The headlight relay is a simple coil that closes the circuit between your headlights and the power source. The headlight relay on a 1998 Cadillac Deville is located inside the relay center on the driver's side of the engine compartment. Checking the relay is a simple process that requires another person to switch the headlights on and off while you inspect the relay. The entire process takes only a few minutes.
Turn off the Deville's engine and remove the keys from the ignition. Open the hood and locate the relay center behind the battery.
Remove the cover from the relay center and locate the headlamp relay. The headlamp relay has the word "Lamp" printed below it.
Test the relay by having someone switch the headlights on and off. If the relay makes a clicking noise, the relay is functioning. If the headlights are still malfunctioning, then there may be a problem with the fuse.
Place the cover back onto the relay center and remove the cover from the fuse block. Locate the headlamp fuse labeled "Head Lmp." If the metal inside of the fuse is broken, the fuse is dead and will need to be replaced.
Place the cover back onto the fuse block and close the hood.
