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 Number: 8K0819439

Accuracy note: this part is genuinely consistent across engine and trim variants, since it's part of the HVAC system rather than the drivetrain.

Cabin air filter, B8 generation	Audi OEM: 8K0819439 — also cross-referenced as 8K0819439C; shared with A5, allroad, Q5, RS5, S4, S5, SQ5

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.

Audi A4 Cabin Air Filter reference plate

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.

Warning Signs, DIY Difficulty & Aftermarket Advice

These are the same regardless of make or model — see our full Cabin Air Filter Guide for signs it needs changing, confirming fitment against your VIN, and choosing standard, carbon, or HEPA media.

More Audi Cabin Air Filter

The same part, covered across other Audi models.