Swapping Euro style 8" H4 headlamps for the US H5 variety on a late model 928
The Euro H4 headlamps have a more focused beam pattern than the US DOT H5 lamps, with a sharp cutoff at the top (knife-edge). They require more precise aiming to avoid blinding on-coming traffic, but the knife-edge pattern actually makes aiming pretty simple.
In earlier 928s with 7" lights, the H4 swap is essentially a lens and bulb swap, as these cars already have the H4 style plug. In later cars, the situation is not quite as simple.
PARTS NEEDED:
H4 bulb (careful - in the US a modified version of the H4 is sold as 9003 or HB2 and does not provide the H4 beam pattern)
H4 plug (possibly cut from donor car harness)
A complete H4 headlamp assembly sans the cover (bucket) and aluminum U-bracket
Below is item 3, an H4 lamp assembly
H4 Lens housing
Euro metal frame and all attachment hardware (shown assembled on lens housing)
Plastic pivot brackets and nuts (nuts not shown)
Screw clips for cover
The picture above shows the donor items, partially disassembled, except for the pivot bracket nuts, which I did not receive. Also, the plastic pivot brackets are fastened to the pivot posts with press-on speednuts, not pictured, and the cover screw clips are shown lying free. All parts can come from a Euro donor car, or you can buy the parts from US vendors (see next paragraph). Mine came from an 86MY Euro car. It appears that all MYs after 85 are the same...perhaps even earlier. What you need is a complete H4 headlamp, excepting the cover and the aluminum U-bracket that holds it to the mounting base. It's best the get the headlamp assembled as a unit from a Euro donor car - there is NO need to disassemble anything from the donor. Just remove the headlamp cover, and remove the 2 nuts that hold the headlamp assembly to the aluminum U-bracket. All that you need that isn't provided by the donor, unless you cut the wiring harness, is an H4 plug that you can splice into your wiring harness. I got an H4 plug from the local auto parts store that cost me $2.09. You'll need two, of course.
928 International sells new Euro H4 headlamps for $295 each (as of 08/24/07), and from what they show in a picture of the item, it appears you get all the parts you need (except the H4 plug). They appear to be 8" lamps, although this is not stated. 928 Specialists sells the 8" Euro H4 lamp assemblies for $269 (as of 08/24/07). They do not show the components, but it appears to be a complete from the description.
The Euro assembly differs from the US in a few ways:
The Euro lens housing does not have tabs for the headlight cover screws. They are on the metal frame instead. The screws attach to clips slipped on to the frame (as shown in the left picture below)
The Euro frame has a pivot shaft that allows the headlight frame to move after assembly. The US frame screws rigidly onto the aluminum U-bracket.
The Euro assembly has a motor attached to the bottom of the aluminum U-bracket that is activated by an interior switch to allow vertical adjustment on the fly to compensate for load changes. Hence the pivot shaft mentioned above. I did NOT install the motor. This would have required removal of the wheel well covers to access the underside of the bracket, and I did not have the interior switch or wiring. The H4 assembly will work just fine without the motor.
Note the H4 bulb and plug only has 3 prongs, but the Euro H4 housing has 4 prongs. No worries - this is inconsequential. (rightmost picture below). The H5 prong pattern and plug is completely different.
SWAPPING
THE HEADLAMPS:
Here are the steps to the process,
starting with the obvious:
Click on links for pictures..
Turn the ignition to the power on position
Turn on the headlights
Turn off the ignition
Turn off the headlights - they should remain up. I understand in some later models they may retract unless you leave switch in the parking lamps position.
Open the hood and raise it (gives better access to the inner screw on the headlight cover)
Remove the headlight cover (3 Philips screws)
Unplug the bulb
Put a cloth under the front of the headlight lens to protect the paint
Remove the 4 screws that hold the lens assembly to the aluminum U-bracket - allow the lens assembly to lean forward on the cloth
Using a screwdriver pry the locking collar off the lower ball joint attachment
Pry the lower lens assembly socket off the ball joint
Place the US H5 assembly aside
Position the H4 lens assembly so you can pop the lower socket onto the ball joint
Using a screwdriver and (small) fingers, wiggle the locking collar into place
Attach the pivot brackets to the frame pivots and put the bolt ends through the aluminum U-bracket. Affix with nuts. I used nylon locking nuts.
Splice the H4 plug into the wiring harness. I cut off the H5 plug with a couple of inches of lead, saved for future use) and soldered on the H4 to the harness, covering the joints with heat shrink tube.
The H4 plug has 3 prongs while the Euro H4 housing has 4 prongs. No problem for me, although the 4th prong may obstruct some H4 plugs and need to be bent over. H4 sockets do not have a protective boot.
Aim the headlights (see details below).
Install the covers. To get the correct alignment (see "Aiming the Headlights") required using almost all of the screw adjustment, which moves the lamp forward. When you install the cover, there are two little tangs on the lower part of the lens hosing which fit into slots on the cover to help hold it flush. It may be hard to engage them with the lens housing this far forward. Why is the lens housing so far forward? Probably because the Euro motor shaft is shorter than the fixed shaft on the US bracket assembly and I chose not to install the Euro motor, necessitating everything to be positioned more forward.
AIMING THE
HEADLIGHTS:
Thanks to Rich Andrade from the Rennlist 928 mailist who provided the aiming
information. Rich recently did the H5 to H4 conversion on his 93 GTS.
Measure the vertical distance from the center of the headlamps to the ground (30.5 inches in my case)
Measure the horizontal distance between the right and left headlamp centers (45 inches in my case)
Find wall with at least 40 feet of level space in front of it.
Tape a piece of paper to the wall at the approximate height of one of the headlamps. Mark the exact height with a horizontal line using a black marking pen. Measure down 3" and put another horizontal line.
Put a vertical line crossing both lines. This will indicate the lamp center on that side.
Tape the other piece of paper at the same height and so that its center is approximately the same as the headlight centers. Mark the lamp center height with a horizontal line, and place another line 3 inches below that, as you did on the first piece of paper.
Place a vertical line on the second piece of paper at the same distance as the headlight centers. Confused? A couple of pictures are worth thousands of words - see below.
Pull the car up to the wall with the headlights on (low beams) and line up directly in front of the papers.
Back away from the wall as straight as possible so the front of the car is 25 feet away from the wall.
Adjust the headlight so the top of the knife-edge pattern sits on the lower horizontal line (3 inches below dead level). The H4 lights have an edge flare to the beam, so the knife edge angles up on the right side of each beam. You want the edge incline to start at the center mark as shown on the left pattern (E-code) in the picture below:
E-code pattern on the left in
the picture above
Here's my "elegant" aiming apparatus. OK, so it is obvious I didn't use a straightedge to draw the lines. Close enough. The picture below shows the lights on aimed at the targets. The knife-edge pattern is obvious at night, but even in daylight you should be able to make out a faint knife edge lining up with the lower horizontal line with the edge incline starting at the vertical centerline of each lamp.
That's all there is to it.
EXTRA
ADDED ATTRACTION!!
For those that have suffered through my compulsive-obsessive,
step-by-step guide to a relatively simple job, I have a little bonus. Take
a look at the shot below of the middle stall of our garage and try to figure out
how it was made. Click the thumbnail for a larger view. Interesting,
eh?
How did this happen? Full story here...
