About 75% of the total project is mounting the hardware. The rest is routing the air lines and wiring it all up. My first task was connecting the line from the compressor to the tank. While it is not absolutely critical to have the compressor close to the tank, it sure does make it easy to connect the braided steel air line. Once I had air going into the tank, I threaded a compression fitting for the 5/16" air line into the air tank and quickly discovered I would need to get some 90-degree connectors. The nylon air hose just doesn't have a very tight bending radius. I needed 90-degree connectors for both the air line to the horns, and the air intake line for the compressor. Without the angled connectors, the air line tended to get in the way of the drive shaft.
Routing the line along the inside of the frame rail is relatively easy. Routing it from the frame to the engine bay, not as much. For reasons explained later, I needed the air line to be accessible under the hood. I routed the line along the inside of the drivers side wheel well, which requires much care in securing the line. In routing the air line through this area, it's remarkably easy to let the line rest against hot engine parts on its way into the engine compartment. During my initial weekend at the farm mounting the horns, tank and compressor, I could smell something getting hot when I popped the hood after driving home. Fortunately I figured out what happened before testing the system, and even more fortunate was my earlier purchase of an extra 20 feet of 5/16" nylon air line from McMaster-Carr.
One thing I did differently than most was mount the pressure switch inside the engine compartment. While the switch appears to be relatively water resistant, I didn't want it attached directly to the tank where it could potentially take a beating on the underside of the vehicle. Plus, it would be one more small-gauge wire to take care in protecting on its way from the engine bay to the tank. To accomplish this, I needed to tee into the air line under the hood. The pressure switch would be connected at the tee and monitor pressure from that point, rather than directly at the tank. The pressure switch has a 1/8" male connection, so I found a tee at McMaster-Carr with a 1/8" male connector and two 5/16" compression fittings. A dual-female 1/8" connector from Home Depot completed the hookup.
With the air lines complete, I screwed in a drain cock and a 175 psi pressure release into the spare ports on the air tank. The remaining ports will serve as auxiliary air for whatever I can think of that might be interesting.
Giving the system some electrical juice was the next task. The compressor needs a direct line from the battery, by way of the pressure switch (with its internal relay). The Hornblasters.com instructions outline this pretty well. In between the battery and the pressure switch is a 40 amp fuse. With the compressor being the third component in my Blazer needing direct juice from the battery (the main amp and subwoofer amp for the sound system were the other two), I decided it was time for a fused distribution block from Lightning Audio.
The pressure switch needs its owns power source to function, and this power comes from the ignition wire of your choice. I chose the power wire for the cruise control module. I also used this to power the solenoid in the air valve. If wired this way (per the Hornblasters.com instructions), the pressure switch will only be functional when the ignition is on, which prevents accidental battery drain. I went a step further and added a manual switch inside the cab, just in case I didn't want the compressor running under any circumstances. The switch is wired between the cruis control module wire and the pressure switch lead. If the compressor switch relay can't get any juice, it can't turn on the compressor.
I installed a push button for activation of the solenoid, mounted in the console just under the headlight switch. The button went where some optional switch of some sort would have been (fog lights, maybe?). The wiring harness actually plugs into a plastic housing on the back side of the console, even though there's nothing there on the front side. I simply drilled out a hole big enough for the button, screwed in the button, routed the wires through the dash and firewall and put the console all back together again.
Again, I took this a step further. I tend to favor my left hand when steering, so pushing a button with my left hand would require a quick switch of hands on the steering wheel. The ideal location of a button switch would be on the shifter, but I couldn't think of a good way to mount it without calling attention to it. So I added a second button switch that's more of a hand trigger, complete with a coiled cord. While driving through the streets of Chicago, I can hold the trigger switch in my right hand and steer with my left. The second switch also lets passengers take part in the fun of blasting unsuspecting drivers and pedestrians.
