Where is the horn relay on a car?
In most passenger cars, the horn relay is located in the engine bay fuse/relay box and is labeled HORN. Some models place a separate horn relay in an under-dash fuse box or near the steering column. Knowing where to look can save time when diagnosing a non-working horn.
The horn relay is a 12-volt electro-mechanical switch that powers the horn when you press the horn button. If the horn sounds intermittently or not at all, the relay could be faulty, or the horn fuse, wiring, or horn itself could be at fault. This guide explains where to find the relay and how to test it.
Common locations to check
These are the most frequent spots where a horn relay appears in modern vehicles. Always verify with the vehicle’s fuse diagram or owner's manual, as layouts can vary by make and model.
- Engine bay fuse/relay box: typically near the battery, fender area, or firewall. Look for a relay labeled HORN or HORN RELAY on the box lid or in the diagram.
- Under-dash fuse box (driver’s side): a secondary panel beneath the steering column that often contains the horn relay; check the lid diagram for HORN.
- Near the actual horn assembly: on some older or specialty vehicles, the relay is mounted directly to or beside the horn itself, rather than in a central fuse box.
- Other locations: a few makes place the horn relay in a secondary relay box in the engine bay or inside the passenger kick panel; always confirm with the vehicle’s schematic.
If you locate a relay labeled HORN or see a diagram pointing to a relay function labeled for the horn, you’ve found the horn relay. For ambiguous cases, consult the owner’s manual or a repair guide for your specific model.
How to identify and test the horn relay
To confirm the horn relay is functioning, follow these steps. This list helps you verify the relay’s operation without replacing parts unnecessarily.
- Inspect fuses: locate the horn fuse and the relay’s fuse; a blown fuse will prevent the horn from sounding. Replace with the correct amperage if needed.
- Find and inspect the relay: locate the horn relay, then remove it (with the ignition off and the battery disconnected for safety). Look for signs of damage, corrosion, or a burnt smell.
- Test with a known-good relay: if you have a spare relay of the same type and rating, swap it with the horn relay to see if the horn activates. If it works with the spare, the original relay is faulty.
- Electrical testing: using a multimeter, test the relay coil pins for the expected resistance. With 12V applied to the coil, verify that the output pins switch voltage to the horn when the horn switch is pressed, or perform a swap-test to confirm operation.
- Direct horn test: as a final check, apply 12V directly to the horn (bypassing the relay) using a proper fuse and ground. If the horn sounds, the issue lies in wiring or the horn itself; if not, the horn may be defective.
Different vehicles use four- or five-pin relays with varying coil resistances, so follow model-specific specs when testing or replacing.
Practical notes and safety
Always disconnect the battery before removing electrical components to avoid shorts. If you’re uncomfortable reading electrical diagrams or using a multimeter, seek professional assistance.
Summary
The horn relay is usually found in the engine bay's fuse/relay box and is labeled HORN, though some cars place it under the dash or near the horn itself. To diagnose a non-working horn, check the relevant fuse, locate and test or swap the horn relay, inspect wiring, and test the horn directly. When in doubt, consult your owner’s manual or a repair guide for your specific vehicle model.
