Onboard Air Installation (12 volt)

By jprtroy

I started shopping for an air compressor that would meet my needs, fast, and continuous duty, I found it at Extreme Outback Products. I ordered their Extreme Air severe duty compressor.

I also ordered most of the accessory components for it (pressure switch, check valve, 100A circuit breaker, pop-off valve, and solenoid). I purchased my air from a local truck wrecking yard, for $25, (4 to 5 gal capacity).

I had to fab up and weld brackets to my tank in order to mount it under my bed in front of the driver side rear wheel so, out came my welder and steel. A few hours later, I had new mounting rails welded to my tank. I mounted the tank to the underside of the bed, to the cross members so there are no bolts exposed in the bed.

I made sure to leave enough space at the trucks cab for whatever fittings I may need to install in the tank. The tank has 4 ports, two 3/4" NPT ports on either end, and two 1/4" NPT ports, one up high on the side (used for my pop-off valve) and one directly below a 3/4" port at the outer edge of the tank. I put a drain cock in this fitting.

The two 3/4" ports are used for supply and delivery. Supply & delivery through a manifold

Now was the time I needed to determine what would eventually be connected to my air system and to plan for those additions. I knew I'd have an air horn of some sort's, so I have a port ready for that. I figured eventually I'd require a Quick-disconnect, (QD for short) for the front of my truck, so I have a port set-aside for that as well. I also knew I'd have an air gauge mounted in the cab, so I allowed a port for that also. All these ports are made up from 1/4" brass T's ganged together with 1" unions. All unused ports are plugged with 1/4" plugs.

For the supply & delivery sides I needed a few fittings that weren't in my pile of fittings so off to OSH I went. I picked up all the necessary T's, plugs, reducers, elbows unions, etc. and assembled everything on the tank end. Unfortunately, when I placed the tank into position with the supply fittings in place, the fittings were extremely close to the bottom of the cab (like less that 1/8") nothing a ball peen didn't fix though! (Had to hammer back some body flashing that's all)

Once the clearance issues were dealt with I lowered the tank and installed the pop-off valve, the drain cock, and my output QD. I also decided to install a Schrader tire valve so I can add air from an outside source.

Tank is now done and installed. Time to work on the compressor.

The compressor is somewhat huge; locating it under the hood is not an option. I choose to locate it under the bed opposite of the tank

This time, though I had to drill through the bed, as the support ribs weren't positioned properly this time. I made a paper template of the mounting holes on the compressor by setting a sheet of paper (taken from my printer) on the compressor and rubbing my dirty fingers on the holes. Thus leaving dirty little circles on the paper. Held this sheet to the body of the bed and marked it for drilling.

Drilled the bed, then, realized I didn't have any matching bolts long enough to actually bolt the thing up. Off to Ace I went. Reason I needed long bolts is, I used some 1/2" thick rubber as isolation between the truck bed and the compressor. With proper hardware in hand, I bolted the compressor in place. Looks good up under there! Now that that's done, I get to plumb the compressor to the tank.

Plumbing lines. Would have been much easier had I chosen to use copper line, but NO, I wanted stainless steel! Heck, I have about 100' of the stuff, so I went with it. Quickly realized I had no way of bending the SS tubing. (used to work for a place that had that stuff!) Off to OSH I went.

With a proper tubing bender now in hand I set out to plumb the compressor. A few hours, and many curse words, and bloody knuckles later, I done it! The SS line is kind of hard to see.

Now it's time to deliver power to the compressor. This step took a few weeks to actually start and finish. Mainly, where was I going to mount the circuit breaker? Anyone familiar with CTD's know there's not a lot of free space under the hood. I still have the stock air box, which takes up a lot of real estate. I finally settled on a place located on the firewall, above the PCM. I cut the padding drilled 2 holes and fixed the CB in place.

The solenoid came next. This wasn't so hard to install. I choose a flat spot under the bed close to the compressor, and drilled 2 holes and used 2 10/32' bolts to mount it up.

I ran 8ga wire from the battery (protected in wire loom) to one post on the circuit breaker. 8ga wire from the circuit breakers other post, back to one post on the 100A solenoid. Reason for the large wire size, it the compressor is rated to draw 60A at full load. It has a ' hp motor (winch motor) The other solenoid post has the compressor hot lead connected to it. The GND lead of the compressor is grounded to a good ground source.

All that's left now, is locating the switch to turn the thing on and wire it up. This took its toll on my gray matter! I really couldn't find a suitable spot that would be easy to locate a 30A toggle switch. Not without some dremal work anyhow. I removed the knee panel, and determined that the switch I had purchased for this would work, but I couldn't use the female spade connectors to affix the wires to it. I had to solder them on. Not enough room behind the switch when mounted in place. So I soldered 3 wires (red, yellow and black) to the switch. Red for 12vdc, yellow for the solenoid ON, and black for GND.

Okay, now I need to get 12vdc to the switch, then back out to the solenoid's relay control. (to actuate the thing). The Solenoid wire (yellow 14ga) was ran along the same path as the 8ga power wire, up into the engine compartment along the main wire harness for the motor, then down into the rubber feed (driver side) through in the firewall, to the yellow wire with a female spade connector. 12vdc is supplied to the switch (on a red 14ga wire) through an aftermarket ATO style fuse block with a 3A fuse installed (8 fuses total) the fuse block gets juice via a 10ga red wire through a 30a circuit breaker.

I used a terminal block to distribute voltage as I plan on a few more accessories requiring 12vdc. Some will be for 'key on' others not. The TB allows me, to have one line in and many lines out.

After double-checking all electrical connection, I made the final connection to the battery, (no sparks, good thing!) I went to the switch to fire it up, and CLANK, heard the solenoid close, but the compressor didn't come on? Doh' forgot to reset the big circuit breaker. With that done, the compressor came to life. I haven't timed how long it takes to fill the tank yet. With the motor running, I can just hear the compressor. With the stereo on, the compressor can't be heard!