In this article, I’ll explain the wiring diagram of a 3-pin horn relay to simplify the process of wiring the relay on your bike or car.
As an electrician, I have occasionally needed to wire horn relays and learned a few tips. A relay aids in the control of the horn circuit’s power. It facilitates the release of the link that completes the horn circuit, allowing it to complete the circuit and ring when engaged. Knowing how to wire a horn relay will assist you in dealing with the situation of replacing a faulty horn or racing faults in a dysfunctional horn relay.
A relay is an electrical switch consisting of an input terminal or pins for single or multiple control systems and an operating contact terminal. The switch may have indefinite contacts in various forms. On a 3-pin relay, the center (pin 2) pin connects to the battery’s positive terminal while the third and first pins connect to the negative post (on a 12v battery) and the horns in a particular order.
I will go into detail in this guide.
The 3-Pin Horn Relay Wiring Diagram
Terminal or Pin 1 and 3
Clip a brown wire to the ground and connect it to the third terminal on the 3-pin relay. Connect another wire from the negative wire to one terminal on the horn. Connect the other terminal of the horn to pin 1 on the relay unit.
Note: Horns don’t have polarity, so it doesn’t matter which wire goes where when splitting the negative connection to link to the horns.
Terminal or Pin 2 (At the Center or Mid Position)
This terminal connects to the wire containing the volts or power — the hot wire that attaches to the positive terminal on the battery.
You may use a blue or red wire (standard color code for hot wires) to connect the relay’s middle terminal containing (shown in the diagram below). You can strip the wire to about 1 inch deep to expose the conductive threads or surface.
Importance of Using a Relay in Horn Connections
To produce enough sound a vehicle or bike’s horn uses a significant amount of current. A horn circuit threads up the steering column on early vehicles, and it was not rare for the ‘Push Switch’ on the column to weld closed because it was not pushed hard enough. Furthermore, carrying the high current required fairly heavy wire, which was also a fire hazard.
The inclusion of a relay eliminated the high current running up the steering column, allowing for much quicker switching and the control of two or more horns.
Frequently Asked Questions – FAQs
Is a Horn Relay a Must?
Relays are used to allow a lower power circuit to control a higher power circuit.
The cables and sprung switch contacts in the steering column are low power in the horn circuit, while the horn itself consumes more power. The relay input is controlled with little power, but the output contacts can tolerate much more power. A typical automotive relay will draw far less than one amp to activate the power contacts, which can handle up to 30 amperes.
The starter solenoid is a relay that can carry hundreds of amps. You don’t want that much power flowing through your key switch.
Is It Possible to Wire a Horn without Using a 3-Pin Relay?
Wiring a horn without a relay is pointless and abortive because the purpose of wiring the horn will be lost. When connecting a horn, you will need a relay, which is an important component in the horn circuit.
The relay aids in the regulation of the horn circuit’s power. It aids in the release of the linkage that completes the horn circuit, allowing it to complete the circuit and ring when engaged.
Is It Necessary to Fuse Any Relay?
You certainly should. When wiring a horn relay circuit, use the fuse/relay/load configuration. When connecting the circuit, a fuse is usually the first item to be connected. When connecting or wiring, fuse the power cable based on its size and use a fuse to protect the relay’s wire.
The relay and the fuse serve distinct functions. A relay is an electromechanical switch, whereas a fuse is a low-resistance piece of wire. When a greater current flows through the horn components, which would have burned the entire components, the filament heats up and burns/melts, safeguarding the other elements from burning.
Take a look at some of our related articles below.
- How to test a 5-pin relay with a multimeter
- How to wire a horn relay
- How to wire air horns without relay
Video References
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