Hot film mass air flow sensor function - GF07.07-P-4118-02C
WARNING: This page does not describe the selected car, but rather 42 other vehicles, including the 1999 Mercedes-Benz S600, 1999 Mercedes-Benz S500, 1999 Mercedes-Benz S420, 1999 Mercedes-Benz S320, and 1999 Mercedes-Benz CL600. However, it is still accessible from the selected car via links, so may be relevant.
The electronics in the hot film mass air flow sensor (B2/5) controls the temperature of the heating resistor (RH ) by means of a variable voltage so that its temperature is 160°C above the intake air temperature detected by the temperature resistor (RL ). The temperature of the heating resistor (RH ) is detected by the sensor resistor (RS ).
If a change in temperature occurs because of an increase or reduction in the air flow, the electronics (9/5) adjusts the voltage of the heating resistor (RH ) until the temperature difference is again achieved. This control voltage is used by the engine control module as a measure for the metered air mass.