Proper Application Of Chip Protection Films (VERSION 1)

Publication date: 2024-09-09
Reference number: VERSION 1
Supersedes refnos: LI98.00-P-078106

HEADLAMPS OR FRONT FOG LAMPS LEAKING OR FOGGED

TECHNICAL SERVICE BULLETIN

Reference Number(s): LI82.10-P-078301 Version 2, Date of Issue: April 28, 2025

MERCEDES-BENZ:	All vehicles
FUNCTION GROUP:	82.10 - Exterior lights
REASON FOR CHANGE:	Change of reference to GI

COMPLAINT

Headlamp, front fog lamp leaky or fogged

ATTACHMENTS

File	Description
Scheinwerfer.docx	Rectify this fogging problem using Remedy 1
Defekte Scheinwerfer.docx	Replace the headlamps for this complaint

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:

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.
Switch off the engine and connect battery support via a charger.
Open the hood or trunk.
Switch on the lights.
Leave the vehicle in this state for 60 minutes.
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:

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.
Switch off the engine.
Open the hood.
Switch off the lights.
Leave the vehicle in this state for 60 minutes.
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:

Check the headlamp for external damage and that the cover caps and the diaphragm are correctly seated.
Check the electrical connectors of the plugs and pins.
Check for leak tightness in accordance with LI82.10-P-078896 HEADLAMP LEAK TEST. The test can only be conducted on headlamps.
If the headlamp or the rear lamp has any external damage, replace the component part in accordance with the WIS instructions.

NOTE: External damage to the headlamp/rear lamp or faulty seating of the cover caps does not present a warranty or goodwill case.

With headlamps, it is possible to install desiccant packs if the problem occurs repeatedly.

Open ventilation system LI82.10-P-078302 FOGGED HEADLAMP WITH DESICCANT PACK INSTALLED - OPEN VENTILATION SYSTEM

Closed ventilation system LI82.10-P-078304 FOGGED HEADLAMP WITH DESICCANT PACK INSTALLED - CLOSED VENTILATION SYSTEM

Disclaimer

NOTE: The information contained in this document is intended for use by trained, professional technicians with the knowledge to properly and safely perform diagnosis and repairs on Mercedes-Benz vehicles, using Mercedes-Benz approved tools and equipment. It informs service technicians about conditions that could occur in certain vehicles and provides information that could assist in proper vehicle diagnosis, service, or repair. It does not indicate that a defect is present in any vehicle referenced in this document nor does it imply warranty coverage. DO NOT assume that a symptom or condition, or a described cause of a symptom or condition, affects any particular vehicle or groups of vehicles, or that a described repair applies to any particular vehicle or groups of vehicles. There can be multiple causes resulting in the same or similar symptoms or conditions described in this document, and trained professional service technicians must use their diagnostic skills to make evaluations on a case-by-case basis. The information contained in this document does not guarantee warranty coverage nor does it extend the vehicle's warranty in any way.

SYMPTOMS

Lighting > Exterior lights > Front fog lights > Malfunction

Lighting > Exterior lights > Driving lights > Main headlamps > Fogged

Lighting > Exterior lights > Driving lights > Taillamp > Fogged

OPERATION NUMBERS/DAMAGE CODES

Op. no.

Operation text

Time

Damage code

Note