Adjusting and replacing LED headlights

Here you can find useful information and valuable tips on all aspects of replacing and adjusting an LED headlight on a Mercedes-Benz W212.

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.

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.

System components


1. Plastic lens
2. Lens holder
3. 2*6 chip LED light source
4. Vario roller with IHC+ functionality
5. CIPOS sensor system for the roller position


The 2*6 chip LED module/range module generates a luminous flux of up to 2765 lm, whereby the road illumination optimally supports the driver with all the various light distributions.


1. Lens / reflector lens holder
2. Carrier frame
3. Harness assembly
4. Thermal sensor
5. Contact element+LED
6. Heat sink


The 5 chip road surface module generates a luminous flux of up to 1260 lm, which achieves homogeneous illumination in the "near field" range.


LED DI; light guide carrier with 8 LEDs and primary optics.


LED-DRL-PO light distribution, light guide technology.


Bulb shield for targeted illumination of the cornering area.


The light control units control various functions, such as lighting functions, SW fan/thermal management, Vario LED module functions, etc.


In addition, the control units - together with the vehicle system - regulate light distributions for the driving situation via the CAN bus using the Vario LED module.

  • (Roller) adaptive light actuator
  • (Height adjustment) vertical light actuator
  • (Dynamic cornering light / swivel function) curve light actuator


As is the case with other electronic components, the powerful LEDs with their enormous light output  from a comparatively small chip surface must be operated within certain temperature limits. To this end robust fans specially designed for headlamp technology are integrated in an intelligent thermal management system.

Defective LED headlight: Symptoms

The following effects can occur if LED headlamps fail:

  • Fault lamp lights up (system-dependent)
  • Fault entry in the relevant headlamp control unit

LED headlight defective - the causes: Causes of failure

The following causes may be responsible for failure or malfunction:

  • Power supply faulty
  • External damage; accident
  • Vehicle system, CAN bus values implausible
  • Failure of headlamp electronics
  • Defective control unit
  • Defective headlamp fan

Checking LED headlight: Troubleshooting

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. 

Control unit diagnostics

As part of control unit diagnostics, it is possible to employ the help of various functions and vehicle information as and when needed.

Fault code  
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).


Actuator test 
In this function, vehicle-specific headlamp functions can be controlled separately (Fig. 3).

Adjusting LED headlight: Instructions

Preparation for headlamp adjustment

Before the headlamps can be adjusted, the following work must be carried out on the vehicle: 

  • Check tyre pressure and correct if necessary.
  • Check load.
  • Ensure correctly calibrated vehicle level; for vehicles that were previously raised, roll/drive them a few metres before adjustment so that the chassis "springs in".
  • Put the steering wheel in "straight ahead" position.
  • Close all doors.
  • Read off the vehicle-specific forward inclination, in this case 1%.
  • Align the beamsetter in front of the vehicle, i.e. the headlamp.

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.

Adjust the headlamp using the beamsetter

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.

Carry out the following steps on the diagnostic unit/vehicle

Connect a diagnostic unit and then align a beamsetter in front of the vehicle.

  • Select vehicle
  • Switch on the ignition
  • Read out and clear error memory
  • Select basic setting "Adjust headlamp" 
  • Select zero setting 
  • Switch on headlamps
  • Confirm zero setting. This sets the headlamps to the basic setting "Adjust headlamp". 
  • Carry out headlamp adjustment, i.e. beam setting.

Set the dial and light pattern

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).

Confirm new values

After adjustment, confirm new values on the diagnostic unit.

  • Secure vehicle against automatic starting
  • Completely switch off the electrical system, remove the ignition key.
  • Dismantle wheels, inner mudguards, bumpers
  • Disconnect electrical connections
  • Remove the headlamps
  • !!! ESD - guard against this when handling electronic components.
  • Attach the control units to the new headlamps at a separate workstation. Make sure that the connectors are correctly locked and that the seals are seated correctly. Observe tightening torques!
  • Adjust the height of the fixing banjo bolts between the old/new headlamp. When assembling, this is helpful in order to comply with the body gap/bumper headlamps.
  • Adaptation: in some cases it may be necessary to adapt the LED headlamp to the vehicle after installation and before adjustment. To do this, a connection between the vehicle and the server of the vehicle manufacturer has to be set up. Connect the diagnostic unit or VCI unit to the server in accordance with the manufacturer's specifications and follow the instructions in the vehicle manufacturer's application.

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.

Changing LED headlight on the Mercedes-Benz W212: VIDEO

Replacement of a full LED headlamp on the Mercedes-Benz W212

In this video we show you how to professionally replace a full LED headlamp on a Mercedes-Benz W212 (model year 2014).