You can adjust the headlights on your Mazda 3 by using the 10mm adjustment bolt on the backside of the headlight housing assembly. This bolt will allow the only adjustment available on the Mazda 3. Adjusting your Mazda 3's headlights is necessary whenever you replace the housing assembly. If you've never done this job before, it may take you 20 to 30 minutes.
Park your Mazda 3 facing a flat surface such as a wall. Park roughly 20 feet away from the wall.
Turn the headlights on.
Open the hood of the car and locate the adjustment bolt on the back of the headlight housing assembly.
Turn the headlight adjustment bolt until the headlight beam shines at the base of the wall or other flat surface near the ground. Ideally, you want the headlights to shine where the headlight beam meets the ground.