Tuesday, June 16, 2020

Technical Service Bulletin # Mercedes Benz Truck GL 550 LI82-10_P-050139 Date: 100818

Technical Service Bulletin # Mercedes Benz Truck GL 550 LI82-10_P-050139 Date: 100818

Lighting - Headlamps/Front Fog Lamps Leaking Or Fogged

Headlamps/front fog lamps leaking or fogged

Topic number LI82.10-P-050139

Version 1

Design group 82.10 Exterior lights

Date 08-18-2010

Validity All vehicles

Reason for change Remedy revised and the new model series incorporated / Supersedes DTB T-B-82.10/334


Headlamps/front fog lamps leaking or fogged


As the headlamp is cooling down, e.g. after switching off, in rain or when washed, air is drawn in and the moisture from the air condenses on the

headlamp lens.

The ventilation of the headlamps ensures that this condensation is dissipated again after a short period of operation.

If the customer complains about fogging that is not present at the time of the workshop visit, then this is condensation. For these reasons,

condensation is a natural phenomenon and does not indicate a defect or malfunction; warranty and goodwill claims with this complaint will be



Remedy 1:

A defective headlamp can be identified as follows:

1. Check headlamps for external damage and also check for correct seating/locking of the caps.

2. If the headlamp exhibits external damage:

3. Remove/install/replace headlamp.

4. Check headlamp setting and correct if necessary.


If there is external damage on the headlamp or if the caps are not correctly seated/locked, there is no grounds for a warranty or goodwill


Remedy 2:

Clearing fogged/condensed headlamps:

1. Drive the vehicle into the workshop and connect the exhaust extractor.


In dry weather (temperature higher than +15掳C/+59掳F), you can also treat the vehicle out of doors.

Do not perform an engine wash before the defogging test.

2. Start the engine and switch on the following lights:

a. Main headlamps and front fog lamps fogged: High and low beams, front fog lamps, hazard warning system.

b. Only front fog lamps fogged: Front fog lamps.

3. Leave the vehicle in this state for 40 minutes.

2011 Mercedes Benz Truck GL 550 (164.886) V8-5.5L (273.963) Page 81

4. Switch off all lights and the engine.

5. Check the fogging; a noticeable reduction in the amount of fogging must be visible (progress of defogging process).


If no reduction in the degree of fogging is visible, the headlamp is defective and must be replaced.

It is not physically possible to defog the headlamps completely.

Fogging does not impair the operation or the service life of the headlamp.