This shows the outside temp sensor that reports the temperature to the digital dash.

When it shows -40C, the sensor is dead or a wire/plug is loose. The sensor value is thought to be 3.6k

928 613 241 00 Schalter 65,90 €
928 555 463 02 Gewindebuchse 6,28 €
928 613 082 00 Knopf 5,83 €
928 613 240 00 Umschalter 56,30 €