The 1986 through 1994 300E, 300CE, and 300TE were never noted for their great headlights; here’s how to improve them.

The stock headlights on our 1988 300TE were less than amazing. Then, to avoid stone chips we had installed stick-on plastic headlight protection, but as the plastic aged, it diffused the light. Our night vision is also not what it used to be, so when Technical Editor Stu Ritter showed us the European 500E lights he’d put on his 400E (with a European dash-mounted height adjuster), we quickly said, "Let’s do it!"

What You Need

Left headlight assembly, Hella part 1EJ 004 440-111 (for 1986-89 models)

Right headlight assembly, Hella part 1EJ 004 440-121

Two 12v H4 halogen 100/80-watt high/low-beam lamps, Osram 64194

Two 12v H3 halogen 80-watt fog light lamps, Osram 64153

Two starter booster relays, Volkswagen 431 951 253H

Two relay holders, Hella 87123

Eight Hella female spade connectors that clip into the relay holder sockets, Hella 87272

Two six-pin electrical connectors, Mercedes-Benz part 006 545 80 28 (socket) and 009 545 30 28 (cover)

Six feet of 14-gauge insulated wire, push-on terminals, butt-type wire connectors, heat-shrink tubing, grommet

Six feet of 10-gauge insulated wire, from battery to relays

Inline fuse holder, 40-amp fuse

Ten feet of vacuum tubing, two Y or T-fittings

European headlight switch panel, Mercedes-Benz part 124 60 03 65

European headlight level control vacuum switch, Mercedes-Benz part 000 800 04 73

Besides normal hand tools, you’ll need a soldering iron and homemade wire hooks to pull out the instrument cluster.

Undoing Things

After disconnecting the battery, remove the old headlights. Behind each side marker assembly, unplug the power socket, release the tab, and push out the assembly. New side markers come with the headlights, but you must switch the old three-pin U.S. socket onto the Euro units, which come with two-prong sockets.

If your car has headlight wipers/washers, this conversion will cost you both, but that’s a small price for More Light. (You can have wipers, but it’ll cost you another $600 for the necessary parts and labor.) Fold down the wiper arms, undo the 8-mm nut, and wiggle the arms off the shafts. Unbolt the two 8-mm nuts holding the metal trim below the headlights, disconnect the washer hose, and remove the trim. Undo the black plastic headlight unit fastener on the sheet metal panel above each headlight. Undo the four 8-mm bolts holding each headlight unit in place. To reach the inside bolt on the left unit, first remove the air intake tube and snorkel. Remove the headlight units, unplug the headlight and wiper motor power cable sockets.

If your car has headlight wipers, the horizontal painted metal trim panels below the lights have holes in them. You can order new, primed panels without holes, part numbers 124 889 05 63 and 124 889 06 63. Have them painted to match or order a spray can of paint in factory color from Tower Paint (800/779-6520) and do it yourself. (The spray can paint is more susceptible to rock chips than properly applied body shop paint, which costs little more.)

Before installing the new bulbs in the headlight assemblies, cut off the small rounded tab on their mounting flange. Keep your fingers off the glass parts of the bulbs, and clean them with alcohol solution before installation. Keep the lower-power bulbs that come with the new headlights as spares. Notice that the new headlight assemblies have a circular vacuum servo to move the headlight reflectors.

Wiring Tips

We wired the new headlights so that when the low beam is on, the fog lights can be switched on or off; for maximum high-beam output, when the highs are on, the lows and fog lights are on, too. The VW relays, which handle up to 40 amps, are required for the high-amperage bulbs we’re using. Working as remote switches to turn on the low beams and fog lights when high beams are selected, they can be mounted on the left headlight assembly. The relays reduce voltage drop by keeping the power wiring as short as possible.

Check the circuit diagram and terminal numbers on the headlight assembly; terminal numbers are also in the Bosch Automotive Handbook (page 790, 4th edition). Before you cut and solder, understand how the power flows. Solder all wiring connections; as Stu says, "A crimped connection is a mechanical connection; a soldered connection is an electrical connection." With high power in a critical circuit, this is no place for quick and dirty.

Pop the cover off the stock female headlight power sockets, and you’ll see that the gray wire goes to the fog light pin; the yellow goes to the low beam pin, the white to high beams, brown to ground. Identify each of the new headlight unit’s six male pins, and wire the new six-pin female socket accordingly (trim back the shrink tubing). Terminal 58 is unused; it’s for the small round European running light above the main headlight bulb; disconnect that gray wire, and tape up the terminal. (In the U.S., the side marker light serves this purpose; that’s why it has three pins instead of two on European cars.)

High-beam power will control the low-beam and fog light relays, so cut the white wire and, using a soldered-on butt connector, add 8-10 in of 14-ga wire with a 2-in jumper on the end to go from terminal 86 on one relay to the same terminal on the other. Before installing the terminals, slip heat shrink tubing onto the wires; heat it with a heat gun or a match held some distance away.

