1. Bulbs: This is the most likely cause. Headlight bulbs age and dim over time. They can also simply burn out.
* Check: Inspect your headlight bulbs. Look for any obvious signs of damage, discoloration (blackening), or filaments that are broken. Replace with the correct wattage and type of bulb (refer to your owner's manual).
2. Dirty or Fogged Headlight Lenses: Over time, the plastic lenses can become clouded with dirt, oxidation, or yellowing. This significantly reduces light output.
* Check: Clean the lenses with a dedicated headlight cleaning kit or a mild abrasive cleaner. If heavily oxidized, you may need to polish or even replace the lenses.
3. Low Voltage: A weak battery, corroded battery terminals, or problems with the charging system (alternator) can result in lower voltage, causing dim headlights.
* Check: Test the battery voltage with a multimeter. It should read around 12.6 volts when the car is off and slightly higher (13.5-14.5 volts) when running. Inspect the battery terminals for corrosion and clean them if necessary. If the voltage is consistently low, have your alternator and charging system tested.
4. Wiring Issues: Loose, corroded, or damaged wiring in the headlight circuit can reduce voltage reaching the bulbs.
* Check: This is more involved. You'll need to visually inspect the wiring harness leading to the headlights, looking for any damage or corrosion. A multimeter can be used to check for continuity and voltage at various points in the circuit. This is best left to someone experienced with automotive electrical systems.
5. Headlight Switch: A faulty headlight switch can also restrict power to the headlights.
* Check: This is less common but possible. Replacing the switch is typically an involved job. It might be best to consult a mechanic if you suspect this is the issue.
6. Relay: The headlight circuit uses a relay to switch the high current. A faulty relay can also cause dim or intermittent headlights.
* Check: Locate the headlight relay (usually in the fuse box under the hood or inside the car) and visually inspect it. You can also try swapping it with a known good relay of the same type (if possible).
7. Grounding Issues: A poor ground connection can prevent the headlights from receiving the full voltage.
* Check: Inspect the ground connections for the headlight circuit, ensuring they are clean and secure.
Before you start: Always disconnect the negative terminal of the battery before working on any electrical components in your vehicle. This is a crucial safety precaution. If you're not comfortable working with car electrical systems, it's best to take your Impala to a qualified mechanic.
