2021 Mercedes-Benz AMG GT Headlamp Fogging and Leaks TSB

Owners of 2021 Mercedes-Benz AMG GT vehicles may notice their headlamps appearing fogged or even leaking. Mercedes-Benz has released Technical Service Bulletin (TSB) LI82.10-P-078307 to provide guidance for technicians on how to diagnose and address these concerns. This TSB helps distinguish between natural physical fogging, which is common under certain climatic conditions, and actual leaks that indicate a technical impairment of the headlamp.

Symptoms

Owners might observe the following issues related to their vehicle's lighting system:

• "Headlamps leaking or fogged"
• "Lighting > Exterior lights > Front fog lights > Malfunction"
• "Lighting > Exterior lights > Driving lights > Main headlamps > Fogged"
• "Lighting > Exterior lights > Driving lights > Taillamp > Fogged"

These symptoms, particularly the Mercedes-Benz AMG GT headlamp fogging, prompt a diagnostic procedure to determine the root cause.

Diagnosis and Trigger Conditions

Before performing a leak test, technicians are instructed to observe TSB LI82.10-P-078301, which also addresses "Headlamps or Front Fog Lamps Leaking or Fogged." The primary diagnostic step involves a pressure test to identify if the headlamp is truly leaky or if the fogging is a natural phenomenon.

Repair Procedure Summary

The diagnostic and repair process for Mercedes-Benz AMG GT headlamp fogging or leaks involves several key steps:

1. Headlamp Preparation and External Damage Check:

   • For headlamps with a closed system, technicians must inspect for any external damage, ensure correct seating of the Gore-diaphragm, and proper latching of the cover caps. If external damage is found, the headlamp must be replaced.
   • For headlamps with an open system, external damage is also checked. Technicians must seal off the vent and ensure cover caps are correctly latched. Damaged headlamps are replaced.

2. Leak Test with Overpressure:

   • A specialized test adapter (part number W000589059100) is connected to a pressure tester (Figure 1). The adapter's leak tightness is verified by applying a maximum overpressure of 30 mbar after connecting the plug and coupling (Figure 2).
   • All outlet openings on the headlamp are sealed using sealing compound and a diaphragm with a plunger (Figures 3 and 4). Different headlamp variants may have different outlet openings.
   • The headlamp may need to be removed to access the diagnostic socket on its housing. The adapter is then plugged into this socket (Figure 5).
   • A maximum overpressure of 30 mbar is applied to the headlamp housing.

3. Evaluating Test Results:

   • If the pressure drops by less than 10 mbar within 30 seconds, the headlamp is considered not leaky, and the Mercedes-Benz AMG GT headlamp fogging is attributed to natural physical fogging.
   • If the pressure drops by more than 10 mbar within 30 seconds, the headlamp is leaky. The precise location of the leak can often be identified using soap suds. Leaky headlamps must be replaced.

Required Tools or Parts

To perform the diagnostic leak test, a specific tool is required:

• Test adapter: W000589059100

Additionally, sealing compound and a diaphragm with a plunger are necessary for sealing headlamp outlet openings during the test.

Important Warnings

Owners and technicians should be aware of the following critical information:

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