What Is a Horn Relay?

A relay operates your car or truck horn.

When you press the horn button on your car or truck, you operate a relay that makes contacts to connect the horn to voltage from battery. Low current through the button controls higher current through the horn itself.

The Relay Coil

Applying voltage to the coil of the horn relay causes it to become an electromagnet. It pulls an internal lever that makes the actual contacts.

The Relay Contacts

Electrical connections to the relay provide voltage to the common (C) pin on the relay, which moves from the normally closed (NC) position to the normally open (NO) position when energized. The NO contact then sends voltage to the horn, causing it to operate.

Replacing the Relay

Horn relays are standard automotive five pin relays that plug into a socket. Check your owner's manual to find your horn relay, usually located under the hood or near your fuse panel. If it's bad, simply pull it out of the socket and replace it with a new one.

References

• 2carpros: How Do I Check a Car Relay
• The12volt: SPDT and SPST Automotive Relays