Help Center · Wiring

Wiring The 2MC/127H/228H Air Source Units

Wire the HornBlasters Universal Wiring Kit (WK-U) to your 2MC, 127H, or 228H air source unit — fuse holder, main power, relay ground, and relay trigger.

HornBlasters Universal Wiring Kit (WK-U)
Wire crimp tool
Wire cutter/stripper
Brain

HornBlasters universal wiring kit components

The Fuse Holder

Cut the loop and add connectors

The fuse holder included with our wiring kit comes in a loop. This can be confusing at first. Using a cutter, cut the loop in the middle to make two separate ends for the fuse holder.

Strip each end and crimp the supplied 8-gauge ring terminal to one side. On the opposite end, crimp the 8-gauge to 10-gauge connector, as shown below.

The end with the ring terminal will attach to the battery positive terminal on your vehicle. The opposite end of the fuse holder will be connected to the red power wire out to our relay.

Fuse holder with ring terminal and 8 to 10 gauge connector — Ring terminal on one end; 8ga→10ga connector on the other.

Main Power Wire

Locate the roll of 10-gauge power wire that was included with your kit. This wire will be used to connect from the fuse holder to the 40-amp relay.

Connect red wire to the fuse holder

Start by stripping one end of this red power wire and connect it to the smaller end of the crimp connector on the end of the fuse holder. Crimp the wire into the connector to complete this connection. Make sure it is tight and does not come loose.

10-gauge red power wire crimped to fuse holder

Route to the relay and crimp pin 87

Route the red wire through the vehicle back to the air compressor/tank. Find a good location to mount the relay. Make sure the relay is close enough to connect to the red wire coming off the compressor/tank. Do not connect this wire yet.

Strip the opposite end of the red wire and crimp the tan-coloured terminal connector onto the wire as shown below.

Connect this terminal connector to pin 87 on the relay. This is the pin that runs sideways, instead of vertical like the other 3. See the following image:

Your main power is hooked up and ready for use. Let's finish up the other pins on the relay.

Tan terminal connector on pin 87 of the relay — Pin 87 runs sideways — battery power feeds this pin.

Confirm pin 87 orientation

Pin 87 is the pin that runs sideways, instead of vertical like the other three pins on the relay.

Relay bottom showing pin 87 sideways orientation

Relay Ground

The ground (−) for the relay is extremely important. If the relay doesn't have a proper ground, it won't work and the compressor will never kick on and fill the tank.

Wire pin 85 to chassis ground

To start, locate the roll of grey or blue 18-gauge wire that was supplied with your kit.

Strip one end of this wire and crimp one of the small red female terminal connectors onto the wire.

Connect this lead to pin 85 on the relay, as shown below.

Route the grey wire to the frame of the vehicle (or back up to the negative battery terminal). Use the supplied 18-gauge ring terminal connector to secure the wire to the frame as a ground (or negative battery terminal). Do not use the tool box or bed as a ground, these will not work. The frame MUST be used!

Red female terminal on relay pin 85 ground — Pin 85 — relay coil ground.

Secure the ground ring terminal

Use the supplied 18-gauge ring terminal connector to secure the wire to bare metal on the frame (or the negative battery terminal).

18-gauge ring terminal for chassis ground

Relay Trigger

This is what tells the relay to turn on.

Wire pin 86 trigger lead

This connection will use the 18-gauge grey or blue wire similar to the last step. We will crimp a terminal connector onto one end of the wire as we did previously, and connect this terminal to pin 86. Your relay will look like this:

Relay with pin 86 trigger wire connected — Pin 86 — relay trigger.

Completed relay wiring on air source unit

You have reached the last article in this category. You can go back to the Help Center and browse other categories or review the previous ones.

Help Center