2021 Mercedes-Benz AMG GT Headlamp Fogging TSB

Owners of the 2021 Mercedes-Benz AMG GT may notice headlamp and fog lamp fogging. This manufacturer communication, TSB L182.10-P-078301, addresses this common complaint and outlines the diagnostic and repair procedures for technicians.

Symptoms

This technical service bulletin covers the following owner-facing symptoms related to exterior lighting:

• "Headlamp, front fog lamp leaky or fogged"
• "Lighting > Exterior lights > Front fog lights > Malfunction"
• "Lighting > Exterior lights > Driving lights > Main headlamps > Fogged"
• "Lighting > Exterior lights > Driving lights > Taillamp > Fogged"

Cause of Headlamp Fogging

Mercedes-Benz states that fogging of the headlamps is a natural phenomenon. This can occur under certain climatic conditions and does not inherently lead to any technical impairment of the headlamp.

If a pressure compensation diaphragm is fitted in the housing cover, the lamp unit is considered a "closed system." Condensation can still form within such systems due to temperature and humidity changes.

Important Warnings for Owners

Owners should be aware of specific conditions and limitations regarding headlamp fogging:

• Do not perform an engine wash before any defogging test, as this can interfere with the diagnostic process.
• It is not physically possible to defog the headlamps completely. Some residual fogging may remain.
• Fogging, when natural, does not impair the operation or the service life of the headlamp.
• External damage to the headlamp or rear lamp, or faulty seating of the cover caps, does not present a warranty or goodwill case. This means repairs for such issues would likely be at the owner's expense.

Repair Procedure Summary

Technicians follow a specific procedure (Remedy 1) to clear fogged or condensed headlamps, front fog lamps, and rear lamps. This process is similar for LED, electric vehicle LED, and halogen/xenon headlamps.

1. The vehicle is driven into a workshop where the temperature is higher than +18 °C (64.4 °F). Exhaust extraction equipment is connected.
2. The engine is switched off, and battery support is connected via a charger.
3. The hood is opened to allow ventilation. For electric vehicles, the front-end flap is opened to ensure sufficient ventilation.
4. The vehicle's lights are switched on.
5. The vehicle is left in this state for 60 minutes.
6. After 60 minutes, the technician checks for a significant reduction in condensation, indicating successful thawing progress.

Diagnosing Defective Headlamps (Remedy 2)

If the initial defogging procedure does not visibly reduce condensation, technicians proceed to identify a potentially defective headlamp. This involves several checks:

1. External Damage: Inspect the headlamp for any external damage and verify that the cover caps and diaphragm are correctly seated.
2. Electrical Connections: Check the electrical connectors, plugs, and pins for proper seating and condition.
3. Leak Tightness: A leak tightness test is performed according to a separate technical bulletin, LI82.10-P-078307. This test is specifically for headlamps.
4. Component Replacement: If external damage is found on the headlamp or rear lamp, the component part is replaced following the manufacturer's Workshop Information System (WIS) instructions.

If your 2021 Mercedes-Benz AMG GT headlamp fogging persists after the initial clearing attempt, further diagnosis is necessary to determine if a defect is present.

Related Technical Bulletins

For recurring headlamp fogging issues, technicians may consider installing desiccant packs. This process refers to additional technical bulletins:

• LI82.10-P-078302 for open ventilation systems.
• LI82.10-P-078304 for closed ventilation systems.

Source: NHTSA ID: 11029025