Back at the dawn of the automobile, motorists used oil- or acetylene-gas-powered headlamps, which generally cast a weak beam of light "somewhere over there." Of course, that was fine, because you could typically say the same of the cars themselves; point them in a given direction, and they would eventually wind up somewhere over there. But a modern automobile like the second-generation S10 would be a supercar by 1900s standards -- so, its headlights require a bit more power, and precision in aiming.
Items you will need
- Grease pen or lipstick
- Measuring tape
- Yard stick
- A white or light-colored wall
- Level parking area
- One-inch painter's masking tape
- Number 15 Torx bit
- Bit driver
Fill your gas tank halfway with fuel to compress the truck's rear springs. Find a white wall with at least 50 feet of level parking area adjacent to it, and park your truck directly facing the wall with the front bumper exactly 25 feet from it. It's important that you park your truck at exactly a 90-degree angle to the wall, so take your time here.
Measure the top edge of your windshield from side to side, and mark the center-top of the windshield with either a grease pen or lipstick. Repeat on the bottom edge of your windshield, and on your rear window. Now, tape a length of painter's marking tape up the center of your windshield over both marks, and repeat on the rear. You now have a vertical center line to align your truck with the wall.
Stand directly behind your truck so that the tape on the front and rear windows are aligned. Have your assistant go to the wall, and give him verbal instructions to place a mark on the wall that aligns directly with the truck's center line. Have him place a few marks from ground level, going up, then go to the wall and run a length of tape vertically up from the ground to cover the reference marks. If you're extremely particular, you can use a string and a plumb bob to find the exact average center of multiple marks and place your length of tape there.
Measure the vertical height from the ground in front of your front bumper to the center of the headlight bulb. A ruler extended out horizontally from the center of the headlight bulb can help here. Transfer that measurement to the vertical tape line on the wall, and to two other points three feet on either side of the vertical line. Now, run a horizontal tape line from mark to mark to give yourself a "horizon" line. Measure the distance straight across from the center line of the grille using your yardstick. Don't use the tape measure -- you'll wind up following the hood and ending up with an artificially long measurement.
Transfer that measurement from the wall's vertical reference line, along the horizon line, and mark the spot where it lands on the horizon line. Place another piece of vertical tape on the horizon line to for a "crosshair" exactly ahead of your headlight bulbs. Pop your hood, and turn your headlights on low beam. The S10 uses a single headlight bucket for both the low- and high-beam lights, so you can only adjust one or the other. The low beams are the more sensitive of the two in terms of adjustment.
Look down at the tops of your headlights. You'll see two Torx-bit adjustment screws; the one closer to the grille adjusts the vertical, and the one on the outer edge -- hidden deep below an access hole in the front support -- adjusts the horizontal. Now, it's just a matter of turning the screws to adjust the lights' zones of highest intensity so that the top-most edge of the high-intensity part of your beam lands on the bottom edge of the horizon tape line. You want the beams pointed slightly downward, so it's appropriate to align just the top edge of the beam with the bottom of the horizon line.
Adjust both headlight's side-to-side orientation so that the left edges of their high-intensity circles land on the vertical line from that light's target. Yes, that's right -- you want both of your lights pointed slightly to the right to avoid blinding oncoming traffic. When you're finished, the lights' high-intensity circles should tuck neatly in the crosshairs' lower right-hand corners without crossing onto the masking tape.
- If you want to be super accurate about your truck's angle to the wall -- which is crucial for left-right targeting -- then you can measure a pair of lines 25 feet outward from the wall to the edges of the truck's front bumper. Of course, that doesn't entirely guarantee accuracy, since those lines also have to come out at a 90-degree angle. For the ultimate in accuracy, use your tape measure to measure from the edges of the truck's front bumper to the first vertical reference line on the wall. When your left and right bumper-to-line cross-measurements match, you're facing the wall at a perfect 90-degree angle.
- ProDemand; 2003 Chevrolet S10; Service Manual; Lighting Systems; Headlamp Aiming Procedure