Upgrading Your 1965-1989 911 Headlights From Stock H5 To European H4

Today we had a customer come in with his much-beloved and well driven 88' 911 Targa to have some work done. Asides from having us replace his catalytic converter and change his oil (a mechanic at a different shop used an oil with a high zinc content, which is incorrect for the year of his car, which in turn destroyed his original catalytic converter), he had us upgrade his stock H5 headlights to Bosch Euro H4 headlights.

These headlights have seen better days.

Water and dirt were entering through this hole.

His headlights were a little worse for wear. Dirty, scratched, cloudy, cracking, and on the driver's side headlight, a rock kicked up from another car had hit the light, creating a hole, which would allow dirt and water to enter into the housing. On top of that, the amount of light that the H5 bulbs were outputting left a little to be desired.

He wanted a solution for his poorly performing stock lights, and our Bosch European H4 headlights were the answer. The H5 headlight as found on US-market 911's is a sealed unit, with a plastic housing that was prone to melting and damage. The European H4 headlight has a metal housing, and can be disassembled if you need to replace just the lens. The Euro H4 headlight assembly also has superior light output due to it's lens construction.

Bosch European H4 Headlight Assemblies are the popular upgrade from stock USDM H5 lights. 

Fortunately, replacing the tired H5 headlights with the better European H4s is a simple process. If you have a pre-1987 911, all you need is the H4 headlight assembly and an H4 bulb; if you have an 87-89 911, the bulb sockets are different, so you will need either an inexpensive "repair" harness to convert  your wiring to an H4-compatible socket, or make an adapter to bridge between the stock H5 socket and H4 bulb.

This screw is what holds the trim ring in place. Make a note of the angle the screw attaches to the tab inside for when you install the new headlight.

The headlight rings on this car had not been removed in a very long time, so we had to coax it off.

With the trim ring removed, you will have access to the 4 screws that need to be removed to remove the entire headlight assembly.

After the 4 screws are removed, the connector can be removed from the headlight, and the old headlight can be removed completely.

The first step is to remove the trim ring around your H5 headlight. There is only a single screw holding it in place, so with that screw removed, the ring can then be slid off. You may have to "persuade" it a little to come off, depending on how long it's been since it was last removed.
With the ring removed, you can see the 4 screws that attach the headlight retainer to the car. Remove those 4 screws, and the entire headlight assembly can then be removed. Make sure to pull the headlight out enough to be able to detach the headlight from the stock harness before completely removing the headlight.

1987-1989 911's use a different headlight connector than older models, requiring the need to convert to an appropriate connector.

Converting to the correct H4 connector is a simple process. Only 3 wires per side.

Those of you with pre-1987 911's can skip this step, but for those that are left, this is the part where you have to make your stock wiring able to accept the new H4 bulb. If you made yourself an adapter, now is the time to plug it into the stock H5 socket and skip ahead. In our case, we opted to cut off the old socket, and go the repair harness route. With the stock harness, the blue wire is high, yellow wire is low, and brown wire is ground. If you go with this method, ensure that you wire your harness apprpriately.

Of note: the owner had us use Hella 55/60W H4 bulbs for his car, which do not require any upgrades to the stock wiring harness, as they the same wattage as stock. If you want to use a brighter/more powerful bulb, it is highly recommended to use an H4 relay harness to prevent any potential problems that may occurr when using a higher wattage bulb with stock wiring.

Install the new H4 bulb into the H4 assembly, making sure to not touch the glass of the bulb itself (the oils from your skin cause hotspots on the bulb during use, significantly decreasing it's lifespan).

Install the new H4 bulb into the housing, and then attach the headlight connector.

It may take a few tries to get the new headlight aligned in the fender properly. 

 The new headlight assembly only needs to attach to your car via the single screw that held on the stock trim ring that you removed from the first step. Connect the headlight to the harness, and insert it into the fender. There is a lip around the hole in the fender that the headlight will grab onto, and the screw that is on the bottom of the headlight assembly will attach to the tab that the screw from the original trim ring. It may take a few tries to align the H4 headlight screw with the tab on the body, so if it doesn't feel like it's grabbing, take the headlight out and try inserting it in from a slightly different angle. When the headlight assembly is properly aligned and the screw tightened, there should be no movement of the headlight.

Adjust the aim of your new headlights using the two adjustment screws on either light.

Once you have both headlights installed, all that's left to adjust your headlamps so that you get proper coverage when the lights are on. There are two adjustment screws on the other ring that allow you to do it easily.

And that's it. A quick and simple upgrade to your car that will greatly improve your driving safety at night.