Many folks on this forum have lamented the fact that they skipped the LED headlight option when purchasing their 2015-2018 W205. I'm one of those folks. My wife picked the car out and I didn't get a good look at the front. Well, we got the halogens. While my wife doesn't care, I do. So before we even made it off the lot, I hatched a plan to retrofit the LED clusters. If you don't believe this is possible, see the photo below (Hint: There is something wrong about this):

http://www.endoimage.com/Mercedes/P1080378.JPG

Before I start, I want to clear up a few of things. First, going from halogens to Static LED's is not an easy swap. It involves buying a decent set of LED headlights, partially disassembling them, then rewiring them so they work with the halogen headlight wiring. So don't believe the write-ups that state all you need is a harness. In fact, I did this swap in such a way as to leave everything on the car untouched by only modifying the LED headlights. This way the car can be returned back to halogens, if need be, with little trouble. There is no intermediate harness either. The car's headlight plug is connected directly to the headlight assembly.

Secondly, this writeup is about transforming a US/Canadian spec 2015-2018 C300 to static LED headlights. Conversion to active headlights is not covered and would likely be unfeasible, short of reprogramming the car and swapping out a good bit of hardware.

Thirdly, my method for modifying the LED headlights is irreversible, meaning the LED headlights can't be returned to their original configuration. However, removing the lenses of the headlights is not required.

Lastly, this swap does not involve reprogramming the vehicle. The car will act as though nothing has changed.

Before embarking on this project, please read this entire how-to.

Functionality:

As this modification is for US market cars using US market Static LED headlights, the headlights will function with the following functions/limitations:

1. There is no auto-dimming functionality.
2. There is no blue light function when the vehicle is unlocked.
3. Day time running lights (DRLs) remain illuminated when the turn signal is activated. DRL's will not function independently from the side marker lights. In other words, if the headlight switch is in Auto, and the headlights are off, the DRLs will be off. To have the DRL's function in the daytime, the headlight switch has to either be in the Headlights On or Parking Lights On position. This was a necessary concession to avoid running extra wires under the hood of the vehicle.
4. All lights run at a fixed intensity.
5. There is no auto leveling feature. The vehicle has no level sensors and the headlight assemblies do not have a provision for auto-leveling. The US spec Static LED headlight assemblies are fixed with the exception of the low beams which can be aligned manually from under the hood.
6. DRL's are tied to side marker light functionality. The only change in functionality over the halogen or LED equipped cars is DRL operation during turn signal operation and DRL operation during daylight as described in item 3 above.
7. The vehicle will not sense headlight malfunctions or display any headlight errors after installation.
8. There are no modifications or additions to the vehicle's wiring. Even the most savvy Mercedes technician will not notice that the assemblies have been swapped. Only in the case of a headlight malfunction will a technician start to realize that something is amiss. This modification should be disclosed when selling the vehicle. It is highly recommended to retain the halogen assemblies if the car is to be returned to stock (re-sale or lease close-out).
9. Temper your expectation for the brightness of these LED headlights. Aimed properly, I would characterize the low beams as adequate, with good illumination off to the sides. But they are no better than the halogens. The LED high beams are slightly better than the halogen high beams. I don't know if this conversion performs any better or worse than the factory equipped LED cars. My method slightly over drives the low beams but likely slightly under drives the high beams. But unless Mercedes did something exotic like pulse with modulation of the LEDs at very high intensity (unlikely) I expect the performance to be close to identical. The Institute for Highway Safety rated both the LED and halogen headlights as poor. I tend to agree, but the LED's do look better.

Cost:
$400-$1000 in total depending on the cost of the LED headlights. Supplies other than the headlights runs about $200.

