Filter device with a heater and a water sensor

The device has a filter element (32) arranged in a filter housing (28). A heater is provided for heating up medium flowing through the filter element, and a water sensor (50) is provided for detecting water collected in the filter housing. The heater is designed together with a water sensor as a structural unit. A central control device (16) is arranged in the filter housing for controlling a structural unit and heating performance of the heater and evaluating water level in the water sensor. An independent claim is also included for a method for operating a filter device.