Here are some possibilities:
* Headlight Switch: A faulty switch can cause intermittent problems. The switch itself might have worn contacts or internal issues.
* Wiring Harness: Corrosion, chafing, or broken wires in the harness leading to the headlights are very common culprits. This is especially true in older cars where the wiring is exposed to the elements. Look for any points where the wiring might be pinched or rubbed against metal parts.
* Connectors: Corrosion or loose connections at any point in the headlight circuit can interrupt the power flow. Check the connectors at the headlight switch, the relay, the headlights themselves, and any junction points.
* Headlight Relay(s): The '85 Corvette likely uses relays for the headlights (probably one for each side, or possibly a single relay controlling both). A failing relay will cause intermittent or complete failure. These are relatively inexpensive to replace.
* Fuse(s): While a blown fuse would cause a complete failure, a partially blown or intermittently failing fuse could cause the intermittent problem you are seeing.
* Grounding Issues: Poor grounding can cause all sorts of electrical problems. Check the grounding points for the headlight circuit. Corrosion can be a major factor here.
* Headlight Bulbs: While less likely to cause *intermittent* failure, a bulb nearing the end of its life can sometimes flicker or fail intermittently before completely dying.
* Body Control Module (BCM): On some models (depending on options), a BCM might be involved in the headlight circuit. A faulty BCM could cause intermittent issues in various electrical systems, including the headlights. This is less likely but possible.
Troubleshooting Steps:
1. Check the fuses: This is the easiest first step.
2. Inspect the wiring harness: Look for any visible damage, corrosion, or loose connections.
3. Test the headlight switch: This might require a multimeter to check for continuity.
4. Replace the headlight relay(s): These are relatively inexpensive and easy to replace.
5. Check the grounds: Clean any corrosion from the ground connections.
6. Check the bulbs: Make sure the bulbs are properly seated and functioning.
7. Inspect the connectors: Look for corrosion or loose connections.
If you're not comfortable working with car electronics, it's best to take your Corvette to a qualified mechanic. Attempting repairs without proper knowledge can lead to further damage. A systematic approach, combined with a wiring diagram for your specific model year, is key to identifying the root cause.