Required Tools:
Basic hand tools including metric Allen wrenches and sockets
Soldering iron
Heat gun
Digital Multi-Meter
Torx bits/screwdriver: T-8 and T-20
3/64 flat head jeweler's screwdriver

Recommended tools:
12 volt, 5 amp fixed or variable power supply
Reading glasses
Headlamp
Label Making Machine
Magnetic and mechanical bolt retrievers

Supplies:
Solder
1/16, 1/8 and 3/16 inch heat shrink
22 AWG stranded wire in black
18 AWG stranded wire in black
8 x 4-32 x 3/8" flat head screws and nuts
Heat sink compound (recommended)

Components:
4 x DC-DC 700mA LED Driver (LuxDrive BuckBoost 700mA, A011-D-V-500): $18 each
2 x DC-DC 500mA LED Driver (LuxDrive BuckBoost 500mA, A011-D-V-700): $18 each
2 x DC-DC 250mA LED Driver (LuxDrive BuckBoost 250mA, A011-D-V-250): $18 each
6 x 6 Ohm 50 watt resistors: $45 total
Left and Right static LED headlight assembly for a US Spec 2015-2018 Mercedes Benz C300: $300-$800

Skill Level:
Advanced (8/10)
Soldering skills required
Reading and understanding voltage, current and continuity
Operating a digital multimeter
Ability to disassemble the headlights and grill of the vehicle

Courage Required:
Medium (7/10)
Willingness to tear into a $50k Mercedes (ok a $47k Mercedes because you skipped the LED headlights)
Willingness to destroy a $300-$800 set of headlights by melting them or shorting them out

Time:
~20 hours

Sourcing Headlights:
Headlights can be sourced off e-bay. Read the E-Bay seller's notes carefully for any damage. Damage can make the assemblies difficult to mount (broken tabs) or may lead to water ingress into the assemblies (impact damage). Headlights can be sourced without the "LED Modules" or "Ballasts" but at a minimum, the LED module in the upper outside corner of the headlight is required. There is no difference among the model years. Assemblies sourced outside the US may have differing wiring or additional modules.

Assemblies cost approximately $400 each in like new shape with no scratches or damage. Mine came with both modules, all the mounting hardware and the rubber gap seals.

Assemblies missing components or with damage can cost as little as $150. All assemblies will contain the LED modules for the high beams, low beams, turn signals and side marker light. The module for the daytime running light is removable and may be missing. If you purchase a headlight without this module, you will need to purchase this separately. The module on the underside of the assembly is not required but is desirable as it seals the headlight and acts as a heatsink.

"Headlight module" is a reference to one of the two metal assemblies attached to the outside of the housing and removable via a number of screws. In an eBay listing, these may be referred to as "LED modules", "Ballasts" or "Controllers". For the static headlights in the US, there are two of these modules for each headlight. One is located at the bottom of the headlight assembly. It is approximately 3"x4" with a depth of 1". This assembly contains the controllers for the LEDs. I'll refer to it as the "Controller Module". This unit is held in place with 4 Torx screws.

The second module is approximately 2" square and contains the LED module and heatsink for the daytime running lights (DRL's). I'll refer to this module as the "DRL Module". This unit is held in place with 3 Torx screws. Note that a rubber gasket is used to seal the joint with the headlight. Be sure this gasket is present if you order this module separately from the headlight.

Care must be taken when handling the DRL module as the LED's are exposed and vulnerable to damage when it is removed from the headlight assembly.

Note that when ordering these modules separately, you will need the mounting screws for them.

Driving LED's:

Headlight assemblies like these use high brightness LED arrays. Each beam assembly is made of multiple LED's. To illuminate an LED, which is a diode, a minimum amount of voltage is needed. This is called forward voltage or Vf. When LED are assembled in a string or matrix, the voltage required to illuminate the assembly increases. In the case of headlights, forward voltage is usually well above the voltage supplied by the car. Voltage requirements for LED headlight modules can be well above 40V, requiring a voltage booster to light off the LED's. Once illuminated, the LED starts producing both light and heat. Left unchecked, as heat rises, resistance starts dropping allowing more current through the LED. Very quickly, the LED will experience thermal runaway, exceeding 160 degrees C, with higher heat allowing ever more current through until the LED destroys itself. Thus a means to limit current is required for longevity in LED's. With low power LED's a resistor will do. With high brightness LED's a current limiting driver is required to maximize performance and LED life. Most LED drivers limit current to a constant value. This is a practical way to drive an LED without overly complex circuitry. The design in this write-up uses constant current boosting LED drivers to run these LED modules.

