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European Headlight Assembly

This component is part of Lights.


Reflectors in European Light Assemblies are more important than those in US Light Assemblies which use a Sealed Beam unit with a reflector as part of the bulb.

Euro Headlight by Bosch

This is a description of a the typical EUROPEAN style (or, let's better say: non_US) headlight made by Bosch. The light is a genuine Mercedes replacement part for 113 cars with part number A113 820 04 61 (LHD vehicles) and A113 820 03 61 (RHD vehicles). Euro style headlights are still available now (2012) in Bubble Glass or Flat Glass styles but are very expensive.

Flat Glass Headlamp

Picture showing a flat glass headlamp: The flat glass headlamps were a factory option available from 03/1970 and use two separate H1 halogen bulbs for the main and dipped beams.

The Bubble (Rounded) style is seen more often than the flat style. The Bubble shape is believed by some owners to better withstand pebbles and other road hazards because of its rounded shape.

The Headlight described here was made for Bosch (or by/for Bosch) in the Czech Republic with a manufacture date of June 2004. It was purchased new in late 2007.

General overview

These Euro headlights are designed to give an assymetric beam when dipped, so they light up the kerb side much further than the road in front without blinding oncoming traffic. This way, cyclists and pedestrians can be seen much earlier than with a normal flat beamed headlight. For this reason, the headlights for LHD and RHD cars are left-right reversed and therefore not interchangeable. The same light assembly is used for the Driver and Passenger sides of a car. Two internal screws adjust the beam horizontally and vertically. A third adjusting screw is used to move the Fog Light beam up or down.

LHD Headlamp Lens Marking

Picture showing lens markings on a LHD car: The parking light bulb in a LHD headlamp is fitted below the main bulb.

RHD Headlamp Lens Marking

Picture showing lens markings on a RHD car: The parking light bulb in a RHD headlamp is fitted above the main bulb

Main Components

The main components of the headlight are the Glass Lens and the Headlight Assembly. The Assembly contains five bulbs: Main Beam, Turn Signal Flasher, Fog Light, Parking Light, and a European style low power Night Light often called a Clearance Light. This low power bulb is intended to mark a car parked in an unlit area for perhaps the entire night and can only be engaged left side or right side but not for dual use. This type of light is not commonly used in the USA but rather supposed to be a German (or European) speciality. There are also three reflectors: indicator/turn signal, main headlight with parking light and the third one for the fog/clearance light.

North American drivers sometimes use the Parking Light for a similar purpose but as a typical US Parking Light draws more current than a traditional Clearance Light, a Parking Light is not usually activated for long periods of time in the US.

Glass Lens

LHD Euro Headlamp

The lens is molded in one piece having three different glass patterns to give each of the three major bulbs the best visibility. The center of the Bubble Lens extends about 3 inches (about 7.6 cm) out from the Assembly. The Lens is clear glass

Bulb Detail - RHD Headlamp

Flat Glass Headlamp Chassis

Flat Glass Headlamp Chassis. Note the separate dip/main beam bulb slots

Lens "Spidering"

Some owners have commented on thin spider web-like lines that can be seen on the face of newer Lenses especially around the "CR" sign upon close examination but which were absent on older lenses. These lines occur during manufacture most likely because of old and slightly worn casting molds. The lines do not affect function and are not obvious to the casual viewer. Each Lens goes through inspection for defects. Bosch inspectors do not reject a Lens with some slight spidering.

Lens Design

The glass Lens is held to the Assembly by six “C” shaped metal clips, which are not separately available. The Lens fits tightly against a rubber seal fitted to the outer edge of the Assembly. The glass Lens does not need to be removed from the Assembly base when replacing bulbs.

The Lens of the headlight discussed here has markings molded into the glass. These markings and numbers may vary on other lenses depending upon manufacture date, plant location, and design modifications. The markings on the example Lens are: CR in a square; E in a circle; 4473; BOSCH; 1305630005; A in a circle; 1193; Neigung 20cm auf 5m [“Inclines 20cm in 5 m”]; and a wave symbol marked K 23368. Older lenses carry the little Bosch "coil sign" instead of the CR in a square, which indicates that they were still manufactured in Germany. These lenses also carry the inscription "Importe d'Allemagne". These latter two inscriptions were replaced by the CR in a square when the production was moved to the Czech Republic.

