Humidity Sensor In Fresh Air Intake Duct (G657)

Humidity Sensor In Fresh Air Intake Duct (G657)

• The Air quality sensor (G238) /Humidity sensor in fresh air intake duct is available in different versions. In this vehicle, a sensor - A - is installed in which the Air quality sensor - C - and the Humidity sensor in fresh air intake duct - D - are combined in a single component. Refer to the Electronic Parts Catalog.

• The Humidity sensor in fresh air intake duct installed in sensor - A - determines - D - the temperature and the moisture in the air flowing by. The Air quality sensor/Humidity sensor in fresh air intake duct installed in this vehicle exchanges information with the vehicle electrical system control module (J519) via the data bus. Therefore, ensure the proper version of the Air quality sensor/Humidity sensor in fresh air intake duct. Refer to the Electronic Parts Catalog.






• The measured value of the Humidity sensor in fresh air intake duct is evaluated by the vehicle electrical system control module and is transmitted via the data bus to the Climatronic control module (J255).

• Certain A/C system functions (for example control of automatic recirculation mode) can be switched on and off via the MMI (Multi Media Interface) under the "A/C system" function in the "car"/"car systems" menu. The A/C system control can also be influenced via presettings in the MMI (Multi Media Interface) under the "A/C system" function in the "car"/"car systems" menu. Therefore, first check the presetting in the MMI in the case of a problem with these components. Refer to Infotainment/MMI operating instructions.

• The Climatronic control module uses the measured values to calculate the current relative humidity of the drawn-in fresh air. The calculated humidity value is used to detect whether there is a risk of the windshield, rear window, and door windows fogging up on the inside. If that is the case, the Climatronic control module changes various characteristic curves to counteract this. This can be performed, for example, by lowering the evaporator temperature (by activating the A/C compressor), by raising the response thresholds for the request for automatic recirculation mode, by preventing motor shut-off via the start-stop function, etc. Check using Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

• The Humidity sensor in fresh air intake duct needs about 2 minutes to reach its operating temperature after the ignition is switched on. During the warm-up phase, the function of the Humidity sensor in fresh air intake duct is limited.

• Sensor - A - (combination sensor with the humidity sensor in fresh air intake duct and the humidity sensor in fresh air intake duct) is a highly sensitive electronic component that can be damaged if it comes in direct contact with fluids, solvents, fuels and certain chemical compounds. The function of the humidity sensor in fresh air intake duct can be severely affected by direct contact with water so that correct moisture values can no longer be measured (briefly or permanently depending on the composition of the fluid). For this reason, do not install sensors that may have come into contact with these substances.