The full LED headlamp
Here you can find useful information and valuable tips on all aspects of replacing and adjusting an LED headlight on a Mercedes-Benz W212.
Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only.
Requirements for vehicle lighting are steadily increasing, a fact which places high demands on vehicle lighting systems. LED headlamps with innovative lighting functions are integrated into the systems of modern vehicle models. The functions are monitored by higher-level control units. Even a seemingly simple replacement of a headlamp requires special work steps in order to carry out a professional diagnosis and repair.
The following information including service work shown is based on the example of a Mercedes Benz W212 (model year 2014) but also applies to other vehicle models with identical component systems.
The following effects can occur if LED headlamps fail:
The following causes may be responsible for failure or malfunction:
The LED headlamps or rather the vehicle lighting is monitored by higher-level control units. Any occurring errors are stored in the control unit's error memory and can be read using a suitable diagnostic unit.
With some vehicle models, a warning message can also be displayed on the instrument cluster in the event of a system error. However, before control unit diagnostics are undertaken, it is first of all advisable to carry out a visual check on the individual system components as part of initial troubleshooting activities.
As part of control unit diagnostics, it is possible to employ the help of various functions and vehicle information as and when needed.
In this function, the fault codes stored in the error memory can be read. For subsequent troubleshooting, the error code description contains general information on possible effects or causes (Fig. 1).
In this function, current measured values from the control unit can be selected and displayed for the various lighting functions (Fig. 2).
In this function, vehicle-specific headlamp functions can be controlled separately (Fig. 3).
Before the headlamps can be adjusted, the following work must be carried out on the vehicle:
The vehicle and the beamsetter must stand on level ground (with the headlamp setting position in accordance with country-specific requirements).
It is recommended to connect a suitable battery charger to support the vehicle electrical system.
The various diagnostic options are illustrated using the mega macs 77 diagnostic unit as an example. The respective test depth and variety of functions can be set out differently depending on the vehicle manufacturer and is dependent on the relevant system configuration of the control unit.
Connect a diagnostic unit and then align a beamsetter in front of the vehicle.
Set the dial of the analogue beamsetter to 1%. Mechanically adjust the light pattern in the horizontal position to the (reference line of height adjustment) or the vertical cut-off line to the O° line (Fig. 4).
With the digital beamsetter, use the proven vehicle and headlamp system selection. Select the inclination 1%. Then use the digital guide lines to mechanically adjust the light pattern correctly (Fig. 5).
After adjustment, confirm new values on the diagnostic unit.
Repair work on the lighting system in a vehicle may only be carried out by trained specialists. Repair work that is carried out incorrectly can lead to system failure and to severe personal injuries. For all repair work performed on the lighting system, please observe the safety and assembly instructions relating to the system in question and/or to those instructions provided by the relevant vehicle manufacturer.