See also:

Activating HDC
Press the button; the LED above the button lights up. ...

General information
Danger of burns from hot engine Do not open the cooling system while the engine is hot; otherwise, escaping coolant may cause burns.◄ Suitable additives Only use suitable additives; other ...

Deactivating HDC
Press the button again; the LED goes out. HDC is automatically deactivated above approx. 37 mph/60 km/h. ...