* Blown Headlight Bulbs: This is the most common cause. Check both headlight bulbs to ensure they're not burnt out. It's possible one or both have failed.
* Headlight Switch: The headlight switch itself might be faulty. It could be internally broken or not making proper contact.
* Wiring Issues: A break or short in the wiring leading to the headlights is another possibility. This could be anywhere from the switch to the bulbs themselves. Corrosion in the connectors is a frequent culprit.
* Fuses: Check the fuse box for blown fuses related to the headlights. Your owner's manual will show you which fuses control the headlights.
* Relay: Headlights often use a relay to switch the high current needed. A faulty relay can prevent the headlights from working.
* Multi-Function Switch (Turn Signal/Headlight Switch): A problem with this switch could affect both the headlights and turn signals.
* Headlight Dimmer Switch (if equipped): If your DeVille has a dimmer switch, it might be malfunctioning.
* Ground Issues: A poor ground connection can prevent the headlights from receiving the necessary power.
Troubleshooting Steps:
1. Check the Bulbs: This is the easiest and first thing to do.
2. Check the Fuses: Locate the headlight fuses in your fuse box and check for blown fuses.
3. Inspect the Wiring: Look for any visible damage or corrosion in the wiring harness leading to the headlights.
4. Test the Headlight Switch: If possible, try bypassing the switch temporarily (this requires some electrical knowledge and caution).
5. Check the Relay: Locate and examine the headlight relay. You might need to test it with a multimeter.
6. Check the Ground: Make sure the ground connection for the headlights is clean and secure.
If you're not comfortable working with car electrical systems, it's best to take your Cadillac to a qualified mechanic for diagnosis and repair. Attempting repairs without proper knowledge can be dangerous.
