Mercedes-Benz bulletin LI82.10-P-078307

Complaint Headlamps leaking or fogged Cause The fogging of the headlamp is a natural phenomenon which can occur under certain climatic conditions. In contrast to a leaky headlamp, physical fogging does not result in a technical impairment of the headlamp. A leak test must be performed to determine if physical fogging exists or if the headlamp is leaky. Remedy In advance, observe LI82.10-P-078301 "Headlamp/front fog lamp leaky or fogged". 1. Prepare headlamp/check for external damage: For headlamps with a closed system • Check the headlamps for any external damage and check also for correct seating of the Gore-diaphragm/correct latching of the cover caps. • If the headlamp exhibits any external damage, replace the headlamp. For headlamps with an open system • Check the headlamps for any external damage and seal off the vent then make sure the cover caps are latched correctly into place. • If the headlamp exhibits any external damage, replace the headlamp. Note: A headlamp with external damage is not a warranty or goodwill case. 2. Leak test of headlamp with overpressure: Connect test adapter to pressure tester. (Figure 1) Check test adapter for leak tightness. To do so, connect plug and coupling (Figure 2) and apply a maximum overpressure of 30 mbar. • The pressure must remain constant. If the pressure does not remain constant, use a new adapter. Seal all the outlet openings using sealing compound and the given diaphragm with the plunger (Figure 3). (Figure 4) • Make allowance for the different headlamp variants here (there are different outlet openings). Check if the headlamp needs to be removed to gain access to the diagnostic socket on the headlamp housing. Plug the adapter onto the diagnostic socket on the headlamp housing. (Figure 5). Apply a maximum of 30 mbar overpressure to the headlamp housing. Note: If the maximum overpressure of 50 mbar is exceeded the headlamp seal will be damaged. • If a pressure drop of less than 10 mbar is measured within 30 seconds, the headlamp is tight and there is natural physical condensation• If a higher pressure drop than 10 mbar is measured within 30 seconds, the headlamp is leaky. Note: The leaky position can be localized with the aid of soap suds. Replace any leaky headlamps. Desiccant packs can be installed for headlamps that are not leaky. Observe the following documents for installation of desiccant packs: • LI82.1

Owners of the 144 model years this bulletin names have filed 4,461 complaints with NHTSA since 2015. 51 of them name Exterior Lighting — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.