40 Amp Relay
Bottom of 40 Amp Relay

Let's start by locating the relay. The relay is a small black (or red) box with four terminals that protrude from the bottom of the box.

Each terminal on the bottom of the relay corresponds to a number. You can reference back to these numbers when looking at a relay wiring diagram. All of our relays are laid out in the same fashion as above. If the numbers on your relay cannot be read, you can reference the following diagram for the pin out.

40 Amp Relay Pin Layout

Wiring The Relay

This is one of the trickiest parts of the install, and rightfully so. If the relay is not wired exactly right, the horn will not make any sound.

Electric Horn Wiring Diagram

The diagram above shows how the direct-drive compressor can be connected to a push-button.

Each number on the diagram corresponds to each pin on our relay as we mentioned above. You will be using Female Quick Disconnects to complete these connections. Each connector looks like the following:
Red Terminal Connector

You will use this connector for terminals 85 and 86.

Pin 30

Pin 30 will connect to the positive terminal of our car battery. For this connection, you will be using the red (10ga) wire that came with your kit. You will also use the fuse holder here as well.

Our fuse-holder is sent to you in a loop. *Do not install a fuse into the holder yet.

Fuse Holder

Go ahead and cut the fuse holder in the center to make two ends. You can cut the wire where the dashed line is in the picture above. Using a set of wire strippers, strip each end of the holder and expose the copper leads. Each end should now look like this:

Stripped Wire

At this point, we will use the supplied ring terminal crimp connector on one side of this fuse holder. The opposite end of the fuse holder will accept one of the yellow butt connectors included with the electrical connectors. The two connectors are pictured below.

Yellow Ring Terminal

Yellow Butt Connector

The ring terminal connector can be used to connect the fuse holder to your positive battery terminal. The yellow butt connector will allow you to connect the fuse holder to the red wire, and complete the connection back to the relay. Go ahead and strip one end of the supplied red wire, and connect it into the opposite end of the yellow butt connector. Route your red wire from the fuse holder back to the relay. Do not cut your red wire until you have finished routing it back to the relay. You want to make sure you don't cut it too short.

Once the red wire has been routed back to the relay, you can cut off any excess wire while still leaving a small amount of slack. Now, locate the neon green terminal connector in your electrical kit.

Yellow Terminal

This connector will allow you to connect our 10ga red wire to the relay. Slide the connector over pin 87, but do not crimp the connector yet. You will add another small wire here later.

Pin 87

Pin 87 is the easiest connection to complete with this setup. Connect a lead of red wire from the positive terminal on the direct-drive compressor and connect it directly to pin 87 on your relay. You will use two more of the light-green connectors above.

Pin 85

Pin 85 is a ground connection for the relay. This pin will get routed over to the frame of the vehicle as a ground with the push button in between. The red terminal connector will simply slide over the pin on the relay, and you may crimp an exposed lead of 18ga wire into the connector. You will be using the push button in between the relay and the ground point, to make and break the ground connection. This in turn will allow the relay to turn on/off as you press the button. Take one lead of the button to pin 85 on the relay, and the opposite lead of the button to the desired ground point.

Pin 86

Pin 86 will connect to pin 30, using 18ga wire. You can strip the end of the grey or blue wire and connect it into the same crimp connector your red wire is connected into. Once both leads are in the connector, go ahead and crimp the wires into it. Crimp the opposite end of the blue/grey wire into the terminal connector on pin 86.

At this point, your relay is wired and can be tested. Insert one of the supplied 35A fuses into the fuse holder and press your horn button. The compressor should start to make a whirring sound, indicating that it is pushing air. If it sounds like it is grinding, check the connections at the compressor itself. This usually happens if the positive/negative connections are backward.

Up next is the wiring for our Motorcycle & Truck Electric Air Horns!