MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
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In this guide (4 sections)
A W164 spreads its fuses across more panels than almost any Mercedes of its era, including two prefuse boxes, so a fuse number alone will not get you there. Start from what has stopped working.
- One item dead, interior. Passenger side of the dash, or the rear cargo area panel for anything at the back.
- One item dead, engine or chassis. Main fuse and relay box in the engine compartment.
- Several unrelated systems dead at once. A prefuse, not a fuse. There are two: one in the engine bay near the bonnet hinge on the passenger side, and one by the battery. A prefuse feeds a whole panel downstream, so one blown prefuse takes out everything behind it and looks like a catastrophic electrical failure.
- AdBlue or emissions warnings on a diesel. There is a separate fuse box on the rear left above the rear shock absorber, which most people never find because nothing else lives there.
That prefuse distinction is the one worth remembering. If you are staring at four dead systems and wondering what could possibly connect them, the answer is usually a single prefuse upstream rather than four faults.
Press Ctrl and F, or Command and F on a Mac, and type the fuse number or the circuit you are chasing rather than scrolling every chart.
Where the Fuse Boxes Are on a W164 M-Class
Fuse Box Locations at a Glance
- The main fuse box and relay box are located in the engine compartment.
- Rear, passenger side in the trunk.
- Inside the cabin. The passenger side of the dashboard.
- Prefuse box in the engine compartment. Near the hood hinge, passenger side.
- Prefuse box by the battery.
- The fuse box for AdBlue is located on the rear left, above the rear shock.
Models and Years Covered
| Model: | ML 320 CDI ML 320 BLUETEC ML 350 ML 500 ML 550 ML 63 AMG M-Class |
| Years: | 2006 2007 2008 2009 2010 2011 |
| Chassis: | 164 |
| Make: | Mercedes-Benz |
Fuse Box on the Passenger Side of the Dash
Several fuses are located on the passenger side of the dashboard in the cabin. Remove the plastic cover using Trim & Panel removal tools to avoid damage.
| Fuse | Purpose, Designation | Ampere |
| 10 | A/C Air Conditioner, Fan / Blower Control | 10 |
| 11 | Instrument Cluster | 5 |
| 12 | Air Conditioner Control Unit | 15 |
| 13 | Steering Column,
Upper control panel |
5 |
| 14 | Ignition, Electronic Control Unit, EIS N73 |
7.5 |
| 15 | Compass, Media Interface |
5 |
| 16-18 | Not Used |
Fuse Box in the Rear Cargo Area
A second fuse box is located in the cargo compartment on the passenger side. You must remove the cover by twisting the two locking tabs to access these fuses. Here you will find relays and fuses 20 through 72.
| Fuse | Purpose | Ampere |
| 20 | Radio Antenna filter | 5 |
| 21 | Aux, RCP | 5 |
| 22 | Parktronic, Radio Remote Control |
5 |
| 23 | DVD Player, Bluetooth |
10 |
| 24 | Emergency tensioning retractor | 40 |
| 25 | COMAND, DVD changer, Radio, Stereo | 15 |
| 26 | Door control, Right front door. | 25 |
| 27 | Seat adjustment and memory, Passenger front. | 30 |
| 28 | Seat adjustment and memory, Driver | 30 |
| 29 | Emergency tensioning retractor left front. | 40 |
| 30 | Fuel pump, Folding rear seat, |
40 |
| 31 | Seat ventilation, Heated steering wheel |
10 |
| 32 | AIRmatic Air Suspension N51, if equipped with the adaptive dampening system. | 15 |
| 33 | Keyless Go Entry | 25 |
| 34 | Door control, Driver’s door | 25 |
| 35 | Sound system, Amplifier and subwoofer |
25 |
| 36 | Tele Aid, Emergency Calling | 10 |
| 37 | Backup Camera 12-volt power | 5 |
| 38 | Battery module, Digital TV tuner |
10 |
| 39 | Radio, Navigation, or Tire pressure monitor | 7.5 |
| 40 | Rear liftgate, rear door automatic closing | 30 |
| 41 | Overhead Control Panel | 25 |
| 42 | Overhead control panel | 25 |
| 43 | Fuel Pump | 20 |
| 44 | Power outlet, socket, 115V socket, cigarette lighter | 20 |
| 45 | Power outlet in the back by the second row | 20 |
| 46 | Cigarette Lighter Outlet | 15 |
| 47 | Door sill molding | 10 |
| 48 | Differential lock engages the unit, AdBlue relay |
5 |
| 49 | Heated rear window | 30 |
| 50 | Rear wiper | 15 |
| 51 | Charcoal canister shutoff valve | 5 |
| 52 | Emergency Tensioning Retractor | 5 |