The LED modules for the high beams, low beams, turn signal and DRL's cannot be driven directly from a vehicle's 12V system. Even if the forward voltage of the LED assembly is low enough, unlimited current will destroy the module quickly. Therefore it is unwise to hook any of these LED modules up to a direct battery connection. The exception is the side maker light. The headlight assembly contains the LED driver necessary to run this light and 12V can be fed directly to it.

Mercedes Design of the Static LED's:

Mercedes, being very German, designed the static LED headlights to very high standards. Their design ensures long life for the LED's, exact color temperature of the emitted light and integrates seamlessly with all the other vehicle systems. The static LED's being the simplest of the LED headlight offerings has the fewest features; however, some of the design complexity needed for such things as active headlights, is partially incorporated into the design of the static LED headlights.

Therefore, the design of the electronics of the headlight is unnecessarily complex for the simple functionality but is retained for the sake of standardization among the LED headlight assemblies. While I won't cover all the components needed to drive these headlights, I'll cover the main components here.

Mercedes LED Drivers:

Each controller module contains two ON Semiconductor high current dual channel driver chips. Each chip can drive two LED strings or modules with up to 1.6 amps of current at 60VDC. One chip drives the high beam and low beam assemblies, the other drives the turn signal and DRL assemblies. These are constant current drivers, but they can vary the current based upon any number of preprogrammed factors. In the case of these headlights and DRL's, Mercedes uses LED module base plate temperature to protect the LED's from over-temperature damage. The design sends a fixed current to the LED modules, but if the temperature limit is exceeded, the driver reduces the current or removes power entirely. This protection is implemented for the high beam, low beam and DRL. The turn signal LED's are not monitored for temperature. To measure the LED temperature, Mercedes uses a thermistor on each LED assembly. This serves as a proxy measurement of the LED's junction temperature, which is the critical controlling factor in the life of the LED. Thermistor resistance values are captured by a separate ON Semiconductor chip and are used to set the current fed to each LED string. Information is passed between these three semiconductor chips via a local interconnect network (LIN). Commands for the headlight module (i.e. low beams "ON") are passed to these modules via a CAN bus through a CAN buss controller and onto the LIN. Status is relayed to the vehicle using the same system.

Therefore, it is not possible to hack the existing controller module to run the headlights. We need separate drivers. I chose to use constant current LED drivers, as the simplicity of these drivers gives up little in bulb life while greatly reducing the complexity of the system.

Replacing the Mercedes LED Drivers:

Replacing the drivers requires knowing a significant amount about each LED module. One needs to know the forward voltage, maximum junction temperature limit and current limit at a minimum. While I was able to determine a lot about these headlights, forward voltage and current limits were not available. Searching the internet, I did determine that Mercedes low beam LED headlights like this use a combined total of 34 watts.
Assuming this was measured at a nominal 13.5V, this would indicate that each low beam headlight is using around .800mA of current. This seems about right and servs as a starting point. Using a variable voltage, current limiting power supply, I was able to directly drive each headlight module, first determining the forward voltage, then experimenting with the current limit to see where an increase of current fails to yield a commensurate increase in LED brightness. I determined the thermistor resistance/temperature and read the LED module temperatures by measuring the resistance across the thermistor. This method allowed me to graph the performance of each LED cluster and estimate the maximum safe operating current. The temperature values were further confirmed by taking direct thermocouple readings off the DRL module. Note the turn signal does not have a thermistor, therefore it was likely designed to run at a set current.

