1. Check the Bulbs:
* Burned out bulbs: This is the most common cause. Replace them with the correct type (refer to your owner's manual or a parts store). Make sure to disconnect the battery negative terminal before handling bulbs to prevent electrical shock.
* Loose bulbs: Even if not burned out, a loose bulb may make poor contact and result in dim or intermittent headlights. Ensure they're firmly seated in their sockets.
2. Inspect the Wiring and Connectors:
* Corrosion: Look for corrosion on the bulb connectors, wiring harnesses, and the headlight switch. Clean any corrosion with a wire brush and electrical contact cleaner.
* Broken wires: Check the wiring for any breaks or frays, particularly near the headlight units and the connectors. Repair or replace damaged wiring.
* Headlight switch: A faulty switch can prevent power from reaching the headlights. Testing the switch's continuity with a multimeter might be necessary (this requires some electrical knowledge).
3. Relays and Fuses:
* Blown fuses: Check the fuse box (usually under the hood or inside the car) for blown fuses related to the headlights. Replace with the correct amperage fuse.
* Faulty relays: Headlight circuits often use relays. A bad relay can prevent the headlights from working. Try swapping the headlight relay with a known good one (if you have a spare or can borrow one) to see if that solves the problem.
4. Headlight Switch:
* If you have tested everything else and the headlights still don't work, the headlight switch itself might be faulty. These can be relatively expensive to replace and are better diagnosed with a multimeter.
ONLY AFTER you've ruled out all the above, should you consider headlight aiming adjustment:
Adjusting Headlight Aim (if bulbs and electrical system are functioning):
1. Park on a level surface: Ideally, against a wall or garage door about 25 feet away.
2. Mark the center of each headlight: Use masking tape.
3. Measure the headlight height: Measure from the ground to the center of each headlight. This will help you return to the original position if needed.
4. Locate the adjustment screws: These are usually located on the back of the headlight housing. You'll typically find two screws: one for vertical adjustment and one for horizontal. They are often small Phillips head screws.
5. Adjust the headlights: Turn the screws to adjust the beam's height and horizontal position. Refer to your owner's manual for the specific instructions and recommended aim settings. Generally, you want the headlights aimed slightly downward to avoid blinding oncoming drivers.
6. Check the aim: After making adjustments, check the beam pattern on the wall or garage door. The cutoff line should be relatively straight and even. Adjust as needed until you achieve proper aim.
7. Re-check after driving: After driving for a short while, recheck the aim. The suspension settles and this can slightly alter the aim.
Important Notes:
* Owner's Manual: Consult your 1990 Corvette owner's manual for specific instructions and diagrams related to headlight adjustment and troubleshooting.
* Professional Help: If you're not comfortable working with car electrical systems, it's best to take your Corvette to a qualified mechanic. Improper wiring repairs can cause further damage or even create a fire hazard.
Remember safety first! Always disconnect the battery negative terminal before working on the electrical system. If you are unsure about any step, seek professional assistance.
