Car and Motorcycle Horns

Horns are used on all sorts of vehicles from motorcycles, cars, trucks, utility vehicles and so on. They are a very simple device and come in couple of styles. These include Diaphragm, Horn, and Air Horn styles, some even play music like La Cucaracha, or Dixie like in The Dukes of Hazzard County.

Wiring up an existing horn is pretty simple, and depending on your application you may want to use a relay to hook it all up. More on the shortly. The Introduction to Automotive Relays can also help with fresh installs.

How to Wire a Horn

I'll be skipping how a horn works, this is more how to hook them up.  One common question in doing so is How Much Current Does It Draw? Well I have collected a list of common aftermarket horns (both Electro-mechanical and Air) so you can figure out the first step. In general most new cars and trucks (even motorcycles) have relays driving the horns from the steering wheel so replacing an existing horn is pretty easy. The only thing you need to worry about in that case is current draw.

Here is the big list of horns I mentioned, it's broken down by manufacturer and by horn type -

Reference Library Quick Links Ford 302 HO and 351W Firing Order Ford 260 289 302 Firing Order Flathead Ford Firing Order Ford 351C, 351M, 400M Firing Order Big Block Ford FE 390 427 428 Firing Order Ford 429 and 460 Firing Order Chevy SB and BB Firing Order Chevy LSX Firing Order Powerstroke 6.9L and 7.3L Firing Order Mopar Firing Order Porsche Boxster and Cayman Firing Order Porsche 911 Firing Order Ford V6 Firing Order Mini Cooper Firing Order BMW Inline 6 Firing Order Datsun L16, L18 and L20 Firing Order Pontiac V8 Firing Order Reading your Spark Plugs How to Measure 5 Lug Bolt Patterns on Wheels Measuring 4, 6, 8 Wheel Bolt Patterns Wheel Lug Torque Sequence Ford 302 HO and 351W Valve Adjusting Order Ford 260, 289 and 302 Valve Adjusting Order Drill and Tap Chart Inch Drill and Tap Chart Metric Drill and Tap Chart British Sheet Metal Gauge Chart Small Block Ford Valve Layout Small Block Ford Head Torque Sequence Small Block Ford Intake Torque Sequence Big Block Ford Intake Torque Sequence Big Block Ford (FE) Head Torque Sequence Big Block Chevy Valve Layout Big Block Chevy Head Torque Sequence Big Block Chevy Intake Torque Sequence Small Block Chevy Head Torque Sequence Small Block Chevy Intake Torque Sequence Chevy LSX Intake Torque Sequence Powerstroke 7.3L Head Bolt Torque Sequence Wheel Camber Examples Wheel Offset Examples Bolt Grade Markings EZ Read Bolt Torque Chart Inch EZ Read Bolt Torque Chart Metric Socket Head Cap Screw Torque Chart - Inch Socket Head Cap Screw Torque Chart - Metric Introduction to Automotive Relays Automotive Horns Automotive Electric Fans Automotive Flashers Headlight Relay Wiring Steering Wheel Hub Patterns Electric Fuel Pump Wiring Diagram Drive Shaft Angles and Vibrations

Horn Switch Grounding Relay Wiring

In the example above the horn circuit is closed by the horn switch completing the circuit to ground. This is a very common steering wheel wiring schematic. Usually their will be one wire coming into the horn button and to close the circuit the switch grounds that wire. This is not always the case, but a very common one. You may ask what size fuse or wire should I use? Well depends on your horn(s) current ratings start with a fuse at that or just larger. For wiring size of power to your horn use this wire size calculator. (Note: The control terminals 85 or 86 which can be thin 18 gauge wire). If you are wiring up an Air horn it would look the same, the Air compressor positive wire would come from terminal 87 (just like above) and the ground wire from the compressor would tie to a bolt on the chassis.

Car Horns and You Conclusion

So we have shown a couple of common examples how to wire up your horn(s). Doesn't matter if a boat, car, motorcycle or RV. Some smaller vehicles (motorcycles as an example) may not have a horn relay. It's important to make sure the current draw is not too high for the switch, fuse or wiring if that's the case.  The relay is a good addition to the mix if you don't have one switching your horns.

Some Tips

Don't expect to use an Air Horn without a relay and appropriate wire and fuse changes
Most horns sound better when used in pairs one High Tone, one Low Tone
If your horn has only one connection, the mounting bracket will be the GROUND
Some of the Manufacturer links above (or from their main web sites) have sound samples of the horns


Happy Motoring!

Horn Wiring Examples

Wiring up horns are pretty easy since your car likely has one already. Some cars have simple wiring that does not use a relay but most have the relay. Start with a wiring diagram of your car (or Motorcycle, RV, etc.) and see how they hook it up. If you can't find a wiring diagram you can see if it has a relay by unplugging the horn and listening for a mechanical clicking when you push the horn button.

One of the most important things is making sure your wiring and fuse can handle the current draw for your horns (or Air Compressor for your Air Horns). Find the Horn fuse and check the amperage rating. It's likely to be 10 Amps or greater. Bigger horns (generally) draw more power. The largest draw seems to be for Air horns.

Their are basically 2 types of horns we will talk about, Electro-Mechanical and Air horns. Electro-Mechanical are just the standard style horn, diaphragm, etc. Air horns are ones with a small air compressor.

Both Air horns and Electro-Mechanical horns are hooked up basically the same way, however Air Horns typically require a lot more current, almost 2x of the simple electrical brothers. It's very important to ensure your wiring and fuse capacity is correct. Wiring capacity for horns can afford a bit of leaning to the smaller side since the Horn is intermittently used... If that's not the case stick with recommended wiring gauge, especially for the larger current drawing Air Horn types.

Again don't forget that typically 2 horns are used on cars to provide a pleasing tone, one horn is a LOW tone and the other is a HIGH tone. Just make sure you check the charts for the current draw.

Below are 2 images with typical wiring diagrams for hooking up you horns. Air horns can be interchanged with Electro-mechanical horn types but be aware you may need larger fuse, wire and the use of a relay. In all cases it's better to use the relay to switch the high current draw of the horns unless you are using small low powered units, for example my Sunbeam Tiger does not use a horn relay, but likely should... Ah British wiring ;)

Common Automotive Horns

Below is a chart of common Automotive horns. They should look similar to something on your car, motorcycle, or boat.
Nothing magical, some OEM horns may have a different shape but almost all are based on one of the pictures below.

Some things to note -

If you horn has only ONE terminal the mounting bracket will be your Ground connection. So the single terminal horn Positive lead will go to the connector, the the chassis ground will complete the circuit.

If your horn has 2 terminals you may ask which is Positive and which is Negative? Well if they are marked with polarity or a red (+) and a black (-) that is how you hook them up. If their are no markings you can generally hook them up either way. This applies to either Horn shaped (top row) or Diaphragm (middle row) horns.

For Air Horns you will need to connect them up in a similar way, most Air Compressors for air horns have a marked Positive (+) and Negative (-) terminal. In the case where one might exist, the mounting bracket and case are likely the ground.

Horn Switch 12 Volts Relay Wiring

The previous wiring example showed the horn switch ground the wire to complete the connection. On some cars you may find 2 wires connected to the switch. Or decided to wire up something this way for some reason maybe via a push button switch. In any case this is what the other typical wiring for you might use. My feeling is newer cars have this scheme but not really sure if I can make a blanket statement without more research.

The main difference is that you are switching the 12 Volt side, so as you can see if you had a horn switch you would have to feed it 12 Volts, then again pass that back to the relay. If your existing steering wheel has only one wire into the horn button, this is not the one you use, look to the previous example!