The second generation of the Mercedes-Benz A-Class was introduced in 2004. The bodyshell was constructed from high-strength steel alloys bonded with structural adhesives, retaining the signature “sandwich” floor architecture from its predecessor. In 2008, the model received a mid-cycle facelift. This article provides comprehensive fuse box diagrams and relay assignments for the Mercedes-Benz A-Class W169 (2nd generation: A150, A160, A170) covering model years 2004 through 2012.
Below you will find fuse box locations, photos, and circuit diagrams. Fuses for the “Cigarette Lighter” and “Fuel Pump” are bolded for quick reference.
Passenger Compartment
The passenger compartment houses two power distribution and relay boxes protecting the primary electrical circuits.
Main Fuse Box
It is located in the front passenger footwell beneath the floor panel lining.
Overview of the Mercedes-Benz A-Class W169 passenger compartment fuse box.
| Fuse Diagram | ||
|---|---|---|
|
||
| No. | A | Description |
| 1 | 10 | Pre-facelift (up to 2008): Brake light switch |
| 5 | Code U58 (exterior light unit): Brake light switch | |
| 2 | 25 | Heated rear window |
| 3 | 7.5 | Instrument cluster |
| Electronic ignition switch (EZS/EIS) module | ||
| 4 | 15 | |
| Electronic steering lock (ELV/ESL) control unit | ||
| 5 | 7.5 | Heater control unit (HAU) |
| Automatic climate control panel (KLA) | ||
| 6 | 15 | Right horn |
| Left horn | ||
| 7 | 25 | Fuel delivery module with level sensor (Mercedes-Benz W169 fuel pump fuse) |
| 8 | 25 | Overhead control panel module (N70) |
| 9 | 40 | ESP and BAS control unit |
| 10 | 40 | Blower motor |
| 11 | 30 | M266 engine: Terminal 87 engine circuit relay |
| 40 | OM640 diesel engine: Terminal 87 engine circuit relay | |
| 12 | 5 | Steering column module (N80) |
| Multifunction steering wheel controls | ||
| 13 | 25 | Left front door control unit |
| 14 | 25 | Right front door control unit |
| 15 | 25 | ESP and BAS control unit |
| 16 | 10 | Data link connector (DLC / OBD-II) |
| Parktronic system (PTS) control unit (pre-facelift) | ||
| 17 | 5 | Exterior lighting rotary switch |
| 18 | 7.5 | Manual transmission (711, 716): Reverse light switch |
| 19 | 5 | Yaw rate and lateral acceleration sensor (AY) |
| 20 | 7.5 | Supplemental Restraints System (SRS) control unit |
| 21 | 30 | Starter motor relay |
| 22 | 7.5 | Instrument cluster (A1) |
| 23 | 20 | OM640 diesel engine (from 2008): Heated fuel filter with water sensor |
| 7.5 | Pre-facelift (up to 2008): Heated windshield washer nozzles | |
| 24 | 7.5 | Electric power steering (STEERCONTROL / ES) module |
| 25 | 7.5 | Brake light switch |
| ESP and BAS control unit | ||
| 26 | 7.5 | Automatic transmission (722.8 CVT): Electronic selector lever module (ESM) |
| 27 | 10 | Automatic transmission (722.8 CVT): Transmission control unit (AUTOTRONIC) |
| 28 | 5 | Exterior lighting rotary switch |
| 29 | 30 | Signal Acquisition and Actuation Module (SAM) |
| 30 | 25 | Terminal 87F circuit relay |
| 31 | 5 | Exterior lighting rotary switch |
| Central gateway / interface module (vehicles up to Nov 30, 2005) | ||
| 32 | 7.5 | M266 engine: ME engine control unit |
| 33 | 15 | Audio head unit |
| Audio module / Navigation control unit | ||
| COMAND system control and display unit | ||
| 34 | 25 | Left rear door control unit |
| 35 | 25 | Right rear door control unit |
| 36 | 10 | Facelift (from 2008): Parktronic system (PTS) |
| Trailer hitch recognition module | ||
| 7.5 | Pre-facelift (up to 2008): Trailer module | |
| Mobile phone interface connector | ||
| 37 | 7.5 | Supplemental Restraint System (SRS) control unit |
| Automatic child seat recognition sensor (AKSE / passenger seat) | ||
| Front passenger seat occupancy sensor | ||
| 38 | 25 | Front cigarette lighter with illumination fuse |
| 39 | 25 | Windshield wiper motor |
| 40 | 25 | Panoramic/louvered sunroof: Overhead control panel (sunroof motor) |
| 7.5 | Overhead control panel module (N70) | |
| 41 | 15 | Rear window wiper motor |
| 42 | 7.5 | Glove compartment lamp with microswitch |
| Left and right vanity mirror illumination | ||
| Dual pedal control sensor (driving school vehicle package) | ||
