What is the reason for the bulb indicator light in a Volkswagen car being on?

[VanJonathan]

Volkswagen car dashboard displaying a bulb icon indicates a lighting system malfunction. Below is expanded information on headlights not working: 1. Symptom: When the light switch is turned to position 2 or 3, the small lights and dashboard work normally, but both high and low beams of the headlights do not illuminate. 2. Possible causes: The main reasons for lights not working include bulb failure, fuse blowout, damage to the light switch or relay, and open or short circuits in the wiring. 3. Diagnosis: Turn the light switch to the headlight position and use a test light to check the "power" terminal of the dimmer switch. If the test light does not illuminate, check the corresponding terminal of the light switch with the test light; if the test light illuminates, it indicates an open circuit in the wire between the two switches; if the test light does not illuminate, the light switch is damaged. When checking the terminals of the dimmer switch, if the test light illuminates, the dimmer switch is damaged. Use wires to connect the "power" terminal of the dimmer switch to the high and low beam terminals respectively; at this point, both high and low beams should light up.