | Terminal 15 relay |
| K | – | Terminal 15R relay |
| L | – | Spare relay |
| M | – | Terminal 50 starter relay |
| N | – | Engine circuit 87 relay |
| O | – | Horn relay |
| P | – | Secondary air injection pump relay |
| Q | – | Oil cooler fan relay / equipment-dependent circuit |
| R | – | Chassis circuit 87 relay |
For a front wiper failure, check F10 (30 A). F26 (20 A) protects radio / COMAND, while F31A and F31B (15 A each) are horn circuits. Check powertrain-specific positions against the engine code and build date.
Front high-current fuse blocks
Mercedes used different power distribution arrangements before and after updates to the electrical system. ECO start/stop is a major distinction. These high-current links must not be replaced using ordinary blade-fuse procedures.
Older main fuse arrangement
| Pozycja | Amperaż [A] | Chroniony obwód / funkcja |
|---|---|---|
| 88 | – | Pyrotechnic alternator / starter fuse |
| 89 | 125 | Front SAM |
| 90 | 40 | Rear SAM |
| 91 | 80 | Engine / air-conditioning cooling fan |
| 100 | 40 | Air-conditioning blower |
| 101 | 60 | Front SAM, selected petrol engines |
| 103 | 150 | PTC auxiliary heater on diesel versions |
| 104 | 70 | Interior fuse panel |
| 105 | 100 | Front SAM |
| 106 | 150 | Rear SAM |
| 107-110 | – | Spare positions |
Later main fuse arrangement without ECO start/stop
Later main fuse arrangement with ECO start/stop
| Pozycja | Amperaż [A] | Chroniony obwód / funkcja |
|---|---|---|
| 150 | 400 / 200 | Main power supply / pyrotechnic fuse, ECO start/stop dependent |
| 151 | 100 | Engine and air-conditioning cooling fan |
| 152 | 150 | Front SAM |
| 153 | 100 / 60 | Spare or front SAM on ECO start/stop cars |
| 154 | 60 / 150 | Front SAM or diesel PTC auxiliary heater |
| 155 | 50 / 100 | Spare / configuration-dependent |
| 156 | 150 / 100 | PTC heater or front SAM depending on version |
| 157 | 100 | Electrohydraulic power steering / spare |
| 158 | 50 / 150 | Blower regulator or rear SAM with ECO start/stop |
| 159 | 50 / 200 | Special-purpose vehicle controller / auxiliary battery relay |
| 160 | 60 / 50 | Spare or blower regulator with ECO start/stop |
| 161 | 100 / 50 | Front SAM or special-purpose vehicle controller |
| 162 | 100 / 60 | Spare position |
| 163 | 150 | Rear SAM, without ECO start/stop |
| 164 | 80 | Rear SAM, without ECO start/stop |
Positions 150-164 have vehicle-specific ratings and functions. A slash separates alternative original installations; it does not mean either fuse rating is acceptable on one car.
Driver-side dashboard fuse panel F116-F135
Remove the driver’s end-of-dashboard panel to reach the fuse carrier. Most optional seat and suspension systems were assigned different slots during the production run. Many sockets are correctly left vacant.
| Pozycja | Amperaż [A] | Chroniony obwód / funkcja |
|---|---|---|
| 116 | 30 | Driver seat controller up to 31 May 2009 |
| 117 | 15 | Adaptive damping controller (ADS) up to 31 May 2009 |
| 118 | – | Spare position |
| 119 | 7,5 | Rear climate blower up to May 2009; AMG Performance Media through June 2012 on selected vehicles |
| 120-122 | – | Spare positions |
| 123 | 10 | Steering column module |
| 124-125 | – | Spare positions |
| 126 | 30 | Front passenger seat controller up to 31 May 2009 |
| 127-128 | – | Spare positions |
| 129 | 20 | Oil cooler fan relay on M156 up to 31 May 2009 |
| 130-135 | – | Spare positions |
Rear SAM – luggage compartment fuses F37-F92
The rear module carries fuel pump control, seat adjustment, towing electronics, PRE-SAFE, media systems, heated rear glass and several 12 V power outlet circuits. Compare the installed box to both diagrams before selecting a fuse position.
