Audi A4 Tail Lights: Specs, Fitment & Common Faults
A genuinely honest finding: identical cars parked side by side showed completely different condensation patterns, more noticeable after driving in the rain — plus an account of a dealer replacing the whole cluster with no questions asked.
Illustration for editorial purposes
OEM Part Numbers
More Wiring Behind There Than Most People Assume
A tail light unit typically bundles several functions into one housing — brake light, indicator, reversing light and rear fog light — which means a single electrical fault can affect more than one function at once, and a "faulty tail light" can mean several genuinely different things.
What It Does
Beyond basic rear visibility, tail light units on the A4 typically integrate brake lights, indicators, reversing lights and rear fog lights into a single housing. Higher trims may use LED units with a distinct light signature, which are not interchangeable with standard halogen units even if the physical mounting looks similar.
Fitment & Compatibility
Tail light design changed between generations of the A4, and facelifted versions within the same generation often use a revised light signature that isn't interchangeable with pre-facelift units. Always confirm the exact part for your specific model year before ordering. Whether you're sourcing a replacement tail 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 function out but others working — often a single blown bulb rather than a wiring fault, since multiple bulbs typically share one housing.
- Condensation inside the lens — points to a failed seal, which can damage electrics if left untreated.
- Flickering brake light — can indicate a failing bulb holder or a wiring connection issue.
- Cracked lens from impact — usually straightforward to replace like-for-like, though LED units cost considerably more than halogen equivalents.
DIY Replacement Difficulty
Bulb replacement is usually an easy DIY job, typically accessed from inside the boot without needing tools. Full unit replacement is slightly more involved but still manageable at home on most versions, generally requiring removal of a few boot trim fasteners. Expect 10–20 minutes for a bulb swap, or up to 45 minutes for a full unit.
A Genuinely Honest, Real Finding Worth Knowing
If a dealer suggests condensation in a tail light is simply normal, this is genuinely worth knowing: documented cases describe owners comparing otherwise identical cars parked side by side, finding some show condensation while others genuinely don't — worth knowing this isn't necessarily a universal design characteristic, and worth pushing for a proper repair rather than accepting a blanket "that's just how they are" explanation. It's also worth knowing this specific issue has been documented on more than one model in the range, more noticeably after driving for a while in the rain.
It's also genuinely worth knowing two distinct causes worth checking separately: the rubber seal between the cluster and the bulb holder should run centred and straight all the way around, and separately worth inspecting the cluster itself for hairline cracks. In at least one documented case, the actual cause turned out to be neither of these, but the light unit itself physically starting to separate at a seam over time.
OEM vs. Aftermarket
For basic halogen units, reputable aftermarket tail lights are a reliable, cheaper alternative to OEM. For LED units with a distinctive light signature, OEM or high-quality aftermarket replicas are worth the extra cost to avoid a mismatched look between the two rear light clusters.
More Audi Tail Lights Guides
The same part, covered across other Audi models.