MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
Where is the fuse box on the Mercedes-Benz R-Class? Whether looking for the cigarette lighter, radio, COMAND, or Navigation fuse location, here you will find a list of all the fuses on your R-Class.
The W251 R-Class shares its platform and much of its electrical architecture with the W164 M-Class, so the panel layout follows the same logic.
- Engine bay, front SAM. Engine management, lighting, cooling and most front circuits.
- Side of the dashboard, passenger side. Behind the end cap, visible with the door open. Cabin circuits.
- Boot panel. Rear SAM circuits plus the relay board, which is where the trailer hitch, heated rear window, rear wiper and the power sockets are controlled.
Work out which end of the car the dead item is at before you start pulling trim. Anything to do with the tailgate, a trailer or the rear sockets is in the boot, not under the bonnet.
Two things make that worth saying on this model rather than just being boilerplate. The R-Class ran from 2006 to 2012 in most markets with a facelift in 2010, and allocations moved. And the W251 shares so much with the W164 M-Class that published charts for the two cars circulate interchangeably, including on this site, which is fine where the platform is genuinely common and misleading where the bodies differ, mainly the rear panels.
So use these charts to narrow things down, then confirm against the fuse allocation card fitted to your own vehicle before you pull or replace anything. Where the rear relay chart shows the same letter twice, that is build dependent, particularly whether the car has a trailer hitch and a rear wiper.
Press Ctrl and F, or Command and F on a Mac, and type the fuse number or the circuit you are chasing.
Where the Fuse Boxes Are on an R-Class W251
- Engine Bay ( Behind the headlight on the passenger side)
- Side of the dashboard. (Passenger side)
- Under the passenger seat. Fuses are next to the battery.
- In the rear, trunk on the passenger side.
Which Fuses the W251 Uses
The ATO and MAXI fuses are installed on the fuse box panels. All these fuses can be purchased on Amazon; links are provided below. They are inexpensive when purchased online.
Models and Years Covered
| Model: | R320 CDI R 320 BLUETEC R 350 R 500 R 63 AMG R 300 CDI |
| Years: | 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 |
| Chassis: | V251 W251 |
| Make: | Mercedes-Benz |
Interior Fuse Box
The interior fuse box is located on the side of the dashboard. You will find the fuse box on the passenger’s side of the dashboard. A plastic cover can easily be removed. Use a Dash Trim Removal Tool to avoid damaging the dashboard.
Fuse Box on the Side of the Dashboard, Passenger Side
| Fuse | Function, Purpose, Designation | Ampere |
| 10 | Blower motor Speed Control | 10 |
| 11 | Instrument Cluster, Dashboard | 5 |
| 12 | Air Conditioner Controls | 15 |
| 13 | Steering column, Upper control panel |
5 |
| 14 | Ignition EIS Control Unit | 7.5 |
| 15 | Media | 5 |
| 16-18 | Not used | – |
Fuse and Relay Panel in the Boot
Your Mercedes-Benz also has a fuse box in the trunk. To access these fuses, you must remove the cover in the luggage compartment.
Fuses in the Rear Panel
| Fuse | Purpose, Designation, Use, Function | Amp |
| 20 | Radio Antenna Filter | 5 |
| 21 | Control Unit N72/2 Â Rear center console switch module | 5 |
| 22 | Parktronics, Stationary Heater | 10 |
| 23 | COMAND, DVD, Radio, Stereo | 10 |
| 24 | Emergency Tensioner Right Front | 40 |
| 25 | COMAND, DVD, CD Changer | 15 |
| 26 | Door control Unit – Right Front | 25 |
| 27 | Passenger seat adjustment | 30 |
| 28 | Driver seat adjustment | 30 |
| 29 | Emergency Tensioner Left Front | 40 |
| 30 | Fuel Pump | 40 |
| 31 | Steering Wheel Heater | 10 |
| 32 | AIRMatic, Air Suspension | 15 |
| 33 | Keyless Go Remote Entry | 25 |
| 34 | Door control unit, Left front | 25 |
| 35 | Sound System, Amplifier, Subwoofer | 30 |
| 36 | Tele Aid | 10 |
| 37 | Backup Camera | 5 |
| 38 | Digital TV Tuner | 10 |
| 39 | Radio Tuner, Digital Broadcast, Tire Pressure Monitor |
7.5 |
| 40 | Easy Pack Liftgate, Rear hatch door closing | 30 |
| 41 | Overhead control panel | 25 |
| 42 | Panoramic glass sunroof | 25 |
| 43 | Fuel pump | 20 |
| 44 | Socket 12-volt front | 20 |
| 45 | Socket 12-volt rear | 20 |
| 46 | Cigarette lighter | 15 |
| 47 | Door sill molding lights/illumination | 10 |
| 48 | AdBlue Relay | 5 |
| 49 | Heated rear window | 30 |
| 50 | Liftgate wiper | 15 |
| 51 | activated charcoal filter valve | 5 |
| 52 | Emergency tensioner retractor left and right front | 5 |
| 53 | fuel pump | 5 |
| 54 | Front SAM, Headlight range adjustment |
5 |
| 55 | Instrument cluster, Light switch |
7.5 |
| 56 | AdBlue | 5 |
| 57 | Fuel Pump | 20 |
| 58 | Central Gate Way | 7.5 |
| 59 | Neck Pro Head Restraint | 7.5 |
| 60 | Glove light, Rear Sam Control Unit N10/8 Tele Aid, Comand APS |
5 |
| 61 | Restrain Air Bag SRS, Child seat recognition | 7.5 |
| 62 | Front Passenger and Driver seat adjust switch | 30 |
| 63 | Lumbar Support | 30 |
| 64-65 | Not used | – |
| 66 | Pneumatic motor for multi-contour seats | 30 |
| 67 | Air Conditioner Blower -Rear | 25 |
| 68 | Heated seat and steering wheel | 25 |
| 69 | – | – |
| 70 | Trailer hitch | 20 |
| 71 | Electric brake control for trailer | 30 |
| 72 | Trailer hitch socket | 15 |
Engine Compartment Fuse Box, Front SAM
There are fuses located in the engine bay. They are located right behind the headlight, on the passenger side.
