WARNING: This page is about a different car, the 2024 Audi S6 and 2024 Audi A6 Quattro. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: A/C Refrigerant High Pressure Switch
Courtesy of AUDI OF AMERICA, LLC
Function:
Switches the radiator fan to the next higher level (approximately 16 bar (232.06 psi)) when the pressure in the refrigerant circuit increases.