Humidity Sensor In Fresh Air Intake Duct -G657- FUNCTION

WARNING: This page is about a different variant/trim than selected.

NOTE:

The Air Quality Sensor -G238- and the Humidity Sensor in Fresh Air Intake Duct -G657- are only installed on a "Convenience" A/C system version (on an automatic climate control system).

For vehicles with a "Basic" A/C system version, neither an Air Quality Sensor -G238- nor a Humidity Sensor In Fresh Air Intake Duct -G657- is installed.

In addition to the Humidity Sensor In Fresh Air Intake Duct -G657- -1-, an Air Quality Sensor -G238- -3- is integrated in the housing -2- on a "Convenience" A/C system version (on an automatic climate control system).

Courtesy of AUDI OF AMERICA, LLC

There are different versions of the Air Quality Sensor -G238- -3- and the Humidity Sensor In Fresh Air Intake Duct -G657- -1-. Pay attention to the correct allocation.

The Humidity Sensor In The Fresh Air Intake Duct -G657- 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 The Fresh Air Intake Duct -G657- can be severely affected by direct contact with water so that correct moisture values can no longer be determined (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.
The Humidity Sensor In Fresh Air Intake Duct -G657- calculates the temperature and the moisture in the air flowing by and exchanges the information with the Climatronic Control Module -J255-.
The measured value of the Humidity Sensor In Fresh Air Intake Duct -G657- is evaluated by the Climatronic Control Module -J255-. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.

NOTE:

Certain A/C system functions (for example, the regulation of the "automatic recirculating air mode") can be switched on and off via the Multimedia System Control Head -E380-. These settings appear in the instrument cluster center display. Therefore, first check the preset for the "automatic recirculating air mode" if there is a complaint. Refer to the Owner's Manual.

The Climatronic Control Module -J255- calculates the current, relative humidity of the drawn-in fresh air from the measured values and the moisture in the vehicle interior from the measured values of the Humidity Sensor -G355- (installed in the mirror base. Refer to Humidity Sensor -G355-, REMOVING AND INSTALLING . 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 -J255- changes various characteristic curves to counteract this. This can occur, for example, by lowering the evaporator temperature (by activating the A/C compressor), by raising the response thresholds for the request for "automatic recirculating air mode", by preventing engine shut-off via the Start/Stop function, etc.

NOTE:

Check the Humidity Sensor In Fresh Air Intake Duct -G657- using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function. Refer to the appropriate Wiring Diagram.