Summary
Polish when the opacity is superficial and external; replace the lens or the entire unit when the polycarbonate is cracked, deeply crazed, deformed, or deteriorated from the inside. Cleaning alone will not permanently restore a missing UV protective layer.
How to tell if the defect is external?
Wash the headlight and then observe it from several angles, with the lights off. A uniform, slightly rough yellow haze often comes from external oxidation. Persistent fog, internal marks, or a tarnished reflector indicate a sealing or internal problem.
When is polishing enough?
Progressive wet sanding followed by polishing can remove the oxidized layer. It is necessary to protect the adjacent bodywork and maintain a regular surface. The restoration must end with a compatible UV protection, otherwise yellowing will quickly return.
When should the lens be replaced?
A crack allows moisture to enter and compromises the optics. A network of deep cracks, thermal deformation, or broken fasteners also justify a replacement. Opening a glued headlight requires a precise method to avoid damaging the housing and to restore watertightness.
What checks should be done after repair?
Check for condensation, the operation of all lamps, and the beam adjustment. If your vehicle matches the indicated reference, examine our headlight lens for Audi A4 B8 before deciding between restoration and replacement.