| Footwell lighting switch (driving school package) | ||
| VICS / ETC toll system power connector (Japan market) | ||
| Tele Aid emergency call control unit (US market) | ||
| 43 | 7.5 | M266 engine: Terminal 87M1e circuit supply |
| 15 | M266 engine: Terminal 87M1e circuit supply | |
| NGT bi-fuel engine: Terminal 87M1e circuit supply | ||
| 44 | 15 | M266 engine: Terminal 87M2e circuit supply |
| 20 | OM640 diesel engine: Terminal 87M2e circuit supply | |
| 45 | 25 | OM640 diesel engine: CDI control unit |
| 46 | 25 | Subwoofer (Japan market, facelift 2008+) |
| 40 | Audio amplifier (facelift 2008+) | |
| 7.5 | Universal Handy Interface (UHI) module (pre-facelift) | |
| GSM 1800 antenna compensator (pre-facelift) | ||
| Cellular phone module (Japan market, pre-facelift) | ||
| 47 | 7.5 | Mobile phone connector |
| Universal Handy Interface (UHI) control unit | ||
| Voice control system module (LINGUATRONIC, pre-facelift) | ||
| Cellular phone module (Japan market, pre-facelift) | ||
| 48 | 7.5 | Anti-theft alarm system (EDW) / tow-away protection / interior motion sensor |
| Anti-theft alarm siren | ||
| 49 | 25 | Upper control panel (UCP) |
| Pre-facelift: Left and right front seat heating | ||
| 50 | 7.5 | Media Interface (facelift) |
| Digital TV tuner (facelift) | ||
| DAB digital radio tuner (facelift) | ||
| CD changer (pre-facelift) | ||
| VICS / ETC power connector (Japan market, pre-facelift) | ||
| 30 | Special/taxi vehicles: Roof sign power supply | |
| Terminal 30 supply contact | ||
| 51 | 10 | Weight Sensing System (WSS) control module (Canada market) |
| Emergency signaling control panel (special service vehicles) | ||
| 52 | 7.5 | Tele Aid emergency call system (up to May 31, 2006) |
| 5 | VICS / ETC power connector (Japan market, up to May 31, 2006) | |
| 53 | 30 | Auxiliary 12V interior power socket |
| Rear cigarette lighter with illumination fuse (Mercedes-Benz A150, A160, A170) | ||
| 54 | 15 | Special service vehicles: 2-pin 12V auxiliary power socket |
| 25 | Pre-facelift: Audio amplifier / subwoofer | |
| 55 | 7.5 | Pre-facelift and facelift with Code 614 (Bi-Xenon): Left and right main headlights |
| 10 | Facelift: Left main headlight | |
| 56 | 10 | Facelift: Right main headlight |
| 57 | 15 | Facelift: Trailer hitch socket (AHV 13-pin) |
| 20 | Audio interface control unit (Japan market, pre-facelift) | |
| 7.5 | Tele Aid emergency call control unit | |
| SDAR satellite radio receiver module | ||
| 58 | 25 | Trailer recognition module |
| 59 | 20 | Trailer hitch connector (AHV 13-pin) |
| Trailer control module (vehicles up to May 31, 2005) | ||
| 60 | 20 | Driver seat multicontour / adjustment contact strip |
| 61 | 20 | Front passenger seat multicontour / adjustment contact strip |
| 62 | 40 | Facelift: Terminal 15 (2) relay circuit (optional equipment: xenon headlights, mobile phone) |
| 25 | Pre-facelift: Terminal 15 (2) relay circuit (optional equipment: xenon headlights, mobile phone) | |
| 63 | 7.5 | SDAR satellite radio module (Canada market) |
| 25 | Roof sign / light bar power feed (commercial/taxi vehicles) | |
| 64 | 40 | M266 engine: Secondary air pump relay |
| 80 | OM640 diesel engine: Glow plug output stage / controller | |
| 65 | 80 | Electric power steering (STEERCONTROL / ES) module |
| 66 | 60 | Signal Acquisition and Actuation Module (SAM) |
| 67 | 50 | Terminal 15R (2) circuit relay (optional equipment) |
| 68 | 50 | Standard equipment (facelift): Engine cooling fan with integrated controller (valid for M266.920 and M266.940 with 722.8 transmission). |
| 60 | Heavy-duty / optional cooling (pre-facelift & facelift): Engine cooling fan (valid for OM640.940/941, M266.960/980, and M266.920/940 with Code 550 trailer hitch) | |
| 69 | 50 | Terminal 15R (1) circuit relay |
| 70 | 60 | Terminal 15R (1) circuit relay |
| 71 | 150 | OM640 diesel engine: PTC auxiliary heater |
| 72 | 60 | Pre-facelift: Terminal 30 power distribution stud |
| Special service vehicles: | ||
| Fuse 7 (F7f7) circuit | ||
| Fuse 10 (F7f10) circuit | ||
| Taxi package: | ||
| Special vehicle multifunction module (MSS) | ||
Relay Box
Located behind the dashboard trim on the passenger side (K100 panel).
