Check the panel cover first and match each slot number with its assigned circuit to avoid removing the wrong protective element during inspection or repair. Use the printed chart inside the cover as the primary reference before testing any connection.
The electrical distribution unit is split between the engine compartment and cabin area, with separate groups handling lighting, control modules, and high-load components. Identify the correct panel location before proceeding, since similar layouts can cause confusion during diagnostics.
Each slot is rated for a specific amperage, typically ranging from 5A to 40A. Installing a higher-rated element can damage wiring, while a lower rating may lead to repeated failure. Always match the original rating stamped on the plastic body.
For deeper checks, use a multimeter to measure voltage across contacts while activating related systems such as headlights or climate controls. This method helps trace faults quickly and confirms whether the issue lies in the circuit or the connected component.
W245 Fuse Box Diagram with Relay Layout and Circuit Assignment Details
Use the cover insert to match slot numbers with circuits before removing any protective link, ensuring accurate identification of systems like lighting, control modules, and auxiliary electronics.
The electrical distribution panels are divided into engine compartment and cabin sections, each handling different load groups. High-current consumers such as cooling fans and ABS are placed in the front compartment, while cabin circuits manage switches, infotainment, and comfort systems.
Typical slot ratings include:
- 5A–10A for sensors and control units
- 15A–20A for lighting and accessory outlets
- 25A–40A for motors and high-load components
Relays are positioned alongside blade elements and control switching for systems that require higher current, such as fuel pump, starter circuit, and radiator fan. Identify each relay by its printed code and position within the panel grid.
To verify circuit operation, measure voltage at both contact points while the related system is active. A consistent reading indicates proper flow, while imbalance signals a break or failed link.
Inspect terminals for heat damage, oxidation, or loose fit. Discoloration or melted plastic indicates overload or poor contact pressure, requiring immediate correction.
For accurate tracking, follow this sequence:
- Locate the correct panel
- Match slot number with circuit list
- Check amperage rating
- Test voltage across contacts
Record verified assignments and keep them inside the panel cover to reduce diagnostic time and prevent incorrect replacements during future repairs.
Exact Locations of Fuse Boxes in W245 Engine Bay and Cabin
Open the engine compartment and locate the main power distribution unit near the battery on the right side, protected by a sealed plastic cover designed to prevent moisture and debris entry.
Release the locking tabs and lift the cover to access high-current circuits responsible for systems such as cooling fans, ABS, and engine control modules. Check the inner side of the cover for slot identification and circuit mapping.
Engine bay placement details
Positioned close to the battery, this panel minimizes voltage drop and supports high-load components through short wiring paths, reducing resistance and heat buildup.
Inside the cabin, locate the secondary distribution panel on the passenger side footwell area, hidden behind a trim panel or carpeted cover depending on trim level.
Remove the cover carefully to reveal circuits assigned to lighting, infotainment, climate control, and onboard electronics. Use a flashlight to clearly read slot numbers and assignments in low-light conditions.
Confirm both panel locations before diagnostics, as mixing them can lead to incorrect checks and unnecessary removal of working components.