The plug of the Audi A4L heating valve is replaced as follows:
Steps to turn on the heater in Audi A4:
1. Press the driving button of the Audi A4 brake pedal.
2. Press the one-button start button of the Audi A4 car.
3. The instrument of the Audi A4 car lights up and the vehicle starts.
4. Press the Audi A4 AUTO button to turn on the air conditioning system.
5. Turn the Audi A4 temperature adjustment knob to the red area on the right to turn on the heating system.