Let's start by locating our relay. The relay is a small black box with four terminals that protrude from the bottom of the box.
WIRING THE 2MC/127H/228H AIR SOURCE UNITS
Each terminal on the bottom of the relay corresponds to a number. You can refer 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 pinout.
This relay needs to be placed close enough to the air source kit so that the red wire from the air source can reach over to pin # 87.
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 compressor will not turn on. Let's start with the main power connection. Locate your fuse holder that came with your kit. A picture is shown below of this component.
Our fuse-holder is sent to you in a loop. *Do not install a fuse into the holder yet.
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:
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. (Your connector may be light green instead of yellow)
The ring terminal connector can be used to connect the fuse holder to your positive battery terminal. The yellow connector will allow us to connect the fuse holder to our red wire, and complete the connection on 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.
Use the supplied 10ga terminal connector to connect the red wire to Pin 30 on the relay.
Trigger Wire (Key-Power On)
Now you will set up the key power on for the kit. This is what prevents the system from running when the vehicle is off. If not done correctly, the air source can potentially run when the vehicle is off and could drain your battery.
Start by locating the supplied roll of blue or black wire (doesn't matter which you use). Using the supplied red female quick disconnect, attach a lead of blue/black wire to Pin 86 on the relay.
From there, you will need to locate a good power source for this wire. This will differ from vehicle to vehicle. You will want to locate an accessory power wire that is only powered when the vehicle is on. If you need help locating a good source we recommend checking google for wiring schematics for your vehicle.
Below is a list of common sources that typically only come on when the key comes on. Tapping into the power wire on any of these sources using the provided red T-tap in the wiring kit, will give you the positive key power on you need for the system to only run when the vehicle is on.
- Amplifier (if applicable)
- USB Power Outlet
- Cigarette Lighter
- Daytime Running Lights
- Trailer Lights
- Heated Seat(s)
- Power Windows
Pin 85 on the relay must be run to a ground point. You can use another one of the red female quick disconnects to connect a length of blue/black wire to pin 85. Route this over to the frame of the vehicle, and use one the supplied ring terminal connectors to secure it to the frame. Be sure to use a wire brush or sandpaper to remove any oxidation/paint from the ground point. The screw/bolt you use must make contact with bare metal.
Connecting the Relay to the Air Source
At this point, you can take the red wire that comes off of your air source, and connect it to pin 87 on your relay. Once complete, your relay has been installed and is now ready for use.
Go ahead and insert a 35A fuse into the fuse holder, and turn the vehicle on. Listen for the compressor as it should begin to fill the tank once the vehicle starts up.
If it does not, double-check that your blue wire is secure to the key-power source, and check that your fuse is still intact as well.