Slot the two relay holders together; mount them on the back lid of the left headlight unit so they face upward with the terminals down (to keep out water and crud). Work out the best spot and check clearance; the air-conditioner receiver/drier is close, as is the self-leveling hydraulic reservoir on wagons. Drill two mounting holes in the cover, and bolt on the relay holders. To keep out water, drill and grommet a third hole, for the wires, on a downward-facing surface of the headlight cover.

To power the whole shebang, run a new 10-ga wire from the battery’s positive terminal to the left headlight. Route it under the cowl air intake, and install the 40-amp inline fuse holder next to the battery. The ground wire from the left headlight can be connected to the existing ground connection behind the unit–or to any other convenient ground.

Installation

Remove the black outer gaskets from the stock headlight units; avoid yanking off their mounting tabs. Install the gaskets on the new headlight units. Transfer the three nut clips from the old units to the new. Attach the ground wire, then slide in the new left headlight unit. Be sure the hood release cable doesn’t bind, and see that clearance exists behind the relays. As you tighten the three mounting bolts, line up the headlight face with the fender. Replace the air intake snorkel and flex pipe.

Slide in the new side marker units; plug in their power sockets and the six-pin headlight power sockets. The windshield wiper power socket remains unplugged, as do the headlight washer hoses; to avoid wasting washer fluid, disconnect the power socket of the headlight washer pump on the fluid reservoir behind the right headlight.

Headlight Level Control Now we’ll install the tubing and dash switch for the vacuum-powered headlight-leveling system. First, use a short piece of rubber hose to connect the vacuum line to the plug on the back of the right headlight. Run the hard vacuum tubing under the fender joint back to the battery then beneath the cowl air intake over to the brake booster area. Run a similar line from the back of the left headlight to the brake booster area; join them with a Y or T-fitting. Now to get the vacuum line through the firewall. Under the cowl, on the firewall just right of the brake booster is a rubber grommet with several lines through it. Using needle-nose pliers, carefully pull out one of the unused nipples, then feed a length of vacuum tubing from the Y through the nipple. Inside the car, pull the headlight knob off its shaft, and undo the 24-mm nut holding the panel; wiggle out the panel, left side first. The vacuum lines will run behind the instrument cluster, so you need to get in there. Pull up the floor mat behind the brake pedal, and unclip the speedometer cable clamp so it can move. Slip the wire hooks in on each side of the cluster, and ease it part way out, right side first. Unscrew the speedometer cable connection, and unplug everything else. Remove the cluster entirely, then reach in (right of the speedo cable) with long pliers to pull through the new vacuum line. This line must be long enough to reach the new level control switch near the headlight switch. Your vacuum source will be the economy gauge line, which you pulled off the back of the instrument cluster. Install a tee in that line and run the new line to the level control switch, with a check valve to allow the vacuum to work but to prevent backflow; the black side of the check valve must be toward the vacuum source (suck it and see). If your car has no economy gauge, use another convenient vacuum source. The "light-out" warning lamp is part of the price of this improvement; the more powerful bulbs confuse the system enough to light that lamp, so you need to disable it. Looking at the instrument cluster face, determine which lamp this is, then go to the numbered sockets at the back (number 5 on ours) and remove the bulb. Reinstall the connectors and the speedometer cable behind the instrument cluster, and slide it back into place. Push the level control into the switch panel, and install the vacuum source hose to the top connector (number 1) and the line to the headlights on the bottom connector (number 2). Reinstall the switch panel, the 24-mm nut, and the headlight switch knob.

Fire ‘Em Up

Reconnect the battery, start the engine, and turn on the lights! If things don’t work, re-check your wiring. Aim the headlights using the three black 13-mm aiming screws behind each unit. The outside screw controls left/right aim, the center one controls height, and the inner one controls fog light height. Setting the headlight level switch to 1 as normal allows 0 as a high position and 2 and 3 as low positions for loads. If your car has self-leveling rear suspension, you might use the 2 slot as normal. If the level control switch doesn’t work, you may have reversed the vacuum connections to it, or you may have a vacuum leak in the new tubing.

You’ll find the light output amazing. Our light meter measured high-beam output four times the stock level! The low beams have better spread and output. The high beams may not look as powerful as they actually are; the fog lights come on with the high beams, and their lenses splash light downward, close to the car, masking long-range improvement. That can be solved by switching lenses. The 300E/400E fog light lens aims light downward. The 500E used a driving light lens to direct light farther ahead. Both can be ordered from U.S. sources. We started with the fog light set-up but switched to the driving light lens.

This $900 conversion was worth it. Doing it yourself can save on labor but requires about a day. You can also offset the cost by flogging your stock lights via a Trading Post ad. Let there be light!

The usual disclaimer applies about violating various local, state, and federal laws, most of which were written back in the "dark ages."

photo credit: Max Scheinwerfer