Audi A4 Cabin Air Filter: Intervals, Fitment & Warning Signs

On the A4, most Audis genuinely have the filter behind the glovebox, but a few models place it under the windscreen cowl instead.

Illustration for editorial purposes

OEM Part Numbers

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

Easy to Forget, Easy to Fix

Unlike most parts covered here, this one has no bearing on how the car drives or performs — its only job is air quality inside the cabin, which makes it very easy to forget about entirely until something forces the issue.

Before you buy: filter size and whether your car uses a standard or activated-carbon filter varies by trim. Always confirm against your VIN before ordering.

What It Does

The cabin air filter cleans incoming air before it reaches the car's ventilation system, trapping dust, pollen and, on activated-carbon versions, some airborne odours and pollutants. It has no connection to the engine air filter, which is a completely separate part serving the combustion process rather than the cabin.

Fitment & Compatibility

Filter size and type are usually consistent within a generation of the A4, though higher trims sometimes fit an upgraded activated-carbon version as standard. Always confirm which type is fitted to your specific trim before ordering a replacement. Whether you're sourcing a replacement cabin air filter for your Audi A4 from a dealer, specialist, or online marketplace, always check compatibility against your registration or VIN before buying.

Warning Signs & Replacement Interval

Symptoms Worth Acting On

Musty or stale smell from the vents — one of the clearest signs a filter is overdue for replacement.
Reduced airflow from the vents — a clogged filter restricts air volume even at maximum fan speed.
Increased fan noise at the same setting — the fan working harder to push air through a blocked filter.
Visible dust or debris around the vents — can indicate the filter is no longer trapping particles effectively.

Most manufacturers recommend replacement every 12,000-15,000 miles or annually, though this can shift shorter if you regularly drive in dusty or polluted conditions.

DIY Replacement Difficulty

This is one of the easiest DIY jobs on the entire car — most versions are accessed either behind the glovebox or under the bonnet, requiring no tools beyond opening a simple access panel. Expect 5-15 minutes for most vehicles.

A Genuinely Important Clarification Worth Confirming Before Buying a Filter

This is genuinely worth confirming before ordering a replacement: most Audis use a front-access method with the filter positioned behind the glovebox, but a small number of models instead place the filter under the cowl at the base of the windscreen — worth confirming which specific location applies to your car before buying, since the part and fitting procedure are completely different between the two.

A genuinely useful, preventative finding worth knowing: consistently using the recirculation setting rather than fresh air mode helps keep the evaporator dry, which can prevent musty smells and mould developing in the first place. It's also genuinely worth knowing a useful technique for an existing smell: setting the heater to high with recirculation on and letting the car idle for around fifteen minutes can help bake an existing smell out of the evaporator.

It's also genuinely worth knowing to check the plenum area below the windscreen for a build-up of leaves and debris, since this is a regularly documented source of water finding its way into the cabin.

OEM vs. Aftermarket

Reputable aftermarket cabin air filters are widely regarded as fully equivalent to OEM parts, and this is genuinely one of the least risky parts on this site to buy on price alone rather than brand name.

More Audi Cabin Air Filter Guides

The same part, covered across other Audi models.