Headlamps/front fog lamps leaking or fogged
Topic number

LI82.10-P-078301

Version

4

Function group

82.10 - Exterior lights

Date

3/9/26

Validity

All cars except G-Class before model year 2018

Reason for change

Model series added

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.
If a pressure compensation diaphragm is fitted in the housing cover, then the lamp unit is a "closed system".

Remedy
Headlamp:
Remedy 1
Clearing fogged/condensed LED headlamps:
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.
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).
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© Copyright Mercedes-Benz AG

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Clearing of fogged/condensed LED headlamps and LED rear lamps on electric vehicles:
1. Drive the vehicle into the workshop (temperature higher than +18 °C/+64.4°F).
2. Connect battery backup via a charger.
3. Open the front-end flap and ensure sufficient ventilation.
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 condensation, check the headlamp for malfunctions. (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.
Note: Only implement Remedy 1 for model series 463 (from model year 2018) and model series 465.
Remedy 2
A defective 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 according to LI82.10-P-078307. 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.
Note:
External damage to the headlamp/rear lamp or faulty seating of the cover caps does not present a warranty or goodwill case.
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© Copyright Mercedes-Benz AG

SAHARRY

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Note:
With headlamps, it is possible to install desiccant packs if the problem occurs repeatedly.
• Open ventilation system LI82.10-P-078302
• Closed ventilation system LI82.10-P-078304

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

09.03.2026 14:55
© Copyright Mercedes-Benz AG

Time

SAHARRY

Damage
code

Note

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