The Volvo P1 (C30, S40, V50, C70) headlights can be tricky to adjust, especially on older vehicles where the brittle plastic mechanism is very fragile.
The height adjustment is on the side (closest to the other lamp) of the headlight – yours may be under a plastic cap if you’ve never adjusted them before. There is a small service port to get at it them through the frame, though the only way I could adjust it in the car is with 12″ of 1/4″ socket extensions and a 1/4″ -> 6mm hex socket. try to apply downward pressure while adjusting to seat the bevel gears together. Adjustment range is about + 6 feet up or down at 20 feet back.
If your gear “clicks” when adjusting this way even after you have lubed it, there is a backup allan (hex) molded directly into the worm gear 90 degrees from the yellow nipple visible from the top. This is very hard to get at when the lights are installed, and using a ball-end hex will likely strip them out. In this case, it’s best to remove-adjust-install-verify in small increments, which is obviously more annoying than the top-adjustment.
If you’ve stripped the allen socket and the bevel gears (which is pretty common, especially if you skip the silicone), check out this swedespeed thread on repairing the mechanism.
The objective of headlight adjustment is to ensure a drop of 3 inches per 25 feet, with a slight 1 inch per 25 foot rightward (LHD) center point. The procedure is pretty simple.
- 2″ wide painters/masking tape (or duct tape)
- a permanent marker
- 25 foot (8.3m) tape measure.
First, find a wall next to a level paved area (back of shopping centers usually are usually suitable) and head there at dusk or at night. BringWith your headlights on, pull the car up square up to the wall until the front plate is just about touching.
Next, put a vertical strip of tape about 6″ high on the wall, passing through each headlight spot, and using your marker, draw a + through the brightest point (points “C”).
Then, measure 25′ (8.3m) back from the wall, ensuring that the tape runs perpendicular to the wall along the front and back tires, and put a piece of tape there on the ground (so you don’t run over the tape measure!). Roll the car back the 25′ until the front plate is just over the 25′ mark.
Now walk back to the wall, and run a long horizontal piece of tape about 3″ below your + marks, across the vertical pieces (the line marked through point “B” below). From each of your marks, measure 3 inches down, and one inch to the right (for US/LHD) and mark a + at that point (“B”).
Adjust the lights so that the cutoff runs along the horizontal tape, and the step hits the “B” mark.
This is a refinement of the procedure as I described a while ago on swedespeed, and is very quick and easy once you get the hang of it. For more information, the authoritative guide on headlight aiming is on Dan Stern’s lighting website.