The automatic transmission has a temp sensor that signals when the transmission oil gets 95C. It is actually a switch, an on/off type. It makes contact at 95C.

By making contact, the fan controller box next to the seat of a S4/GT/GTS is activated (even without the key in the ignition lock) to run the fans at moderate speed. This is what is sometimes called "after cooling" and simply prevents temperatures rising even further causing oil to burn.

Below you see both sensors, the upper one is the temp sensor, linked to the oil feed from the cooler (front) into the transmission housing, and the one below is the  transmission protect switch which signals the EZK that the transmission is shifting gear and the EZK should retard a few degrees to reduce torque, and avoid slipping of the friction parts inside the transmission.