Headlamp Adjustment

Headlight Assembly

The “Headlight Assembly” refers to the headlight unit except for the glass lens and the Chrome Surround. The Chrome Surround itself is made of chromed zinc diecasting (and is as such identical with the chrome surround of the US-headlight units). The Assembly includes the five bulb holders, wires from the bulb holders, a Circuit Board, fastening screws and adjusting screws. A rubber seal on the inside edge of the Assembly frame ensures a snug fit between the Assembly and the car body.

Assembly Components

The Assembly components are arranged and fastened to an aluminum frame.

  • The upper bulb holder (Turn Signal) is labeled “18 W” [watts]. This bulb is behind an Amber (Orange) plastic cover. The lower bulb holder of the headlight assembly houses the Fog Light and the Night (Clearance) Light which is labeled “3W”.
  • The main bulb holder is connected to two screws at the 10 o’clock and the 5 o’clock positions. These screws are used to adjust the beam of the main light to avoid dazzling an approaching car.
  • A miniature Parking Light bulb is located (and partially hidden) under its connecting parts below the main bulb socket.

Each of the bulbs is powered and controlled from the Circuit Board except for the main headlight bulb. The contacts protruding from this bulb fit the connector from the car which powers and controls this bulb.

An unmodified Circuit Board has 5 pins. Recent circuit boards are made of plastic, earlier versions were made of "Pertinax", a synthetic resin bonded paper (a composite material made of paper impregnated with a plasticized phenol formaldehyde resin) and easily tend to break. The wires from the bulb holders are connected to these pins. A sixth pin space on the Circuit Board is empty and could theoretically be used for connecting additional wires for a side fender light, as an example.


The reflectors are made of thin sheet metal and silverized but tarnish over time and even rust. Lighting then becomes very poor. Some owners have them rechromed or replacement reflectors are available from MB or Bosch.

Installing and Replacing Bulbs

Be sure that the copper contacts are correctly placed after installing each bulb.

The entire Headlight Assembly should be removed from the car and pulled forward to access the rear of the Assembly. Do not remove the glass lens from the lamp.

Installing the High beam/Low beam headlight bulb

At the back of the Assembly locate the aluminum socket on the headlight bulb housing. Disconnect the electric plug from this lamp.

To remove the Socket: push in (down) on the socket while rotating counterclockwise. The socket will come free of the light housing except for the wires for the Parking Light bulb. (A new light unit has a plastic mask in the main light socket hole that must be removed before inserting a bulb for the first time.)

Installing the Parking Light Bulb

The Parking Light bulb is placed into its opening while the main bulb socket is lifted away from the housing.

Re-attaching the Socket: Push down on the socket while lining up the socket holes with the tabs on the lamp housing. When all three socket tabs are under the holes in the socket rim and the Parking Light bulb is seated properly, turn the socket to lock it in place.

Installing the Turn Signal bulb

At the back of the Assembly use a Philips head screw driver to slightly loosen (do not remove) the holding tabs on each side of the bulb unit located near the top of the Assembly. Turn the now loosened tabs away from the bulb unit. The entire chrome bulb housing can now come free tethered only by the wires.

Remove the bulb by pushing in slightly and turning the bulb until the bulb comes free. Installation of the bulb and the housing is the reverse. The Amber (orange) mask will remain in place and need not be removed for bulb replacement.

Fog Light and Night Light (Clearance Light) bulbs

Both these bulbs are in the lower part of the Assembly. The lower chrome housing for these bulbs and the Circuit Board are not removed when replacing these bulbs. Only the aluminum boat shaped upper socket is removed.

From the rear of the Assembly locate the boat shaped aluminum socket for these bulbs. The socket unit is fitted to the lower chrome housing by a copper or brass color curled Holding Tab.

The Tab is at the bottom center of the Headlight Assembly to the right of the Fog Light Adjusting Screw. The socket unit is held by the Curled holding Tab, by a small tab on the opposite side of the socket, and finally by a slight pressure fit between the Socket unit and the chrome housing.

While holding the edges of the boat shaped socket with two fingers (the edge alongside the Night Light bulb may give the best grip), use the other hand to carefully pull the Holding Tab back slightly lifting it off the socket unit, then rotate the bottom edge of the Socket unit up and away from the chrome base, rotate up not around.

With gentle upward pressure the Socket will come free of the chrome base. Note the small tab used to position and anchor the socket to the chrome housing at the top edge of the socket unit. As the socket rotates up and comes free from the chrome housing, this tab will come out of its slot to free the socket.

