If the air cond filter in a Volkswagen car is not replaced when needed, it can cause several problems. The system may not be able to cool the cabin properly and it can cause a build-up of condensation and moisture inside the cabin, leading to a musty smell in the car. Additionally, mold and mildew can build up in the system, increasing the risk of breathing in unhealthy air. This can lead to respiratory infections, allergies and asthma attacks. And because the air circulation is not operating as it should, it can cause an unpleasant odor in the car, as well as excessive dust being circulated. Finally, the air cond filter plays an integral part in the overall engine performance, and if the filter is clogged or dirty, it can lead to the engine running at a lower performance, shorter life expectancy, and higher fuel consumption.