Symptoms
- Audible click from the relay when switching on headlights
- No light output from either headlight
- Other lights (taillights, dash) work normally
- Issue affects both headlights simultaneously
Likely causes
- CommonFailed relay with worn internal contactsA relay can click (mechanical action) while its internal contacts no longer conduct power properly.
- CommonBlown headlight fuse downstream of the relayThe relay can function correctly while a separate fuse blocks power from reaching the headlights.
- PossibleCorroded or damaged wiring between relay and headlightsPhysical damage along the path can prevent power delivery even with a working relay.
- Less commonBoth headlight bulbs failed simultaneously (uncommon but possible)Coincidental failure of both bulbs at once is less likely but should be ruled out.
What to do
- Check the fuse box for a blown headlight fuse and replace with the correct amperage.
- Swap the headlight relay with an identical relay from another circuit to test if the fault follows the relay.
- Check both headlight bulbs individually to rule out a coincidental dual bulb failure.
- Use a test light or multimeter at the connector to check if power is reaching the bulb socket.
- Inspect wiring between the relay and headlights for any visible damage or corrosion.
- Avoid assuming the relay is fine just because it clicks, since a click only confirms mechanical movement, not electrical function.
- Replace the relay if swapping confirms it as the faulty component.
- Have a shop trace wiring if a new relay and good fuses still don't restore headlight function.
Tools and parts
- Fuse puller or pliers
- Test light or multimeter
Headlight relaySearch: “headlight relay for [your car make model year]”
When to call a pro
If a relay swap and fuse check don't solve it, a shop can use a test light to trace exactly where the power is being lost along the circuit.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.