After installing the replacement bulb or bulbs, reverse the steps to re-install the socket. Pull the Holding Tab back, position the socket over the chrome base while placing the small tab into its correct position then gently press down on the socket unit until it locks to the chrome base then release the Curled Tab.

Bulb Sizes

  • The main Headlight bulb is a 40/45 watt non-halogen (Bilux) bulb that can be upgraded today. The correct replacement therefore carries the designation "Halogen BILUX-AS-HALOROAD R2 12V P45t" (available from Osram or Philips) and is a special 45/40 watt halogen substitue for greater light output and longer life. It's very similar to the regular (European) 60/55 watt H4 halogen bulbs but with a slightly lower output (barely visible) and with the correct P45t socket for the old-style mirrors used on the W113s. The bulb has three projecting connectors to fit the car’s internal connector.
  • The Parking Light is a miniature bayonet bulb T4W on a BA9s base. An upgrade is available as 3886X to give more light. Replacements include: 3893, 57, 57X, 1891, 1893, 1895, 78223.
  • The 18 Watt Turn Signal bulb can be upgraded to a P3497 higher intensity bulb.
  • The Fog Light bulb is a 35 watt bulb on a BA20s base.
  • The Night Light (Clearance) bulb is a 3 Watt bulb on a BA-15s base. An upgrade is available to a more modern R5W bulb.

Installing the Headlight Assembly to the Car

The Assembly is held to the car by four Phillips head screws located around the edge of the housing. These are flat head screws grey in color. Do not confuse these four mounting screws with the two round head copper colored screws used to adjust the position of the main bulb.

Attach the connectors from the car to the main light and to the Circuit Board. Arrange the wiring behind the assembly as you fit the light unit to the car body. Position the assembly and then tighten the four mounting screws.

The Assembly is further fixed in position by the Chromed Surround. Hook the Surround to the fitting at the top of the Assembly then use the single screw at the bottom of the Surround to secure it to the Assembly. The holding screw goes through the Surround into a hole at the bottom of the Assembly. The screw does not go into the body of the car.

Light Switch Positions

The first click of the light switch to the right lights the Parking Light.

The second position lights the Main Light. High or Low beam is selected by the foot switch. On Euro wired cars a momentary beam change can be made by pulling up on the steering column stalk.

The Fog Light is activated by pulling the light switch up away from the dashboard while the main lights are on.

The Turn signals are activated by moving the steering column stalk handle when the ignition is in the second position.

The Clearance Night Light is activated when the ignition is off and the light switch is turned to the left one click for the left light, two clicks for the right light. This function may not work on some cars.

Adjusting the Main Light and Fog Light Beams

Adjusting screws are accessible when the headlight is installed on the car and the Chrome Surround is removed.

Two round head brass color screws located at the sides of the headlight are used to adjust the main light in two dimensions. A third adjusting screw for the Fog Light is at the bottom of the headlight assembly.

Adjustment should be done according to local rules and should follow detailed instructions available elsewhere.

Wiring USA Fender Lights to a Euro Headlight

Here is a step by step procedure to wire a Euro style headlight to a USA style fender light (side marker light).

The Euro headlight assembly has a 6-prong male connector Circuit Board. Only five of the connectors are used out of the box. The 6th position is an empty unused hole. The standard USA fender sidelight has two male prongs.

The following procedure does not require cutting wires and allows easy return to the original wiring profile.

Materials needed for each side:

  1. Bullet electrical connectors, one male and two female.
  2. Two 1-foot long lengths of 14 gauge wire.
  3. One circle eyelet electrical connector.
  • Connect one male and one female bullet connector to one wire.
  • Connect one female and one circle eyelet to the other wire.
  • Connect the male end of the wire that has one male and one female end into the 6th hole of the Circuit Board. There are now six male connectors on the Circuit Board.
  • Next connect the female end of this same wire to either one of the two male connectors on the sidelight.
  • Connect the six connector female harness to the Circuit Board.
  • The other wire has the female connector and the circle eyelet connector.
  • Attach the female end of this wire to the other male prong of the two prong (male) side light wire.
  • Ground the other end of this wire to the bottom of the light bucket using a sheet metal screw through the eyelet.
  • Further modification may be necessary to have a side fender light blink with the turn signal.

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