Fuse Box in the Engine Bay
| Fuse | Function | Ampere |
| 100 | Wiper | 30 |
| 101 | Purge Control, Oxygen Sensor Upstream |
15 |
| 102 | Transmission Oil Pump | 10 |
| 103 | Engine Control Unit | 25 |
| 104 | – | 15 |
| 105 | Connector, ME Control Unit | 15 |
| 106 | Not used | – |
| 107 | Air Pump | 40 |
| 108 | Air Compress for Air Suspension | 40 |
| 109 | Electronic Stability Control ESP | 25 |
| 110 | Antitheft Alarm System, Siren | 10 |
| 111 | Direct Select | 30 |
| 112 | Headlights | 7.5 |
| 113 | Horn | 15 |
| 114 | Front SAM N10 | 5 |
| 115 | ESP | 5 |
| 116 | VGS | 7.5 |
| 117 | Distronic DTR | 7.5 |
| 118 | Engine | 5 |
| 119 | Control Unit | 5 |
| 120 | Engine | 10 |
| 121 | Heater | 20 |
| 122 | Engine Starter | 25 |
| 123 | Fuel Filter | 20 |
| 124 | Power Steering | 7.5 |
| 125 | Not used | – |
Relays in the Rear Panel
| K | Relay, circuit 15R sockets |
| L | trailer hitch |
| M | heated rear window |
| O | Circuit 15 relay |
| O | Fuel Pump |
| P | Rear Wiper |
| R | Circuit 15R |
| S | Front socket |
| T | Rear socket |
| U | Trailer Hitch |
| V | Spare |
Which Fuse Do I Need to Replace a Blown One
Your Mercedes-Benz uses automotive blade fuses. A box of 100 covering all the ampere ratings you are likely to need costs very little.
When replacing a blown fuse, use a fuse with the same ampere rating. The fuse rating is written on the fuse. You can verify that you are using the correct fuse by making sure the fuse colors for the blown fuse and the new fuse match. This indicates the same ampere rating.- Ensure that you close the fuse box cover properly and secure the tabs. This is very important to avoid any moisture getting inside the fuse box. The fuse box panel has a seal to keep water and moisture out of the box.
Fuses do not wear out. They blow because current exceeded the rating, so a blown fuse is a symptom rather than the fault.
- Blew once and the new one holds. An event. Note it and move on.
- The new one blows the instant you fit it. A dead short to ground, often where a harness crosses a bulkhead or runs near something that moves.
- Blows after a few minutes or only under load. A motor or component drawing too much as it heats up.
The fuse protects the wire, not the component, so a larger fuse only lets more current into a circuit that is already faulty. On an R-Class with a trailer hitch, a blown socket or hitch fuse is very often the trailer wiring rather than the car, so unplug the trailer and retest first.
Keep a fuse assortment and a test light in the car.
When the Fuse Is Fine and the Circuit Is Still Dead
On a W251 the fuse panels sit alongside the front and rear SAM modules, and most body circuits are switched by an output inside those modules rather than by a relay you can swap. So the fuse can test good, the component can be good, and nothing happens because the SAM output has failed. Like the W164 it shares its platform with, this car is also known for water reaching the rear SAM, so a rear circuit that died after wet weather is worth suspecting there before you chase wiring.
No scan tool can see a blown fuse. Nothing on the diagnostic socket can. What a scan tool does is read the SAM and report whether that channel shows an open circuit, an overload or a dead output, which is the difference between replacing a part and replacing a module.
The YOUCANIC UCAN-II Pro reads the front and rear SAM along with every other module on the W251, so you can tell a dead output from a dead component. It covers nearly everything XENTRY does apart from online VIN coding.
A SAM with a burnt output or water damage is a board level repair rather than automatically a new module. Module Medics repairs front and rear SAM units, which keeps your original part number and avoids the coding a replacement needs.
Related Reading
M-Class W164 Fuse Chart
The platform sibling, and the closest comparison for the R-Class layout.
GL X164 Fuse Chart
The third car on this platform, with its engine bay panel behind the headlight.
Understanding the SAM Module
What a failed SAM output looks like when every fuse tests good.
Where Is the OBD2 Port
Port location by model, for scanning the SAM.
