If you own a 2014–2018 Smart Fortwo or Forfour (W453), knowing the fuse box layout is essential for quick and accurate electrical troubleshooting.
This guide gives you a clear fuse box diagram, helping you locate the right fuse for interior features, lighting, engine components, and other systems. Whether you’re fixing a blown fuse or diagnosing an electrical issue, this overview makes the process easier and more efficient.
Table of Contents
Cigar lighter (power outlet) fuse in the Smart Fortwo / Forfour is the fuse #12 in the Passenger Compartment fuse box.
Engine compartment
Main fuses (Battery clamp)
| Fuse Number | Description | Fuse Amp |
|---|---|---|
| F1 | Internal combustion engine: Electrical fuse 3A (F108f3A) and electrical fuse 3B (F108f3B) Electric vehicle: Power supply fuse and relay module (F1) DC/DC converter control unit | 200 |
| F2A | Vehicle interior fuse and relay module supply (F2) Protected through connector sleeve for circuit 30 Connector sleeve for circuit 30 | 70 |
| F2B | Electrical power steering control unit | 60 |
| F3A | Vehicle interior fuse and relay module supply (F2) Ignition lock Protected through connector sleeve for circuit 30 Connector sleeve for circuit 30 | 70 |
| F3B | Electronic Stability Program control unit | 50 |
Fuse/Relay Module
Assignment of the fuses and relays in the Engine Compartment Fuse/Relay Module (Internal combustion engine)
| Fuse Number | Description | Fuse Amp |
|---|---|---|
| 1 | Internal combustion engine relay module | Diode |
| 2 | Supply for vacuum pump relay (for USA) | Diode |
| 3 | Fuel pump with fill level sensor and temperature sensor | 20 |
| 4 | Supply for fused circuit 30 connector sleeve | 25 |
| 5 | Supply for connector sleeves for circuit 87 | 15 |
| 6 | Refrigerant compressor relay | 15 |
| 7 | Fan Through fan relay | 10 |
| 8 | Dual clutch transmission control unit | 10 |
| Relays | ||
| K1 | Engine function circuit 87 relay | |
| K2 | Fan relay | |
| K3 | Ignition coils/fuel pump actuation relay | |
| K4 | – |
Assignment of the fuses and relays in the Engine Compartment Fuse/Relay Module (Electric vehicle)
| Fuse Number | Description | Fuse Amp |
|---|---|---|
| 1 | Spare | – |
| 2 | Transmission mode recognition sensor Electric drive control unit | 15 |
| 3 | Electric vehicle drive motor fan relay | 40 |
| 4 | Battery cooling system coolant pumps relay | 30 |
| 5 | Battery cooling system coolant pump | 15 |
| 6 | Valid for electric vehicle: Battery management system control unit Electric drive control unit | 5 |
| 7 | Power electronics control unit power supply connector sleeve supply | 20 |
| 8 | Circuit 87 supply connector sleeve | 15 |
| Relays | ||
| K1 | Engine function circuit 87 relay | |
| K2 | Fan relay | |
| K3 | Ignition coils/fuel pump actuation relay | |
| K4 | Battery cooling system coolant pumps relay |
Rear Fuse/Relay Module
| Fuse Number | Description | Fuse Amp |
|---|---|---|
| 1 | Heated rear window over relay for heated rear window/outside mirrors | 30 |
| 2 | Internal combustion engine: Front passenger seat heater control unit Driver seat heater control unit Electric vehicle: Brake booster vacuum pump control unit | 30 |
| 3 | Supply for Electronic Stability Program control unit | 25 |
| 4 | Electric vehicle: Spare Electrical fuse 1 and electrical fuse 2 | 40 |
| 4 | Internal combustion engine: Sliding roof relay | 25 |
| 5 | Supply for internal combustion engine fuse and relay module | 60 |
| 6 | Internal combustion engine: Dual clutch transmission control unit Protected through connector sleeve for circuit 30 | 50 |
| 6 | Electric vehicle: Vehicle interior fuse and relay module supply | 40 |
| 7 | Fan motor Over fan relay | 30 |
| 7 | Fan solenoid switch ICE combustion engine cooling | 30 |
| 8 | Spare | — |
| 9 | Internal combustion engine: Secondary air injection pump (for USA) Electric vehicle: Heater for high-voltage battery Over heater relay for high-voltage battery | 60 |
| K1 | Fan relay |
Passenger Compartment
| Fuse Number | Description | Fuse Amp |
|---|---|---|
| 1 | Rear roof rack electrical connection | 20 |
| 2 | Spare | — |
| 3 | Spare | — |
| 4 | Spare | — |
| 5 | Driver-side SAM control unit | 25 |
| 6 | Driver-side SAM control unit | 25 |
| 7 | Driver-side SAM control unit | 25 |
| 8 | Center SAM control unit Radio Radio over connector sleeve for terminal 15 R | 15 |
| 9 | Spare | — |
| 10 | Horn | 15 |
| 11 | Battery sensor and driver-side SAM control unit | 5 |
| 12 | Front cigarette lighter with ashtray illumination | 15 |
| 13 | Spare | — |
| 14 | Internal combustion engine: Automatic transmission protected through connector sleeve for circuit 30 Diagnostic connector Electric vehicle: Fused circuit 30 connector sleeve Diagnostic connector | 20 |
| 15 | Supply for fused circuit 30 connector sleeve | 15 |