To prolong LED life, I chose to keep the measured temperature at the LED assemblies below 60 degrees C. This equates to an LED junction temperature of between 80-90 degrees C.

For more details on the performance and testing of these headlights, I'll be posting another thread with the test data.

Wiring the Headlights:

As stated before, I wanted to avoid modifying the Mercedes harness. This meant all the changes needed to happen within the headlight. My goal was to minimize the changes to the headlight and avoid and warnings from the vehicle. The changes I made to the LED headlight assembly are not readily reversable. The controller modules were disassembled, likely destroying the electronics, but the heatsink was retained. No changes were made to the LED assemblies within the headlight housing.

Headlight Plug Preparation:

Rewiring the headlight starts with rewiring the headlight socket. This socket contains spots for 14 pins. The LED headlight socket uses 7 pins. The halogen plug from the car, while physically compatible, uses 6 to 10 pins. We will only use five of them as we have to drive the DRL's off the side marker circuit. The halogen DRL circuit operates at a lower voltage and current than the Static LED DRL, thus the Static LED DRL only dimly illuminates when run off the halogen DRL circuit. So we eliminate one of the pins. Only 1 of these pins are used in common between the two sockets, which means 4 pins need to be reconfigured within the Static LED headlight socket. This requires snapping the socket loose so it can be pulled out through the hole for the controller module.

1. Remove the controller module from the headlight, disconnecting both the 32 pin plug and the two pin plug from the module.
   
   http://www.endoimage.com/Mercedes/P1080379.JPG
   
   http://www.endoimage.com/Mercedes/P1080380.JPG
   
   http://www.endoimage.com/Mercedes/P1080381.JPG
2. Remove excess plastic from the opening for the controller module, allowing more room within the headlight assembly.
   
   http://www.endoimage.com/Mercedes/P1080387.JPG
3. Using a Torx T-20 bit and a ratcheting wrench, remove the Torx screw holding the white wire conduit in place within the headlight.
   
   http://www.endoimage.com/Mercedes/P1080392.JPG
4. Unsnap the headlight plug from the headlight assembly by pushing the two mounting tabs in. The plug can be pushed into the headlight assembly.
   
   http://www.endoimage.com/Mercedes/P1080396.JPG
5. Push the plug into the assembly and work it towards the controller opening. This may take a fair amount of effort. Once the plug is fully inside the assembly, the white plastic wiring conduit may need to be opened allowing more slack for the headlight plug wiring. If there is still not enough slack to push the plug out through the controller module opening, there may be one or more wires that do not have enough length. These wires should be marked and cut 1/2 inch from the plug, leaving enough wire exposed to strip and solder through the headlight plug hole.
   
   http://www.endoimage.com/Mercedes/P1080397.JPG
   
   http://www.endoimage.com/Mercedes/P1080401.JPG
   
   http://www.endoimage.com/Mercedes/P1080402.JPG
6. With all the necessary wires cut, push the plug through the assembly and out the hole for the controller module.
   
   http://www.endoimage.com/Mercedes/P1080403.JPG
7. Extend the cut wiring by adding on 7" pieces of wiring at the headlight plug hole, being sure to match the gauge of the cut wires. Apply heat shrink to these splices.
   
   http://www.endoimage.com/Mercedes/P1080404.JPG
   
   http://www.endoimage.com/Mercedes/P1080405.JPG
8. With the headlight plug pulled out the controller opening, unclip the pink retainer clip from the back of the headlight plug.
   
