* Headlight Switch: This is the most frequent cause. The switch might be failing internally. It might be stuck in a position where it doesn't complete the circuit for low beams, even though it's working for other functions (parking lights, brights). Testing the switch's continuity with a multimeter is the best way to diagnose this.
* Headlight Relay: Many vehicles use relays to control the high current draw of headlights. A failed relay will prevent the headlights from turning on. You can usually find the relay in the fuse box (under the hood or inside the car, depending on your Skylark's model). Visually inspect it for damage and try swapping it with a known good relay of the same type (if you have a spare or can borrow one).
* Wiring Issues: A broken wire, corroded connection, or loose terminal in the headlight circuit between the switch and the headlights themselves is a strong possibility. Inspect the wires leading from the headlight switch to the headlights for any damage, especially where they might rub against the chassis or other components. Pay close attention to connectors and grounds.
* Blown Fuse (less likely): While you'd expect all lights to be out with a blown fuse, sometimes only a portion of the lighting system is on a specific fuse. Check your fuse box for a fuse specifically related to the headlights (consult your owner's manual).
* Multi-Function Switch (sometimes called the turn signal switch): While less common, a failing multifunction switch can sometimes selectively disable certain functions, even if others work.
Troubleshooting Steps:
1. Check the Fuses: Start with the simplest check. Look for a blown fuse related to the headlights.
2. Inspect the Headlight Switch: If possible, try wiggling the headlight switch while someone tries to turn on the headlights. A clicking sound or change in behavior might indicate a problem.
3. Relay Check (if applicable): Locate the headlight relay and inspect it or swap it out.
4. Visual Wire Inspection: Carefully examine the wiring harness leading from the switch to the headlights, looking for breaks, corrosion, or loose connections.
5. Ground Connections: Check the ground connections for the headlights. A poor ground can prevent the lights from working properly. Clean and tighten any connections you find.
6. Multimeter Testing: This is the most effective method for pinpointing the problem. A multimeter can test the continuity of wires, the functionality of the switch, and the operation of the relay. You'll need a wiring diagram for your specific Skylark model to do this correctly.
If you're not comfortable with electrical work, it's best to take your Skylark to a qualified mechanic. Attempting to diagnose this without a wiring diagram and a basic understanding of automotive electrical systems can lead to further damage.
