Audi A4 Fuse Box: Location & Guide
TL;DR
The A4 uses an engine-bay fuse box and an interior passenger-footwell fuse box on both the B8 and B9 generations; always confirm exact positions and amperage using the diagram printed on the fuse box lid.
Where the Audi A4 fuse boxes are located
Across the B8 (2009-2016) and B9 (2017-present) generations, the Audi A4 uses a two-box layout. The primary fuse box sits in the engine bay on the driver's side, close to the battery or strut tower, under a black plastic cover secured by clips or quarter-turn fasteners. The secondary fuse box is inside the cabin in the passenger footwell, tucked behind a small trim panel on the lower side wall that pulls away by hand. Some higher-content trims and later B9 model years route additional relays through a compact panel near the driver's seat base for equipment like the fuel pump or seat heaters. Because exact box count and trim placement can shift slightly by trim and model year, always verify against the diagram on your car before pulling any fuse.
| Generation / years | Fuse box | Location | How to access |
|---|---|---|---|
| B8 (2009-2016) | Engine compartment box | Driver's side of engine bay, near battery/strut tower | Unclip or twist the black plastic cover latches, lift straight up |
| B8 (2009-2016) | Interior box | Passenger footwell, lower side panel | Pull trim panel by hand from its clip points, no tools required |
| B9 (2017-present) | Engine compartment box | Driver's side of engine bay, near battery/strut tower | Release edge clips/fasteners, lift the cover off |
| B9 (2017-present) | Interior box | Passenger footwell, lower side panel | Pull trim panel by hand; some trims use one retaining screw |
Finding the official fuse legend
Do not rely on memorized fuse-number lists, because assignments shift by engine, market, and options package. The authoritative fuse legend is printed on the inside of each box's lid as a small diagram, and the same layout is reproduced in the owner's manual electrical/fuses chapter. Match the fuse's physical position on the lid diagram to the fuse in the box before you touch anything.
Fuses that commonly blow and their symptoms
- Cigarette lighter / 12V accessory outlet: outlet stops charging phones or powering accessories while everything else works normally.
- Radio / infotainment (MMI) circuit: screen stays black, system won't power on, or it resets repeatedly.
- Interior lighting circuit: dome light, footwell lights, or glovebox light stop working together.
- Blower motor circuit: HVAC fan produces no airflow on any speed setting, though the climate controls still respond.
- Fuel pump relay/fuse: engine cranks but won't start, or it stalls and won't restart, since the pump loses power.
Checking and replacing a fuse safely
Turn off the ignition first. Pull the suspect fuse straight out with the plastic fuse puller usually clipped inside the cover, and hold it up to light: a broken or blackened internal wire strip confirms a blown fuse. For a clearer check, use a test light or multimeter across the fuse terminals with the ignition on. Replace only with a fuse of the identical amperage rating shown on the lid diagram; a higher-rated fuse can allow excess current to damage wiring or components.
When a fuse keeps blowing
If a freshly replaced fuse blows again immediately or after only light use, that circuit almost certainly has a short or an overloaded component rather than a simple worn-out fuse. Continuing to replace it with a higher-amp fuse is unsafe. In this situation, having the vehicle's stored fault codes read is the fastest way to identify which module or wiring segment is drawing excess current, since the control module often logs a related electrical fault before or when the fuse fails.
Summary
| Engine-bay fuse box location | Driver's side of engine bay, near battery/strut tower |
|---|---|
| Interior fuse box location | Passenger footwell, lower side trim panel |
| Generations covered | B8 (2009-2016) and B9 (2017-present) |
| Fuse legend source | Diagram printed on fuse box lid + owner's manual |
| Common problem circuits | 12V outlet, infotainment, interior lights, blower motor, fuel pump relay |
| Replacement rule | Match amp rating exactly, never go higher |
| Repeat blown fuse | Indicates a short - scan stored fault codes |
Full diagnostics
For the complete step-by-step diagnostic and repair guide, see Audi A4: Common Problems, Fault Codes & Repairs.
Frequently asked questions
Where is the main fuse box on an Audi A4?
On both the B8 (2009-2016) and B9 (2017-present) Audi A4, the main fuse box is in the engine bay on the driver's side near the battery and strut tower, under a black plastic cover held by clips or twist fasteners. A second fuse box is inside the cabin in the passenger footwell behind a small removable trim panel.
How do I know which fuse controls which function on my A4?
Do not guess from memory or generic lists, because fuse assignments vary by engine, trim, and model year. Open the fuse box lid: a printed diagram on its underside shows the exact fuse-to-function map for your specific car, and the same diagram is repeated in the owner's manual electrical section.
Why does my Audi A4 cigarette lighter or 12V outlet not work?
A dead 12V accessory outlet on the A4 is almost always a single blown fuse dedicated to that circuit, especially if other systems work fine. Locate that fuse using the box lid diagram, confirm it is blown by holding it to light or testing it, and replace it with a fuse of the same amperage rating.
Why does a new fuse keep blowing on my A4?
A fuse that blows again right after replacement signals a short circuit or an overloaded component on that circuit, not a bad fuse. Do not install a higher-amperage fuse to work around it. Have the car's stored fault codes scanned, since this often points directly to the faulty module or wiring segment causing the repeat failure.