Fogged Headlamp With Desiccant Pack
Installed - Closed Ventilation System
Topic number

LI82.10-P-078304

Version

1

Function group

82.10 - Exterior lights

Date

9/9/24

Validity

Small service cover:
Model series 205 facelift with SA code: 631, 632
Model series X156 before facelift with SA code: 613, 620,
614, 615, 616, 618, 621, 622
Model series X156 facelift with SA code: 613, 620
Model series X166 facelift with SA code: 631, 632, 640,
641, 642
Model series W166 before facelift with SA code: 621, 622
Model series 172 facelift with SA code: 613, 620
2x small service covers:
Model series 205 facelift with SA code: 640, 641, 642
Model series 117 facelift with SA code: 613, 620
Model series X166 facelift with SA code: 613, 620
Model series 253 before facelift with SA code: 613, 620
Model series 206 as of 12.2022
Model series 214, all
Model series 236, all
Model series 243, all
Model series 296, all
Model series 247.9 GLA, all
Model series 223 as of 12.2021

Large service cover:
Model series 176 before facelift with SA code: 614, 615,
616, 618, 621, 622

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Model series 117 before facelift with SA code: 614, 615,
616, 618, 621, 622
Model series 257 with SA code: 631, 632, 640, 641, 642
Model series 207 facelift with SA code: 631, 632
Model series X166 before facelift with SA code: 613, 620,
614, 615, 616, 618, 621, 622
Model series 253 facelift with SA code: 631, 632, 640,
641, 642
Model series 231 before facelift with SA code: 614, 615,
616, 618, 621, 622
Model series 251 facelift with SA code: 613, 620, 614,
615, 616, 618, 621, 622
Model series 232 with SA code: 631, 632, 640, 641, 642
Model series 247.6 GLB, all
Reason for change

Complaint
Headlamps fogged or droplets forming.

Cause
Due to the housing cover with pressure compensation diaphragm, the headlamps are a "closed system".
This means that the headlamps are protected against acid gases, dirt and exhaust gas.
However, moisture can still enter from two sources.
Through absorption and desorption (the commonest cause) or through permeation.
Moisture is either absorbed by the plastic material and, when the light source is switched on, it is released from the
plastic by desorption, or the moisture penetrates through the plastic materials of the headlamp from outside (permeation).
This can lead to the formation of condensation on the lens of the headlamp. The headlamps comply with all applicable
US standards and regulations.

Remedy
Check headlamps for natural fogging or condensation as per LI82.10-P-078301.
If a reduction in the degree of fogging is visible, the desiccant packs can be used once the condensation has completely evaporated.
Note: Order service covers and desiccant packs based on the validity description.
1. Remove existing service cover with diaphragm (Picture_01 (1)).
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2. Insert desiccant packs (Picture_01 (2)) into new service covers with diaphragm and seal with protective grille and
bolt down (Picture_01 (3)).
Note: One desiccant pack is required for each small service cover, and two desiccant packs are required for each large service cover.
3. Stick the supplied diaphragm onto the new service cover and attach at the headlamp.
Note: The bonding surface must be clean and dry.
4. If the headlamp housing has an additional 2nd diaphragm, this must be covered over with masking tape.
Note: The bonding surface must be clean and dry.
To ensure that the desiccant pack (absorption) acts effectively, the headlamp has to be air-sealed.
Observe or check the following points for this:
1. Seals at the central connector must all be present and correctly fitted (Picture_02).
2. The new transparent diaphragm must be correctly bonded (Picture_03).
3. Check headlamp housing for any external damage.

Attachments
File

Description

Bild_01.jpg

1) Existing service cover 2) Desiccant pack 3) Screw connection

Bild_02.jpg

1) Missing seals in central connector 2) Incorrectly fitted
seals in central connector

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Bild_03.jpg

Bonding position of the transparent diaphragm

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 > Driving lights > Main headlamps > Fogged

Parts
Part number

ES1 ES2 Designation

Quantity Note

EPC

A0008260900

Small service cover

1

See validity description

X

A0008261000

Large service cover

1

See validity description

X

Desiccant pack (20g)

1

See validity description

X

Masking tape

0.1

Masking tape for the existing 2nd diaphragm (on headlamp housing)

X

A000826160012

11

A0008262000

Operation numbers/damage codes
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Op. no.

Operation text

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Time

CCUSHWA

Damage
code

Note

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