   http://www.endoimage.com/Mercedes/P1080407.JPG
9. Mark the wires going to the headlight plug with their respective pin assignments. This will allow you to identify the wires after they are de-pinned.
10. Prior to proceeding, note the following:
    1. When rerouting wires from one pin to another, change the wire's location within the pink retainer to correspond with their new pin assignment.
    2. Don’t forget to install heat shrink prior to re-splicing wiring.
    3. To swap pins, cut the old wiring as close to the pin as possible. Strip and tin the new wire. Tin the pin. Solder the new wire to the pin. Removing the old wiring from the pin is not possible without destroying the pin.
    4. Prior to shrinking the heat shrink, test all the connections per Step 12.
    5. De-pinning the headlight plug can be accomplished by pressing a 3/64" jeweler's screwdriver into the holes adjacent to the pin on the face of the headlight plug.
11. De-pin and reconfigure the wires in the following manner:
    1. De-pin Pin 10. Remove the pin and retain it. Cut one of the wires from Pin 5 without removing the pin. Twist together the wire from Pin 10 into the wire from Pin 5. Tin the connection. If you had to cut one of the wires from Pin 5 during Step 5, solder the extension into the twisted connection you just created using a soldered lap joint. Remember to add heat shrink prior to soldering the splice together. Pin 5 is now the ground wire for the headlight assembly.
    2. De-Pin Pin 2. Remove the small pin and replace it with the large pin retained in Step 11a. Install this pin in the location for Pin 8. This pin is the positive voltage for the turn signal.
    3. De-pin pin 1. Remove the pin and strip the wire. De-pin Pin 4. Remove the pin and stirp the wire. De-Pin pin 6. Remove the pin and strip the wire. Splice together the wires from pins 1 and 6. Connect the smaller style pin from pin 4 to the spliced wires. Insert the pin back into the location for pin 4. Solder the larger pin from pin 6 to the wire from pin 4. Insert this into the location for pin 6. Pin 4 is now the positive voltage for the DRL and side marker light. Pin 6 is now the wire for the positive voltage for the low beam lamp.
    4. Move the pin from pin 9 to the location for pin 7. This is the positive voltage for the high beam lamp.
12. Test for continuity between the headlight plug and the controller plugs (Note the Controller Plug is the 32 pin plug and the Controller Power Plug is the 2 pin plug) :
    1. Pin 4 on the headlight plug to pin 32 on the controller plug
    2. Pin 5 on the headlight plug to pin 1 on the controller power plug
    3. Pin 6 on the headlight plug to pin 14 on the controller plug
    4. Pin 7 on the headlight plug to pin 2 on the controller power plug
    5. Pin 8 on the headlight plug to pin 16 on the controller plug
    6. Any additional pins that have not been modified do not need to be tested.
    7. If you have a 12V power supply, you can test the function of the side marker lights by connecting positive 12 volts to the wiring for pin 4 and connecting the ground to the wiring for pin 5.
13. Once the wiring continuity tests are completed, shrink the heat shrink used on the splices.
14. Press the pink retainer back into position on the headlight plug.

Adding the Resistors:

To avoid headlight malfunction errors from occurring, the vehicle needs to be tricked into believing the halogen bulbs are still connected. This applies to the high beam, low beam and turn signal circuits. The DRL and side marker light circuits are not monitored.

Unfortunately, this means simulating the loads of the halogen bulbs, thus requiring resistors. The resistors draw current by creating and dissipating heat. The removes the energy efficiency advantages of LEDs. It’s the only real trade-off required for this modification.

To dissipate the heat as effectively as possible, I chose to repurpose the controller module's aluminum housing. I made the following modifications:

1. Remove the controller board. First remove the 6 T-8 Torx screws holding the metal shield to the heatsink. Remove the shield, exposing the board. Remove the board by prying it from the heatsink. Using a prying tool may allow removal without damage to the board, but significant force may be required to free the board due to the heatsink compound/adhesive applied by the factory.
   
   http://www.endoimage.com/Mercedes/P1080382.JPG
   
   http://www.endoimage.com/Mercedes/P1080383.JPG
   
   http://www.endoimage.com/Mercedes/P1080384.JPG
2. Clean the heatsink of residual compound.
   