| 16 | Internal combustion engine Motor electronics protected through connector sleeve for circuit 30 Electric vehicle: Supply for fused circuit 30 connector sleeve | 5 |
| 17 | Supply protected through connector sleeve for circuit 30 | 15 |
| 18 | Brake lights switch | 10 |
| 19 | Outside mirror adjustment switch | 5 |
| 20 | Transponder coil Electronic Stability Program control unit and brake light switch Protected through connector sleeve for circuit 30 | 3 |
| 21 | Light functions protected through connector sleeve for circuit 30 | 10 |
| 22 | Steering wheel angle sensor Dual-clutch transmission control unit | 5 |
| 23 | Spare | — |
| 24 | Center SAM control unit | 15 |
| 25 | Center SAM control unit | 10 |
| 26 | Center SAM control unit | 15 |
| 27 | Center SAM control unit | 20 |
| 28 | Driver-side SAM control unit | 10 |
| 29 | Driver-side SAM control unit | 10 |
| 30 | Combination switch Alarm siren Supply for fused circuit 30 connector sleeve (Electric vehicle) | 15 |
| 31 | Instrument cluster and additional instruments | 10 |
| 32 | Spare | — |
| 33 | Supplemental Restraint System control unit | 5 |
| 34 | Combination switch | 5 |
| 35 | Electrical power steering control unit | 5 |
| 36 | Center SAM control unit | 5 |
| 37 | Driver-side SAM control unit | 30 |
| 38 | Air conditioning power supply solenoid switch | 40 |
| 39 | Internal combustion engine Starter, Through starter relay | 30 |
| 39 | Electric vehicle: Blower motor | 40 |
| 1/1 | Electric vehicle: Electric vehicle circuit 30 connector sleeve supply | 10 |
| 1/2 | Electric vehicle: Brake booster vacuum pump control unit Power electronics control unit | — |
| 1/3 | Spare | — |
| 1/4 | Sound system amplifier control unit | 20 |
| 1/5 | Internal combustion engine: Dual clutch transmission control unit Electric vehicle: Electric drive control unit | 5 |
| 1/6 | Left front power window motor and right front power window motor | 25 |
| 1/7 | Left electrically adjustable and heated outside mirror and right electrically adjustable and heated outside mirror | 5 |
| 1/8 | Electric vehicle: Front passenger seat heater control unit Driver seat heater control unit | 25 |
| 1/9 | Spare | — |
| 1/10 | Electric vehicle: Steering wheel heater relay | — |
| 2/1 | Supply for soft top control drive unit | 20 |
| 2/2 | Supply for soft top control drive unit | 20 |
| 2/3 | Spare | — |
| 2/4 | Spare | — |
| Relays | ||
| K1 | Heated rear window/outside mirrors relay | |
| K2 | Front power window relay | |
| K3 | Sliding roof relay | |
| K4 | Front headlamps relay | |
| K5 | Starter relay | |
| K6 | Fanfare horn relay | |
| K | Electric vehicle: Steering wheel heater relay |
Also Read : How to read a car fuse box diagram? 5 Easy Steps
Frequently Asked Questions (FAQs)
My 12V power socket (cigarette lighter) is not working. Which fuse should I check?
This is the most frequently blown fuse due to overloading phone chargers and accessories.
Fuse Location: Check the Instrument Panel Fuse Box (Interior).
Fuse Type: Look for a fuse labeled “Accessory Socket,” “Cigar Lighter,” or “12V Socket.” It is typically a 15 Amp (Light Blue) or 20 Amp (Yellow) fuse.
My radio/media system display is frozen or black. Which fuse should I check to reset it?
While a software reset (holding a button combination) is often the first step, a fuse pull can force a hard reset.
Fuse Location: Check the low-amperage fuses in the Instrument Panel Fuse Box that control the media unit.
Fuse Type: Look for fuses labeled “Audio,” “Media System,” or “CAN Bus Gateway” (often 5 Amp or 10 Amp).
The blower motor for the heating/AC is not running at any speed. Which fuse protects it?
The blower fan is protected by a dedicated fuse.
Fuse Location: Check the Instrument Panel Fuse Box.
Fuse Type: Look for a fuse labeled “Blower Motor” or “Climatic Control.” This is typically a 30 Amp (Green) fuse. If the fuse is good, the blower motor resistor is likely the culprit.
My engine is overheating, and the cooling fan is not turning on. Is there a fuse for this?
Yes, the cooling fan circuit is critical for the rear engine and protected by a high-amperage fuse.
Location: Check the large fuses in the Rear Engine Compartment Fuse Block.
Fuse Type: Look for a large fuse labeled “Cooling Fan” or “Electric Fan.” If this high-amperage fuse is blown, the fan motor has likely failed, causing the fuse to trip.
My rear fog light or one side of the brake lights failed. Where are the fuses for the rear lights?
Fuses for the exterior lighting systems (excluding headlights, which are often in the interior box) are commonly found in the Rear Engine Compartment Fuse Block.
Location: Check the fuses labeled “Brake Light,” “Fog Lamp,” or “Rear Lights.” These are typically 10 Amp or 15 Amp fuses.