Setting headlights is easy, if you have the "cut-off" low beam type of lamp characterized by the H4 Bosch, in either the 7" or the 8" version. You can easily tell if you have this type by parking about 10 yards from a blank (white) wall at night and pointing your lights at the wall. I use the local shopping center parking lot and a handy building wall. If, on low beam, there is a distinct horizontal cut-off, above which there is almost no beam, this will work. Park the car on a level surface and aim it, perpendicularly, at a white wall. Take a heavy towel, or some such thing, and cover one head light. you will note that the light projected shows a horizontal limit left of the center-point and then a rising edge from center-to-right.
The first step is to get behind the car and stand right behind the headlight currently shining. Determine that the point where the horizontal limit of the beam meets the rising portion (the center of the beam) is directly ahead of the light, and not to the left or right.
Then take a measuring tape and measure the distance (height) from the ground, to the center of the headlight lens. This is a bit of a trick with the 928 because the headlight lens is so far back from the bumper, but a level held horizontal to the lens will give you this point. With that number in hand, go to the wall with a long piece of duct tape and lay a horizontal line of tape on the wall at that height. Go to the car and adjust the light so that the horizontal cut-off matches that line of duct-tape.
There you have one headlight aimed straight and horizontal. Repeat this process with the other headlight while covering the first with the towel. Note, that you should end up with the two beam center-points the same distance apart as the headlights, and NOT converging to the same single point on the wall. This will give you two parallel and horizontal headlight beams that shouldn't bother anyone and will give you the best lighting to drive by.
Hope this helps.
Aiming your E-Code headlights
E-code headlamps require a specific visual aiming procedure to ensure correct alignment. The car should have at least 1/2 tank of fuel, weight in the trunk equal to the most frequently carried load (this may be a full trunk, or it may be an empty one, or anything in between), and weight in the driver's seat equivalent to the most frequent driver. All of the tires should be checked when cold to make sure they're at the correct inflation pressure. Jounce each corner of the car firmly (grasp the bumper and push down several times rhythmically) to ensure that the suspension is settled into a normal position.
Locate the car on level ground 7,5 meter (25 feet) away from a vertical wall. The vertical wall should then be marked:
(c) (v) (c)
+ (c) is the axis, or aim-respective center, of each headlamp. This is usually indicated by a name brand or another mark on the headlamp lens.
If no mark is present, make a careful estimate by looking at the bulb location inside the headlamp. The bulb axis is also the headlamp axis.
o (v) is the centerline of the vehicle. Site through the backglass and windshield of the car to aid in placing this mark accurately.
b-b is a line parallel to and 7.5 cm (3 inch) below (c)-(c)
Note that US regulations have recently been modified to permit new cars to be equipped with headlamps very similar to E-code lamps, but with line b-b raised to5 cm (2.1 inch) below c-c. You may wish to experiment with both settings and use the one you feel offers the best performance for your specific driving situation.
+ Draw a vertical line through through the center of each (c) point. Do the same with the o (v) point. You now have an accurate plot on the wall of the locations of the headlamps.
(The (c) and (v) designations are for purposes of clarity in this descriptive article. It is not necessary to draw "(c)" and "(v)" on the wall--just plot the points. Of course, you may use the letters in your aiming procedure if it will help you.)
The upper horizontal edge of the low beam light pattern must be directly on line b-b. This will place the upper horizontal edge of the low beam light pattern 7.5 cm (3 inches) below the centerline of the headlamp at 7.5 meter (25 feet) with ECE-spec aiming, and 5 cm (2.1 inches) below the centerline of the headlamp at 7.5 meter ( 25 feet) with US-spec aiming.
The "break point" or "kink" in the top edge of the low beam light pattern is where the horizontal upper edge of the low beam light pattern begins to rise to the right or steps upwards (see diagram). Adjust the headlamps so that the kink is within +/- 5 cm (2 inches) of point (c).
After adjusting a high/low beam headlamp in the low beam mode, do not attempt to readjust it in high beam mode. All high/low beam headlamps are meant to be adjusted on the low beam setting only--the high beam adjustment is correct when the low beam adjustment is correct.
HIGH-BEAM-ONLY LAMPS IN 4-LAMP SYSTEMS
These must be adjusted so that the bright, center "hot spot" of the beam is straight ahead of the lamp in both the vertical and horizontal planes. Use the intersection of the horizontal and vertical lines at points (c) as "cross-hair sights" to center the high beam hot spot.
Make sure to cover the adjacent high/low beam lamp when you are aiming its high-beam-only neighbor.
That's all there is to it!