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, you 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.
The ring terminal can be used to connect the fuse holder to your positive battery terminal. The yellow butt connector will allow us to connect the fuse holder to our red wire, and complete the connection back to the pressure switch. 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 pressure switch. Do not cut your red wire until you have finished routing it back to the pressure switch. You want to make sure you don't cut it too short.
Once the red wire has been routed back to the pressure switch, 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.
This connector will allow you to connect the 10ga red wire to the relay. Slide the connector over pin 87, and crimp the exposed red wire in the connector.
Pin 30 is the easiest connection to complete with this setup. Take the red lead from the compressor and connect it directly to pin 87 on your relay. This should be the last connection needed for the relay.
Finishing up the Pressure Switch
Now that our relay is wired up, you are now left with one side of the pressure switch to complete.
You will connect this side of the pressure switch to a key-power-on source on the vehicle so that the compressor can only run when the vehicle is on. If you connect this wire to the battery, the compressor could run overnight and drain your battery.
Start by locating the supplied roll of blue or grey wire (doesn't matter which you use). Using the supplied red female quick disconnect, attach a lead of blue/grey wire to the prong on the pressure switch.
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.