There are four main components to the 1983 Chevy Scottsdale pickup's headlight electrical circuit that allows a headlight to function properly: the headlight bulb; the fuse that operates on the circuit to prevent surges of electricity from damaging the electrical components; the headlight relay that switches the headlights on and off when the headlight switch is turned, and the wiring harness that brings power to the headlight. Any of these components may be the source of difficulties if your headlights are not working.
Turn on your headlights. Replace any that do not turn on. Prop open the hood. Unplug the headlight wiring harness by depressing its side tabs. Pull off the rubber weather shroud on the rear of the headlight assembly. Put on your latex gloves. Press in on the metal retaining clip holding the headlight in place. Pull out the headlight. Insert the replacement. Secure it in place with the metal clip. Replace the rubber shroud. Plug back in the headlight wiring harness. Turn on the headlights again. If any still do not turn on, continue to the next step.
Open the fuse box on the left side of the engine compartment. Pull out the fuse that operates on the circuit with the non-functioning headlight. Replace the fuse if it is blown. Insert the replacement fuse into the empty slot. Turn on the headlights. If any still do not work, continue to the next step.
Inspect the headlight relay in the fuse box. Put your ear near the relay. Have a friend turn on the headlights. If you do not hear a click, replace the relay. Otherwise, pull the relay out of its socket. Test the electrical resistance of the relay coil with the ohmmeter feature on your multimeter. If the meter reads above 100 ohms, replace the relay. If it reads below 100 ohms, check that the voltage on the open contacts of the relay read 12 volts with the voltmeter feature of the multimeter. Replace the relay if it does not read 12 volts. If it does read 12 volts, continue to the next step.
Unplug the headlight wiring harness. Check that the positive lead of the wiring harness has current coming through it, using the voltmeter feature of your multimeter. If the wiring harness does not have power coming through it, replace the wiring harness. Turn the headlights back on and verify that the non-functioning headlight now works.