   http://www.endoimage.com/Mercedes/P1080385.JPG
3. Using the metal cover as a template, create a square metal base plate for the resistors that mounts to the heatsink using two of the existing T-8 screws. Secure the resistors to the plate using 4 4-32 flat head screws and nuts. I applied heatsink compound (used under PC processors) between the resistors and the mounting plate and between the mounting plate and the heatsink. This helps maximize thermal transfer.
   
   http://www.endoimage.com/Mercedes/P1080408.JPG
   
   http://www.endoimage.com/Mercedes/P1080409.JPG
4. Strip and twist together all the wires from one end of the resistors. Lap splice them to a single wire and add heat shrink.
   
   http://www.endoimage.com/Mercedes/P1080410.JPG

Wiring the connector plugs and drivers:

In this section we modify the 32 pin plug and 2 pin Controller Power plug for the controller module. De-pinning is only required for the below pins. To de-pin the 32 pin plug, with the locking mechanism removed, use a sharp object or a 3/64" flat head screw driver to press in on the side of the pin through the opening in the side of the plug. Do this while applying steady pressure to the wire. For the two pin plug, simply cut and strip the wires after labeling them.

Wait to shrink the heat shrink until all the connections have been tested for continuity.

De-Pining the 32 Pin Plug:

1. Remove the locking mechanism from the plug by removing the plastic plate on the taller edge of the plug, then slide the internal plug out to the side.
2. Label the following wires. Include the function and pin location allowing easier troubleshooting:
   
   Controller 32 Pin Plug:
   2 - Turn Signal +
   4 - Low Beam +
   5 - High Beam -
   14 - Low Beam + In
   16 - Turn Signal + In
   17 - DRL +
   19 - High Beam +
   21 - DRL -
   22 - Turn Signal -
   23 - Low Beam -
   32 - DRL + In
   
   Controller Power Plug (PP):
   PP 1 - Ground
   PP 2 - High Beam + In
3. Prepare the LED drivers in the following manner:
   1. Trim the bare piece of wire from each of the drivers dimming wires (purple and grey wires). Trim one of the dimming wires on each driver to be at least 1/4" shorter than the other. Bend the wires back and cover them in heat shrink. This step is necessary to prevent the dimming wires from touching which turns off the driver.
   2. Twist all the grounds of the drivers together. Tin the connection.
   3. Label the drivers with the in accordance with the following:
      1. Label one of the 500mA drivers as "Turn"
      2. Label the other 250mA driver as "DRL"
      3. Label one of the 700mA drivers as "Low Beam"
      4. Label the other 700mA driver as "High Beam"
   4. Twist together and tin each of the red wires from the driver to one of the loose ends of one of the resistors for the following drivers: High Beam, Low Beam and DRL.
   5. Strip and twist together the "PP 1 - Ground" wire with the three wires twisted together in Step 3b. Tin the connection.
   6. Slipping heat shrink over the wires first, solder together the two sets of joined wires from Step 3b and Step 3e. This step ties the driver grounds and the resistor grounds to the ground to the vehicle. This is a soldered lap splice, which is the only practical way to connect these wires.
4. Splice together the connector wires to the drivers, but do not shrink the heat shrink yet:
   1. Placing heat shrink over the wire first, strip and splice together the red wire assembly from the High Beam driver to the "PP2 - High Beam In" wire using a lap splice.
   2. Placing heat shrink over the wire first, strip and splice together the white wire from the High Beam driver to the "19 - High Beam +" wire using a lap splice.
   3. Placing heat shrink over the wire first, strip and splice together the blue wire from the High Beam driver to the "5 - High Beam -" wire using a lap splice.
   4. Placing heat shrink over the wire first, strip and splice together the red wire assembly from the Low Beam driver to the "14 - Low Beam + In" wire using a lap splice.
   5. Placing heat shrink over the wire first, strip and splice together the white wire from the Low Beam driver to the "4 - Low Beam +" wire using a lap splice.
   6. Placing heat shrink over the wire first, strip and splice together the blue wire from the Low Beam driver to the "23 - Low Beam -" wire using a lap splice.
   7. Placing heat shrink over the wire first, strip and splice together the red wire assembly from the DRL driver to the "32 - DRL + In" wire using a lap splice.
   8. Placing heat shrink over the wire first, strip and splice together the white wire from the DRL driver to the "17 - DRL +" wire using a lap splice.
   9. Placing heat shrink over the wire first, strip and splice together the blue wire from the DRL driver to the "21 - DRL -" wire using a lap splice.
   10. Placing heat shrink over the wire first, strip and splice together the red wire from the Turn Signal driver to the "16 - Turn Signal + In" wire using a lap splice.
   11. Placing heat shrink over the wire first, strip and splice together the white wire from the Turn Signal driver to the "2 - Turn Signal +" wire using a lap splice.
   12. Placing heat shrink over the wire first, strip and splice together the blue wire from the Turn Signal driver to the "22 - Turn Signal -" wire using a lap splice.
5. Test the connections for continuity from the headlight plug to the drivers:
   1. Pin 4 on the headlight plug to the splice connection containing the red wire for the DRL driver
   2. Pin 5 to the splice connection for the ground wires
   3. Pin 6 on the headlight plug to the splice connection containing the red wire for the Low Beam driver
   4. Pin 7 on the headlight plug to the splice connection containing the red wire for the High Beam driver
   5. Pin 8 on the headlight plug to the splice connection containing the red wire for the Turn Signal driver
6. Bench Test the Assembly (recommended if you have a power supply):
   
