In most cars, the headlight relay sits in the engine bay fuse/relay box, but some models place it inside the cabin behind the glovebox. On newer vehicles there may be no separate headlight relay at all, with headlights controlled directly by the lighting switch or a body control module. To know your exact location, check your owner’s manual or the fuse/relay diagrams on the covers.
Common locations
Headlight relays are usually found in one of two places. The following list highlights the spots you should check first.
- Engine compartment fuse/relay box labeled Head Lamp Relay, Low Beam Relay, High Beam Relay, or similar wording.
- Interior fuse panel (often behind the glovebox or under the dash) with a relay labeled Head Lamp or Headlight.
- Some modern vehicles rely on the body control module (BCM) or the lighting switch to control headlights directly, leaving no user-accessible separate relay.
Because labels and layouts vary by make and model, always refer to the diagram on the fuse box cover or the owner's manual for your specific vehicle.
How to identify the exact location for your car
Engine bay vs interior panels
As a rule of thumb, most older and many mid-range cars store the headlight relay in the engine bay, but some models relocate it to an interior fuse box. If you’ve checked the engine bay and don’t see a clearly labeled headlight relay, look inside the cabin fuse panel behind the glovebox or under the driver's side dash.
Check the fuse box cover diagrams
The lid of each fuse/relay box typically has a diagram listing relay names and locations. If the cover is missing or faded, refer to the vehicle’s manual or a dealership diagram for exact labeling.
Steps to locate and verify
Use these steps to locate the headlight relay and determine whether it’s the source of an headlight issue.
- Open the hood and inspect the engine compartment fuse/relay box. Look for a relay labeled Head Lamp Relay, Headlight, Low Beam, or High Beam.
- If you don’t find it in the engine bay, check the interior fuse panel (often behind the glovebox or under the dash) and review its diagram for a headlight relay.
- If you locate a relay with a matching label, you can test it by swapping it with a similar relay in the same box (for example, a horn or turn-signal relay) to see if the headlights respond when the swapped relay is used.
- Replace the relay if swapping resolves the issue, or if the relay is visibly damaged or burnt. If swapping does not fix the issue, inspect related fuses, wiring, the headlight switch, and possibly the vehicle’s lighting control module or BCM.
These steps help determine whether the problem lies with the relay itself or with another electrical component linked to the headlights.
What if you can't find it?
If your vehicle’s manual and diagrams don’t reveal a separate headlight relay, or the relays aren’t labeled in a way you can identify, consult a service manual for your exact make, model, and year, or contact a dealer or qualified mechanic. Some newer cars use centralized lighting control without a user-accessible headlight relay, which can complicate DIY testing.
Summary
Most headlight relays reside in the engine compartment's fuse/relay box, but interior fuse panels behind the glovebox are also common. Some modern vehicles do not use a separate headlight relay at all, relying on the lighting switch or a control module. To locate yours, check the fuse panel diagrams in both locations and reference the owner’s manual. If you suspect a faulty relay, consider swapping with a similar relay to test, and replace the part if the issue follows the swapped relay. When in doubt, a professional can ensure safe and accurate diagnosis.
Does one relay control both headlights?
You will need two. One for the low beams on each headlight and one for the highs. You split the lead that feeds the headlight into 2 leads. One lead to the drivers side headlight and one to the passenger side originating from each beam powers corresponding relay.
How do I tell if I have a bad headlight relay?
Before we move to the fourth. Sign subscribe for more insights on diagnosing electrical issues like this the fourth sign of a bad headlight relay is uneven or dim headlights.
Where is my headlight relay located?
Headlight relays are often in the fuse box.
Which relay controls headlights?
In a typical computer-controlled headlight circuit, two relays—one for the high beams and one for the low beams—control the headlights. Some vehicles also have a third headlight relay to activate the daytime running lights (the dimly lit headlights that automatically come on during the day).