Access procedure:
1. Remove the trim panel beneath the glove compartment.
2. Remove the side trim panel adjacent to the door sill.
3. Peel back the footwell carpet section.
| K100 Relay Panel Layout | ||
|---|---|---|
|
||
| No. | Relay Assignment | |
| A | Terminal 15R (2) circuit relay (Optional Equipment) | |
| B | Terminal 15R (1) circuit relay | |
| C | Horn relay | |
| D | Heated rear window relay | |
| E | Windshield wiper stage 1/2 relay | |
| F | Windshield wiper ON/OFF relay | |
| G | Terminal 15 (1) circuit relay | |
| H | Reserved / Spare | |
| I | Secondary air pump relay | |
| K | Fuel delivery module (fuel pump relay) | |
| L | Engine control unit (Terminal 87) relay | |
| M | Starter relay | |
| N | Terminal 87F circuit relay | |
| O | Terminal 15 (2) circuit relay (Optional Equipment: Xenon headlights, mobile phone) | |
| No. | Location / Function | A |
| 80 | Passenger compartment power feed | 30 |
| 81 | 30 | |
| 82 | 30 | |
| 83 | 30 | |
Electrical System Component Locations
Overview of electrical component locations throughout the vehicle:
1. ABS / ESP control module;
2. A/C control unit integrated into climate control panel;
3, 4. Antenna signal amplifiers;
5. Left side-impact sensor;
6. Right side-impact sensor;
7. Anti-theft alarm system (EDW) control module;
8. Tow-away / inclination sensor (anti-theft system);
9. Anti-theft alarm siren (mounted on intake resonator);
10. Interior motion / volumetric sensors (anti-theft system);
11. Audio head unit / COMAND system;
12. Auxiliary heater control unit;
13. Vehicle battery;
14. Central gateway module (CGW / CAN bus);
15. Central locking infrared receiver (in driver door handle);
16. Data link connector (DLC / OBD-II);
17. Left front door control module;
18. Left rear door control module;
19. Right front door control module;
20. Right rear door control module;
21. Dashboard relay panel;
22. Main fuse box (passenger footwell);
23. Horns (behind front bumper);
24. Electronic ignition switch (EZS / EIS) control unit;
25. Immobilizer system (integrated into EZS control unit);
26. Immobilizer transponder antenna;
27. Turn signal / hazard flasher function (integrated into SAM / multifunction module);
28. Exterior light switch module;
29. Signal Acquisition and Actuation Module (SAM) connected to footwell fuse/relay box (controls interior/exterior lighting, horn, windshield wipers, central locking, power windows, turn signals, anti-theft alarm, sunroof, seat heaters, and immobilizer);
30. Multifunction steering wheel switches;
31. Steering column combination switch control unit;
32. Navigation system module;
33. Outside ambient temperature sensor;
34. Parktronic system (PTS) control module;
35. Electric power steering (STEERCONTROL) control unit;
36. Rain / light sensor (mounted behind interior rearview mirror);
37. Seat heating control unit;
38. Front passenger seat occupancy sensor;
39. Steering column module (N80);
40. Supplemental Restraint System (SRS / airbag) control module;
41. Cellular network transceiver / compensator module;
42. Mobile phone interface module (UHI);
43. Trailer recognition control module;
44. Transmission control unit (integrated in automatic gearbox);
45. Windshield wiper intermittent relay.
It's a good application and facilitates easy