   http://www.endoimage.com/Mercedes/P1080412.JPG
   1. Set the power supply to 13.5V with an over-current limit of 5 Amps. If you have a fixed supply make sure it has a maximum current limit of at least 5 amps.
   2. Make sure that the heat shrink is covering the splices as it may slip as we have not shrunk it yet. We want to avoid having splices touch, but need access to the splices for testing purposes.
   3. Connect the ground side of the power supply to the splice for the ground connections.
   4. Test the low beam driver by connecting the positive lead to the splice connection containing the red wire for the Low Beam driver. The low beam should illuminate.
   5. Test the high beam driver by connecting the positive lead to the splice connection containing the red wire for the High Beam driver. The high beam should illuminate.
   6. Test the Turn Signal driver by connecting the positive lead to the splice connection containing the red wire for the Turn Signal driver. The Turn Signal should illuminate.
   7. Test the DRL driver and side marker light by connecting the positive lead to the splice connection containing the red wire for the DRL driver. The DRL and side marker light should illuminate.
7. Test the Assembly on the vehicle:
   1. Being carefully to keep the heat shrink over the spliced connections, open the hood of the car and place the headlight assembly as close to the headlight location as possible.
   2. Disconnect the headlight plug from the vehicle's halogen headlight. This is accomplished by prying open the small retaining tab on top of the plug, then pressing down on the tab while removing the plug.
   3. Connect the plug to your modified LED assembly.
   4. Turn the ignition onto the accessory setting. The DRL and Side Marker lamp should illuminate.
   5. Turn the ignition to the on position. The high beams, low beams and turn signal should function.
   6. Start the vehicle. Briefly put the vehicle into and out of drive and reverse. Let the vehicle run for a few minutes testing the high beams, low beams and turn signal. Any bulb malfunction error will occur at this point. If no error occurs, you have successfully completed the conversion of the wiring for the LED headlight
8. Carefully disconnect the LED headlight from the vehicle.
9. After checking the positioning of the heat shrink, shrink all the heat shrink over the splices in the headlight wiring.
   
   http://www.endoimage.com/Mercedes/P1080414.JPG
10. Re-assemble the headlight by first placing all the wiring into the housing, followed by the LED drivers. The drivers will be loose inside the headlight assembly, but this should pose no problems as the assembly is largely empty on that side.
11. Place the controller heatsink back into position, being careful not to pinch any wiring in the process. Secure it with the four screws.
12. Re-test the assembled headlight on the vehicle as done in Step 7.

