Where is the headlight relay switch located on a 2004 Chevrolet Cavalier?

The headlight relay for a 2004 Chevrolet Cavalier is typically located in the underhood fuse box (also called the Power Distribution Center or PDC). However, there isn't a single "headlight relay switch." Headlights are controlled by a combination of the headlight switch inside the car, fuses, and relays in the fuse box. There may be multiple relays involved, depending on the specific options your Cavalier has (e.g., fog lights).

To find it, you'll need to:

1. Locate the underhood fuse box: This is usually a black plastic box near the battery, often attached to the inner fender. Your owner's manual will show you the exact location.

2. Open the fuse box cover: You'll likely need to unscrew or unclip the cover.

3. Consult the fuse box diagram: This diagram is usually printed on the inside of the fuse box cover. It will show the location of all the fuses and relays and what they control. Look for relays labeled "Headlights," "Parking Lights," or something similar. There might be separate relays for high beams and low beams.

Important Note: Before working on any electrical components, disconnect the negative terminal of your battery to avoid electrical shock or short circuits.