Replacing a burned-out lamp. When a single headlight fails, the likely cause is a burned-out filament. Testing and replacing conventional headlamps requires only screwdrivers and a jumper wire-a length of wire with an alligator clip at each end.
Remove the cover molding, held by screws; for a late-model General Motors car you’ll need a Torx-head screwdriver, available in auto parts stores.
Next remove the screws that hold the bezel-the metal ring that holds the headlamp to its housing. Don’t touch the spring-loaded screws that control headlamp aim, or you’ll disturb this adjustment. If the bezel screws are rusted in place, spray them with penetrating solvent, allowing 10 to 15 minutes for the solvent to work.
Pull the headlamp forward to unplug its wire connector. Connect the jumper wire to either battery terminal, and hold one terminal of the headlamp against the other battery terminal. Touch the open end of the jumper wire to the other headlamp terminal(s) one at a time. The headlamp should light if it is good. In that case, check the terminals on the headlamp and wiring connector for corrosion; wire-brush them clean.
A replacement headlamp should be of exactly the same size and type (not necessarily the same brand) as the one you are replacing. If you have halogen lamps, don’t install a standard lamp. Be careful to install the headlamp right side up with its locating lugs lined up with the housing.
Some cars have so-called aerodynamic headlamps, which contain replaceable halogen bulbs. These come out from the rear of the housing and are accessible with the hood up. Handle the bulb carefully, only by its plastic base. Follow replacement instructions in the owner’s manual.