| 53 | AIRmatic Air Suspension, Fuel Pump |
5 |
| 54 | Front SAM Control Unit N10 | 5 |
| 55 | Instrument cluster, Light Switch |
7.5 |
| 56 | AdBlue, Fuel Pump |
5 |
| 57 | Fuel Pump | 20 |
| 58 | Central gateway | 7.5 |
| 59 | Head restraint | 7.5 |
| 60 | Â Glove light, Engine Fuse and relays, Rear SAM Control Unit, Tele AID |
5 |
| 61 | SRS Airbag Restrain System | 7.5 |
| 62 | Passenger seat adjustment, front | 30 |
| 63 | Seat adjustment Front | 30 |
| 64 | Not used | |
| 65 | Not used | |
| 66 | Multicontour seat motor | 30 |
| 67 | Back A/C blower | 25 |
| 68 | Seat Heat, Seat Ventilation if equipped. | 28 |
| 69 | Differential lock, rear axle | 30 |
| 70 | Trailer Hitch Connection  Socket | 20 |
| 71 | Electrical Brakes for the trailer | 20 |
| 72 | Trailer hitch | 15 |
Relays in the Rear Cargo Area
| Relay | Purpose, Function |
| K | Power for the electric seat adjustment |
| L | Trailer hitch connection |
| M | Back window relay, heating. |
| N | Circuit 15 |
| O | Fuel Pump |
| P | Back Wiper |
| R | Circuit 15R |
| S | Power Supply |
| T | Power for the center and rear outlet |
| U | Trailer |
| V | Spare |
Engine Compartment Fuses
You will also find a fuse box in the engine bay, behind the headlight on the passenger side. To access the fuses, pull the two locking tabs forward. Once the two tabs are unlocked, lift the cover.
Engine bay fuses
| Fuse | Purpose, Designation, Function | Ampere |
| 100 | Windshield Wiper Motor | 30 |
| 101 | Purge Control Valve, CDI Control |
15 |
| 102 | Transmission oil cooler pump, Engine coolant pump |
15 |
| 103 | Engine Control Unit ME | 20 |
| 104 | Terminal | 15 |
| 105 | Engine Controls ME | 15 |
| 106 | not used | – |
| 107 | Air pump | 40 |
| 108 | AIRmatic Air Suspension | 40 |
| 109 | Electronic Stability Program ESP | 25 |
| 110 | Antitheft Alarm | 10 |
| 111 | Direct Select the Intelligent module | 30 |
| 112 | Lamps Headlamp Left and Right | 7.5 |
| 113 | Horn | 15 |
| 114 | Front SAM Control Unit | 5 |
| 115 | ESP | 5 |
| 116 | ||
| 117 | Distronic Unit | 7.5 |
| 118 | Engine Electronics ME Control Unit | 5 |
| 119 | CDI | 5 |
| 120 | Engine Control | 10 |
| 121 | Heater | 20 |
| 122 | Engine Starter | 25 |
| 123 | Fuel Filter Sensor | 20 |
| 124 | Power Steering, A/C Compressor | 7.5 |
| 125 | Electronics | 7.5 |
Relays in the Engine Compartment
| Relay | Purpose, Function, Designation |
| A | Wipers |
| B | Wiper ON/OFF |
| C | Coolant pump |
| D | Engine |
| E | Air pump |
| F | Horn |
| G | AIRMatic Compressor |
| H | Circuit 15 |
| I | Starter |
Resources and Useful Links
If you are missing the fuse chart and want a copy of the original fuse list for the car, look at this posting.
Which Fuse Do I Need to Replace a Blown One
Your Mercedes-Benz uses Automotive Blade Fuse Type. A box of 100 fuses that include all the different ampere ratings you need costs less than $20 on Amazon.
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 ensuring the fuse colors match the blown fuse and the new fuse. This indicates the same ampere rating.
Make sure to close the fuse box covers properly. It is important to do so to avoid moisture from entering the fuse box. Moisture can cause rust and electrical problems.
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. Keep a fuse assortment and a test light in the car instead.
When the Fuse Is Fine and the Circuit Is Still Dead
On a W164 most body circuits are not switched by a relay you can swap. They are switched by an output inside the front or rear SAM, so the fuse can test good, the bulb or motor can be good, and nothing happens because the SAM output has failed. These cars are also known for water finding the rear SAM, so a rear circuit that died after wet weather is worth suspecting there before you chase the 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 W164, 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
Understanding the SAM Module
What a failed SAM output looks like when every fuse tests good.
C-Class W204 Fuse Chart
Same era of Mercedes electrics, with a system by system lookup.
S-Class W221 Fuse Chart
Six panels and prefuses, laid out the same way as this car.
Where Is the OBD2 Port
Port location by model, for scanning the SAM.
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
