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HomeTips & GuidesHow To Make Your Own Wire Harness For A Car Horn

How To Make Your Own Wire Harness For A Car Horn

How To Make Your Own Wire Harness For A Car Horn? From a technical point of view, your vehicle will move from point A to point B without a functioning horn. 

However, driving around without a functional horn risks your safety and that of other drivers and pedestrians.

Not to mention that in most places, driving without a functional horn is illegal. 

Therefore, learning how to make your own wire harness for a car horn could be useful if you encounter any issues with your horn.

Table of Contents

How Your Horn Works:

A car horn is a simple electrical circuit similar to a doorbell. 

When you press the button, the circuit closes, allowing electrical current from the battery to flow to the horn. 

Hence, the horn produces a warning sound.

Horn Wiring Illustrations

Wiring a horn is rather simple because your car already has one installed. 

Some cars use simple wiring without the relay, but most have one.

 Simply unplug the horn to listen for a click when you press the button to determine if there’s a relay.

There are two horn types: air horns and electro-mechanical horns.

 Air horns have a tiny air compressor, and electro-mechanical horns are the standard horn. Both electro-mechanical and air horns generally have the same wiring.

 However, an air horn normally needs increased current (almost twice the amount of electro-mechanical horns). 

Hence, ensure your fuse and wiring can handle the draw of current from your horn. 

Therefore, locate the horn fuse and confirm the amp rating. Often, it will be 10 amps or higher. Generally, the bigger the horn, the more power it draws.

The wire capacity for your horn can lean a little bit toward the slimmer side because you use the horn intermittently. 

If not, it’s best to opt for the recommended wire gauge for air horns drawing high amounts of power.

Keep in mind your car uses two horns to give a comfortable tone. One is high tone, while the second is low tone.

The Wiring of Horn Switch Grounding Relay

For this scenario, the horn switch closes the horn circuit to complete the ground. 

Normally, a wire connects to the horn button and the switch grounds the wire to close the circuit.

 The wire and size of the fuse you should use depends on the current rating of the horn. 

The gauge of wire you should use depends on the power drawn to your horn.

Horn Switch 12V Relay Wiring

Although the previous wiring example is common, it isn’t always the case. In some vehicles, you might find two wires connected to the switch.

The key difference is that you’re switching the 12V side to determine whether you had a horn switch. 

Therefore, you would have to feed it 12 volts and then pass that back to the relay. 

If your current steering wheel only has one wire connecting to the horn button, you can ignore this and refer to the first example.

Reasons Your Horn isn’t Working

You can trace any issues in the horn system back to any of the elements in the path of the electrical circuit sending current to your horn.

Fuse Issues

Often, a blown fuse is the cause of most horn issues. Similar to most car electrical systems, the horn circuit uses a fuse.

 The fuse blows if the circuit shorts out, overloads, or experiences any other issues. 

The fuse is a shield to prevent extreme damage to the horn system.

To fix this issue, you’ll need to follow the steps below.

  • First, check the car’s manual to determine the location of the horn fuse within the fuse box.
  • Next, remove the horn fuse and inspect it for any signs of damage. Also, confirm that the fuse has the correct rating according to the manual.
  • Then, if the fuse is blown, you’ll have to replace it with a new one. Ensure the replacement fuse is of the correct rating.
  • Lastly, put everything back in place and confirm if your horn is functional.

Relay Issues

Similar to the fuse, the relay is also located in the fuse box. The relay controls the amount of power delivered to the horn.

 A bad relay could prevent the horn from functioning. If you have a bad relay, you might hear a clicking sound from the relay upon trying to use the horn.

To fix the issue, follow the steps below.

  • Remove it from the fuse box.
  • Then, proceed to install a replacement horn relay.
  • Finish by turning on your car and testing if the horn works.

Horn Unit Issues

Since the horn is found at the front of the car, you constantly expose it to the elements. 

Therefore, it can suffer damage from snow, road salt, ice, or impact from roadside debris. 

Most vehicles use one horn, while some use up to two or three horns. 

So you might hear a clicking sound, low power sound, or no sound when you attempt to press on the horn. 

At this point, it’s safe to assume you already looked at the relay and fuse. 

If the horn still isn’t working, you can try pressing the panic button on the remote key fob if your case has one. 

