What does the AC on Audi's air conditioning mean?

[MacBrielle]

It refers to the daytime running lights. The function of daytime running lights is to make the vehicle more easily recognizable during daytime driving. Their purpose is not to help the driver see the road better, but to let others know that a vehicle is approaching. Therefore, these lights are not illumination lights but signal lights. The primary benefit of daytime running lights is not aesthetic but to enhance the vehicle's visibility. More related information is as follows: Light distribution performance of LED daytime running lights: The most crucial aspect of LED daytime running lights is their light distribution performance. Daytime running lights must meet basic brightness requirements but should not be too bright to avoid disturbing others. In technical terms, the luminous intensity on the reference axis should not be less than 400cd, and the luminous intensity in other directions should not be less than the product of 400cd and the percentage of the corresponding point in the light distribution diagram. In any direction, the light intensity emitted by the lights should not exceed 800cd.