Rear SAM variant 1
Rear SAM variant 2
| Pozycja | Amperaż [A] | Chroniony obwód / funkcja |
|---|---|---|
| 37 | 7,5 / 5 | SRS / NECK-PRO with model-year-specific rating |
| 38 | 15 | Rear wiper on applicable body style |
| 39 | 30 | Left rear door control unit |
| 40 | – | Spare position |
| 41 | 30 | Right rear or front door controller by year and market |
| 42 | 20 | Fuel pump / fuel-pump controller depending on engine and date |
| 43 | 7,5 | Rear climate blower from June 2009 if fitted |
| 44 | 30 | Right front seat adjustment |
| 45 | 30 | Left front seat adjustment |
| 46 | 7,5 | Antennas, alarm, interior / tow-away monitoring and KEYLESS-GO |
| 47-48 | – | Spare positions |
| 49 | 40 | Heated rear window |
| 50 | 50 | PRE-SAFE: right reversible front belt pretensioner |
| 51 | 50 | PRE-SAFE: left reversible front belt pretensioner |
| 52 | – | Spare position |
| 53 | 15 / 30 | Trailer recognition controller, date / version dependent |
| 54 | 7,5 / 15 / 5 | Trailer control or selected AMG seat functions, date and equipment dependent |
| 55 | 5 | AdBlue control unit on applicable diesels from June 2009 |
| 56 | 15 / 5 | Trailer module or socket, or selected AMG seat functions |
| 57 | 20 | Trailer recognition controller |
| 58 | 20 / 30 | Trailer recognition controller |
| 59 | 5 / 7,5 | PARKTRONIC / radar sensors, year dependent |
| 60 | 7,5 | Multicontour seat pneumatic pump |
| 61 | 40 | Boot / tailgate control unit |
| 62 | 30 | Driver seat memory controller from June 2009 |
| 63 | 30 | Passenger seat memory controller from June 2009 |
| 64 | 25 | DC/AC inverter if fitted |
| 65 | 15 | Adaptive damping controller |
| 66 | – | Spare position |
| 67 | 30 / 40 | Audio system amplifier by model year |
| 68 | – | Spare position |
| 69 | 20 | Rear subwoofer amplifier if fitted |
| 70 | 5 | Tyre pressure monitoring system (TPMS) |
| 71 | 15 | Front cigarette lighter / front 12 V outlet |
| 72 | 15 | Cargo-area socket / selected 115 V installations |
| 73 | 7,5 | Diagnostic connector / parking heater receiver from June 2009 |
| 74 | 15 | KEYLESS-GO |
| 75 | 20 | Auxiliary parking heater |
| 76 | 15 | Additional 12 V socket |
| 77 | 7,5 | Passenger seat occupancy / weight sensor WSS, selected markets |
| 78 | 7,5 | Ventilated front seats if fitted |
| 79 | 5 / 7,5 | Parking aid controller by year |
| 80 | 7,5 | Parking cameras and radar depending on equipment |
| 81 | 5 / 7,5 | Multimedia interface by year |
| 82 | 5 | Phone / TV tuner by market |
| 83 | 7,5 | eCall / TELE AID / reversing camera by market and year |
| 84 | 7,5 | Digital radio / reversing camera depending on equipment |
| 85 | 7,5 | TV tuner on selected markets |
| 86 | 7,5 | Rear entertainment DVD player |
| 87 | 7,5 | Emergency call system |
| 88 | – | Spare position |
| 89 | 20 | Trailer controller or M156 oil cooler fan |
| 90 | 40 | AdBlue power supply module on applicable diesels |
| 91 | 20 / 25 | DC/AC inverter or ECO start/stop transmission oil pump |
| 92 | – | Spare position |
Rear SAM relay positions A-G
| Pozycja | Amperaż [A] | Chroniony obwód / funkcja |
|---|---|---|
| A | – | Spare relay / variant-dependent circuit |
| B | – | Terminal 50 relay / variant-dependent circuit |
| C | – | Rear-window heater relay |
| D | – | Fuel-pump relay on relevant diesels |
| E | – | Rear wiper relay |
| F | – | Seat adjustment relay |
| G | – | Terminal 15R relay |
The common front lighter / 12 V outlet circuit is F71 (15 A), the rear-window heater is F49 (40 A), and F42 (20 A) serves the fuel pump or its control equipment on relevant engines. Different options may change the relay configuration.
Rear high-current pre-fuse assembly
These fuses feed major engine controllers and special-purpose electrical systems. Correct isolation and service procedures are required for high-current circuits.
| Pozycja | Amperaż [A] | Chroniony obwód / funkcja |
|---|---|---|
| 111 | 60 | Petrol ME-SFI or diesel CDI engine control unit |
| 112 | 80 | Special-purpose vehicle multifunction controller |
| 113 | 40 | M156 left and right fuel pump controllers |
| 114 | – | Spare position |
| 115 | 100 | Special-purpose vehicle multifunction controller |
Practical checks and model-year differences
Dead front cigarette lighter: inspect F71 in the rear SAM; the glovebox outlet uses F9 in the front SAM. Fuel pump not operating: check the car’s installed F42 circuit, fuel controller and associated wiring. Weak or absent blower: match the front pre-fuse block to the ECO start/stop configuration, then check the blower regulator.
Do not install a higher-amp fuse when the correct one keeps blowing. Wiring faults and overloaded components must be diagnosed. The later W205 uses a completely different arrangement, and the original W204 fuse card takes priority in engine-, equipment- or date-dependent cases.