Why are both left headlights of the Audi A6 not working?

[VanElle]

Audi A6 left headlights not working may be due to the instrument panel reporting a daytime running light fault, and there is water vapor inside the headlight. Fault Analysis: Removing the headlight requires dismantling the front bumper. After removing the headlight, water is found inside. The control box at the lower part of the headlight (gas discharge bulb control unit) is disassembled, revealing that the circuit board has been corroded by water. The control unit needs to be replaced, but since water ingress indicates a leak, the headlight housing must also be replaced. A computer scan reveals a fault code indicating that the left headlight plug has no power supply. It is necessary to check the left 30-power supply terminal. The fuse is located above the relay box on the driver's side footwell, a 30-amp fuse. Solution: Install a new headlight directly, clear the fault code. The daytime running lights and headlights will function normally, and the instrument panel fault will disappear, resolving the issue.