Installing the Headlight on the Vehicle:

http://www.endoimage.com/Mercedes/P1080416.JPG

I'm not going to cover all the steps for removing and replacing the headlights on the vehicle, but will cover the important points:

1. To facilitate a rough alignment of the LED headlights, prior to removing the halogen lights, park the vehicle pointed towards a wall at a distance of 10' or greater. Using painter's tape, mark the location of each tire on the ground. Using painters tape, mark the cut-off line of the headlights on the wall. Locate the brightest part of the headlight beam for both headlights and mark that with tape.
2. To access the rear of the headlight, turn the wheels of the vehicle away from the side of the vehicle on which you are working for access inside the fender well.
3. To access the rear of the headlight, you will need to remove the fender liner access panel and loosen the fender liner. To loosen the fender liner, remove the four push pins holding the fender liner to the bumper cover. Three are inside the fender well lip and one is at the lower corner of the bumper cover facing downwards.
4. To remove the headlight, you will have to loosen the bumper cover. This is accomplished by first removing the two screws holding the bumper cover to the fender. These are accessible after loosening the fender liner and pushing it aside. Secondly, you will need to remove the 5 screws holding the bumper cover and grill to the radiator cross member. Two of these screws are located at the inner corner of the headlight just inside the grill with one on each side of the grill. Use caution when removing or inserting these screws as dropping them into the grill makes them difficult to retrieve. The last three screws are at the top of the grill and are easy to see and remove. Both a mechanical and magnetic bolt retriever are useful for retrieving dropped screws and starting the more inaccessible screws.
5. To remove the headlights, pull the bumper cover loose. Use painters tape to protect the edges of the bumper cover from the sharp edges of the headlight assembly.
6. Three bolts/screws hold the headlight assembly in place. Two are on top and one is accessible through the wheel well. Once removed, twist and wiggle the headlight assembly loose while gently holding the bumper cover out of the way. A second set of hands will be helpful.
7. Reinstallation is the opposite of removal.
8. Using the reference points you marked in step 1, position the vehicle in the exact position used to mark the aim of the headlights.
9. Using the adjusters and ensuring the high beams are off, aim the headlights to the approximate aim point as the halogen headlights.
10. Repeat all of the above from the very beginning for the other headlight. Don't worry, once you've done it once, the other headlight is easy.
11. With both LED headlights completed and installed, test the headlights at night. The location of the cut off line for the low beams is critical for not blinding other drivers. Dial in this adjustment by finding a level parking lot with an adjacent wall. Park the car at least 50 feet away and make sure the headlight's cutoff line is slightly below the level of the headlights. Don’t rely on reflections of road signs as an indication of headlight aim as both the DRL's and turn signals are quite bright and can reflect off signs from quite a distance. There are no aiming provisions for the high beams.

You are done. Go crack open a cold one and enjoy the satisfaction of your handy work knowing you are one of very few to try and succeed at this. Then post this to a Mercedes forum and await people telling you how great you are!

Old Ag

Wether it will void the warranty is upto your dealer, but it shouldn’t except for the headlights, of course.

A plug and play solution is not possible without either having very dim DRL’s or by just settling for the DRLs working as parking lights. Your plug and play lights will need an external wire for the DRL’s to get enough amperage to operate correctly.

And even operating the way mine do, this is a significant improvement. The DRL lamps do operate, they just don’t quite work the way they used to. The only difference is that there is nothing illuminated when the light switch is in auto during the daylight. This can be fixed, but it takes additional wiring and relays under the hood.

Lastly, my solution is much less than $1400 US. I payed top dollar for my OEM headlights and the whole thing was still under $1000. You can do it for less than $500 if you do well finding the headlights. But, if I had to do it over, I would have bought the car with the LED headlights.

Old Ag

Unfortunately, I did not take photos of the headlight removal and replacement. My hands were to full to operate the camera!

Old Ag