Audi A4 Fog Lights: Specs, Fitment & Common Faults

On the A4, multiple lights failing together has genuinely been traced to a bad fuse box with several melted fuses inside — plus a confirmed Technical Service Bulletin for bi-xenon headlight flickering.

Illustration for editorial purposes

OEM Part Numbers

Accuracy note: we weren't able to verify a confident Audi A4 fog lights part number at the time of writing. Please confirm the correct part via an Audi dealer or parts specialist using your VIN.

Rarely Used, Easy to Forget About Until Needed

Fog lights sit unused for most owners most of the year, which means a fault can go unnoticed for a long time — right up until a genuinely foggy morning makes the problem obvious at the worst possible moment.

Before you buy: fog light fitment and bulb type vary by trim — not every trim level includes them as standard. Always confirm against your VIN before ordering.

What It Does

Front fog lights are angled and positioned to illuminate the road surface in low visibility conditions without creating the glare a standard headlight beam would in fog. Some higher trims of the A4 integrate fog lights into the same housing as cornering lights or daytime running lights, which affects both the part number and the complexity of any repair.

Fitment & Compatibility

Not every trim level of the A4 comes with fog lights fitted as standard, and the housing design often differs between trims that have them integrated with other lighting functions and those with a standalone unit. Always confirm your specific trim's fitment before ordering. Whether you're sourcing a replacement fog lights for your Audi A4 from a dealer, specialist, or online marketplace, always check compatibility against your registration or VIN before buying, and confirm you're ordering the correct side — driver's side (RH in the UK) or passenger side (LH in the UK) — since these are not interchangeable.

Common Faults

What to Look For

One side not working — usually a blown bulb, the most common and easiest fault to fix.
Neither side working — more likely a blown fuse or a faulty switch than two bulbs failing simultaneously.
Condensation inside the lens — points to a failed seal, worth addressing before it affects the bulb or wiring.
Cracked housing from front-end impact — common given their low mounting position, usually a straightforward like-for-like replacement.

DIY Replacement Difficulty

Bulb replacement is usually an easy DIY job, though access varies — some versions require reaching up from underneath via the wheel arch liner, others come apart from the front. Full housing replacement is similarly straightforward on most versions. Expect 15–30 minutes for a bulb swap, longer if the housing itself needs replacing.

A Genuinely Alarming, Real Finding Worth Knowing

If multiple lights fail together, this is genuinely worth knowing: documented cases describe several lights going out around the same time being traced to a genuinely faulty fuse box, with individual fuses found melted inside it. It's also genuinely worth knowing a confirmed technical service bulletin exists covering certain models fitted with bi-xenon headlights, describing a xenon light sporadically flickering before going out, or failing permanently.

A genuinely useful clarification worth knowing about shared fuses: reverse lights, rear fog lights, and the number plate light can share a single, common fuse on some models — worth checking this specific fuse first if several fail together.

It's also genuinely worth knowing that a complete lack of power to the front fog lights has, in documented cases, simply been down to dirty contacts or a relay not fully seated in its socket, rather than a genuine component failure.

OEM vs. Aftermarket

Reputable aftermarket fog light units and bulbs are a reliable, cost-effective alternative to OEM parts for the vast majority of cases, since this is a relatively simple lighting component without the complexity of adaptive or LED headlight systems.

More Audi Fog Lights Guides

The same part, covered across other Audi models.