However, if your car doesn’t have a remote key fob, you’ll have to run it to the mechanic for further diagnostics. 

Horn Switch Issues

The horn switch is normally found at the center pad of your car’s steering wheel. 

Pushing the switch closes your horn’s circuit, sending power to the horn to activate it. 

Unfortunately, the driver-side airbag is also found in the center pad.

 Therefore, it’s best to leave any repairs to a professional mechanic to avoid the risk of your airbag exploding.

Steering Wheel Uncovered

Caption: Steering Wheel Uncovered

Clock Spring Issues

Do you ever think about how your horn switch maintains an electrical connection despite the direction the steering wheel is turning? 

This is all thanks to the clock spring. Therefore, a faulty clock spring affects the connection between the horn and the car system, preventing the horn from functioning when you press it. 

Also, since the clock spring maintains contact with your driver-side airbag, you might notice an airbag warning light on the dash screen. 

This may affect other steering wheel controls like the radio, cruise control, and phone.

Simply replacing the clock spring should fix the problem. However, remember that since the airbag is involved, it’s best to have a mechanic fix the problem for you. 

Wiring Issues

If all the components mentioned above are in good condition, the wiring could be the final issue. 

Your horn circuit wiring could be faulty due to a broken wire, loose connection, bad ground connection, short because of worn insulation, or corrosion. 

It’s best to have your mechanic take a look to find out the exact problem and fix it to have your horn up and running.

How to Make Your Wire Harness for a Car Horn?

It’s best to use a pigtail wiring harness/socket wiring harness to appear as factory installations if the wiring is neatly done.

Protecting the Circuit

If you configure the relay harness correctly, it will have fuses in the power supply side of the power circuit. They will be as close as possible to the alternate or battery terminals.

If you add any additional wires that weren’t in the car’s original design, ensure you protect the new circuits. You can either use a fuse or manually reset circuit breakers

The relay harness connects to the car’s primary electrical feed (alternator or battery).

 The battery pumps between 80 and 100 amps, while the alternator pumps 60 or higher.  

A fire will spark if the new wiring shorts to the ground without protection. Plus, the wires heat up immediately due to the 130A flowing through. 

Choosing Wire

Avoid using solid copper wires; instead, use stranded copper wires for automotive applications. 

An ordinary wire insulation option could be PVC. TXL or GXL is resistant to almost everything, like repeated flexing, oil, heat etc. 

Wire gauge choosing is very important to the success of circuit upgrading. 

A wire that’s too small will result in a voltage drop, while a wire that’s too thick won’t make a durable and steady connection at the terminals, thus causing mechanical hardships because of its stiffness. 

A 14 AWG wire is normally the right size, while a 12 AWG wire is often too big. However, a 10 AWG wire steers more into the overkill territory. 

Never fail to use the right gauge wire to ground and feed the legs of the circuit because inadequate grounding causes a voltage drop

Also, running big wires to the feed side and leaving the smaller ground wires in place only sabotages your setup. 

Furthermore, a number of factory circuits run unspecified ground wires to the car body near the horn. 

This is not such a good ground, especially for a new vehicle, since as the car ages, dirt and corrosion build-up, increasing resistance between the body and ground side. 

You should run the new huge wires to the battery negative cable or alternator’s metal housing. 

Working with Wire Termination

Wires typically have two terminals: a spade connecting the wire to the alternator and a ring connecting the wire to the battery. 

Use the correct size of terminals and a high-quality crimp tool. 

You can solder your connections if you’re good with a soldering iron. 

However, soldering combines a durable and good harness; opting for other techniques is best.

Conclusion

If you’re going through the trouble of fixing factory wires, it’s best to do a complete job and run proper wires up to the car horn.

 However, getting the appropriate parts and pieces to facilitate such an improvement locally could be difficult. 

Lucky for you, Cloom has all the necessary components that your car originally came with to facilitate the improvement.

I am Lillian Yang, having been a sales manager for over 10 years.

I have received many positive reviews from customers. They have praised our excellent service, on-time delivery, and high-quality cable assemblies.

For your projects, please provide cable assembly files/images/smples, etc., so that I can send you a quotation within 24 hours.

Contact me now and let’s get started on building your wire harnesses!

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