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April 28, 2025 Service bulletin

Complaint Headlamp, front fog lamp leaky or fogged Cause Fogging of the headlamps is a natural phenomenon,...

Mercedes-Benz technical service bulletin LI82.10-P-078301 for 2010-2025 Mercedes-Benz C300, 2003-2017, 2020-2025 Mercedes-Benz E350 and 2008-2009 Mercedes Benz C300 and others.

Bulletin number
LI82.10-P-078301
Component
Exterior lighting
Summary
Complaint Headlamp, front fog lamp leaky or fogged Cause Fogging of the headlamps is a natural phenomenon, which can occur under certain climatic conditions. It does not lead to any technical impairment of the headlamp. Remedy NOTE: If a pressure compensation diaphragm is fitted in the housing cover, then the lamp unit is a "closed system". Headlamp: Remedy 1 Clearing fogged/condensed LED headlamps and LED rear lamps: 1. Drive vehicle into workshop (temperature higher than +18 °C/+64.4 °F) and connect the exhaust extraction. Note: Do not perform an engine wash before the defogging test. 2. Switch off the engine and connect battery support via a charger. 3. Open the hood or trunk. 4. Switch on the lights. 5. Leave the vehicle in this state for 60 minutes. 6. Check for formation of condensation, a significant reduction in the formation of condensation must be clearly recognizable (thawing progress). Clearing fogged/condensed halogen/xenon headlamps: 1. Drive the vehicle into the workshop (temperature higher than +18 °C/+64.4°F). Note: Do not perform an engine wash before the defogging test. 2. Switch off the engine. 3. Open the hood. 4. Switch off the lights. 5. Leave the vehicle in this state for 60 minutes. 6. Check for formation of condensation, a significant reduction in the formation of condensation must be clearly recognizable (thawing progress). Note: If there is no visible reduction in the formation of condensation, check the headlamp for damage. (See Remedy 2) It is not physically possible to defog the headlamps completely. Fogging does not impair the operation or the service life of the headlamp. Remedy 2 A damaged headlamp can be identified as follows: 1. Check the headlamp for external damage and that the cover caps and the diaphragm are correctly seated. 2. Check the electrical connectors of the plugs and pins. 3. Check for leak tightness in accordance with LI82.10-P-078896 The test can only be conducted on headlamps. 4. If the headlamp or the rear lamp has any external damage, replace the component part in accordance with the WIS instructions.

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