How to Adjust Headlights on a 2003 F150. Here's your classic good-news-bad-news situation. Bad news first: Ford, in its infinite wisdom, placed the 10th-generation F-150's headlight adjusters well down behind the radiator core support. So, you have to remove the headlight housing to adjust the headlights, and then adjust them by trial and error. The good news, though, is that Ford also made the headlight housings very easy to remove, and you'll probably never have to adjust them unless you replace the headlight housing or something breaks.
Check that your tires are properly inflated, the gas tank is half full, and wait until the late afternoon or early evening when it's somewhat dim out. If you've got the optional self-leveling air suspension, then make sure that the switch is in the "On" position. Park your truck on level ground, facing a white wall 25 feet from your front bumper. Measure up from the ground to the center of the headlight bulb.
Transfer this measurement to the wall, and mark it in four to five places. Run a length of masking tape over the marks -- at least the entire width of the truck -- to give yourself a horizon line. Stand behind the truck and sight along the side of the body. Instruct your assistant to place a mark on the wall that lines up with the side of the truck, then place vertical strip of masking tape to mark it.
Measure in from the side of the truck to the center of the headlight bulb. Transfer that measurement inward from the vertical strips you just place. Place another vertical strip over your horizon line to create a set of crosshairs on the wall. These crosshairs represent the center aiming point of your headlights.
Turn your low beams on to check for proper alignment, and note any discrepancies. The high-intensity zones on the lights should be centered exactly on the vertical crosshair stripe, and the top edge should be either even with or just below the horizon line. If you have two distinct, round light zones, then you have VOL-type or SAE headlights. If the light zones make a continuous horizontal bar, then you have VOR-type lights. VOL or SAE lights should have the top edge of the high-intensity zone 2 inches below the horizon line, while the top edge on VOR lights should be even with the line.
Turn your headlights off. Locate the two tabs recessed into the top of the radiator support, just over the headlight. Hook your finger under the tab, pull up and forward, push the tab back and pull up again. Repeat with the other tab, and you've released the headlight housing from the truck.
Remove the corner parking light to make the process easier. You need only remove the light's Torx-bit fastener -- accessible from the top -- and pull the corner light out. This step isn't strictly necessary, but it will help you get the light out and realign the adjusters when you install it. Once you have the corner lights out, pull the headlight housing forward and out.
Look at the back of the headlight; you'll see three stud mounts on the back of the light -- two on the outer edge, and a third on the lower-inner corner. On each stud is a black, screw-type adjuster with star-shaped thumb tabs on it.
Turn the inner-corner screw clockwise to pull the light in toward the center of the truck; note that it will also pull the beam down slightly. Turn it counterclockwise to push the beam out and up. Turn the outer-upper adjuster clockwise to pull the beam up and outward, and counterclockwise to push it down and in. Turn the lower-outer adjuster clockwise to pull the beam down and to the left, counterclockwise to push it up and to the right.
Turn both of the outer adjusters by the same number of turns to send the beam either almost straight left or right. Turn the inner and bottom-outer adjusters to move it primarily up and down. Note, again, that the beam may move in unintended directions, and that you'll need to play with the third to get it right. Make your first round of adjustments, but don't adjust more than two screws per round of adjustment.
Set the adjusters so that the open portion of the "star" is facing up -- they have to fit in a groove in the truck-side mount. This groove is what keeps the adjusters in place so you'll probably never have to go through this again. Push the headlight back into the truck, being careful to guide the adjustment studs back into their respective holes. Lock the headlight down by pushing down on the tabs, and turn the headlights on to test them.
Repeat the removal and adjustment steps as necessary until the headlight beams are centered where you want them. Don't be surprised if you wind up removing and adjusting each headlight a half-dozen times before settling on an adjustment. It's not unusual for a DIY mechanic to spend half an hour or more on each headlight. When you do finally get sick of messing with them, push the corner-light housing back in and use the last bit of your patience to reinstall its Torx-head fastener.