Simple Checks (Do these first):
* Headlight Switch: The most obvious culprit. Try turning the headlight switch completely off and then back on again. Is it stuck or malfunctioning? A loose connection at the switch itself is also possible.
* Fuses: Check the fuses related to the headlights in the fuse box (usually under the hood and/or inside the car). Look for blown fuses (a broken filament inside). Replace any blown fuses with the correct amperage. If a fuse blows immediately after replacement, there's a short circuit somewhere in the system – don't keep replacing it!
* Light Switch Relay: The headlight switch often works through a relay. This is a small electrical switch that amplifies the signal from the switch to the headlights. Locate the headlight relay in the fuse box and try swapping it with a similar relay (if possible) to see if that fixes the problem.
* Headlight Bulbs: Though less likely to suddenly fail while driving, it's worth a quick check to make sure both bulbs are still functional. A bulb filament could break, but this usually results in a gradual dimming before complete failure.
More Complex Issues (Requires more mechanical knowledge or a mechanic):
* Wiring Issues: A short circuit, corroded wires, or loose connections in the wiring harness leading to the headlights could interrupt the power supply. This can be difficult to diagnose and may require tracing the wiring.
* Multi-Function Switch (Turn Signal/Wiper Switch): The turn signal and wiper switch often incorporates the headlight switch circuitry. A faulty switch could be the problem.
* Body Control Module (BCM): This module controls many electrical functions, including the headlights. A malfunctioning BCM can cause various electrical issues, including headlight failure. This is more of a last resort diagnosis.
* Alternator/Battery Issues: While less likely to cause the headlights to simply shut off completely, a failing alternator or low battery voltage could cause the headlights to dim significantly or even cut out, especially under higher electrical load (like running the heater or AC). Check your battery voltage with a voltmeter.
* Ignition Switch: A failing ignition switch could affect power to various systems, including the headlights.
Troubleshooting Steps:
1. Start with the simple checks: fuses, bulbs, and the headlight switch itself.
2. Check the relays: this is an easy intermediate step that can often solve the problem.
3. If the problem persists: Consult a wiring diagram for your specific Impala model to trace the headlight circuit. You may need a multimeter to check for voltage and continuity in different parts of the circuit.
4. If you're not comfortable with electrical work: Take your Impala to a qualified mechanic for diagnosis and repair. Trying to troubleshoot complex electrical issues without the right knowledge and tools can be dangerous.
Remember safety first! Driving at night without headlights is extremely dangerous. If your headlights go out, pull over to a safe location as soon as possible.
