How to Distinguish Between Internal and External Air Circulation in Passat?

[McMartin]

When the button light is off, it indicates the external air circulation is activated. In external circulation mode, the air conditioning draws air from outside the vehicle, while internal circulation reuses the air inside the car. Below are the relevant details: 1. Internal Circulation Mode: In this mode, outside air does not enter the car. The air only circulates within the vehicle. Therefore, activating the internal circulation mode prevents polluted or unpleasant outside air from entering the car. When the outside temperature is low, turning on the internal circulation mode can improve heating efficiency, as only the air inside the car is heated. 2. Principle: External circulation mode uses a fan to draw outside air into the car, meaning the air ducts between the inside and outside of the vehicle are open. The air blown by the fan comes from outside, and even if the fan is not turned on, airflow is still drawn into the car while driving, replenishing fresh air inside.