Replacing a headlight on a Mazda should be done as soon as it burns out. Headlights should be inspected every three to six months to make sure that no damage to the headlight wiring is present and that the headlight is functioning normally. The headlight housing assembly should be in good shape and there should not be an excessive amount of moisture inside the housing. Replacement headlights can be purchased from any auto parts store. You will need the part number that is stamped on the bottom of the old headlight to know what kind of bulb your Mazda takes.
Open the bonnet and remove the retaining clip on the back of the headlight housing assembly. Mazda usually uses a plastic cover and clip to shield the headlight from debris. Pull the clip off and then pull the cover off.
Remove the electrical connector from the back of the headlight ballast.
Turn the headlight counterclockwise and pull it out of the housing assembly.
Align the tabs on the headlight with the notches cut into the housing and insert the new headlight.
Turn the headlight clockwise to lock it into the housing assembly.
Reconnect the electrical connector to the headlight ballast.
For specific information about replacing the headlight in your Mazda, consult the vehicle's manual.