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4x Forum - Editorial

Onboard Diagram
Christian Lee | Writer
Posted October 1, 2007

Send questions, comments, and suggestions to: 4 Wheel Drive & Sport Utility Magazine, Attn: Christian Lee, 2400 E. Katella Ave., Ste. 700, Anaheim, CA 92806, or

Onboard Air Plumbing
Q: I've seen and read about various ways to plumb an onboard air system. Basically, you have a pump and various valves and safety switches that fill a tank. However, if you want to direct the air for more than just filling up tires or running air tools, how do you "switch" the air to other sources? For example, let's say you have shocks that you can change the damping on, air lift bags for towing, ARB Air Lockers, and air for the tank. It seems silly to install multiple dedicated air pumps for each item, but what type of "air switch" exists to direct the air to an accessory?
Bob Moritz
via e-mail

A: Bob, depending on the size of the air compressor and air tank, you can run all of the accessories you mentioned and more from a single unit. A smaller compressor and air tank will do the trick for most air-driven accessories; however, it will be significantly slower in completing jobs that require constant flow for an extended period of time, such as airing four tires from 10 psi to 35 psi. According to Kilby Enterprises, a manufacturer of engine-driven onboard air systems, your accessories should be built around the compressor, not the other way around. This means that you should first establish a well-functioning onboard air system and then add the extras. Part of the "various valves and safety switches" involved in the plumbing of an onboard air system are air manifolds, which are available with varying amounts of ports to meet the needs of any air system. Typically, a manifold will host the air inlet from the compressor and the outlet to a tank, a pressure safety switch, a pressure gauge, a check valve, and an adjustable relief valve. Air manifolds can also be purchased with multiple outlets to accommodate accessories (if you plan to install more air-driven accessories, you can install a manifold with multiple outlets and unused outlets can be plugged until needed).

Most accessories, such as air lockers and air horns can be connected to the air manifold or directly to an outlet on the air tank. Air suspension or adjustable-ride shocks should typically pull air straight from the air tank. If an air tank has only one outlet, a T-connector can be used to create additional ports. Each accessory will require separate on/off switches for individual operation, and the compressor must also be switched on so it will continue filling the tank as its content is exhausted. Provided the other accessories are not switched on at the same time, only the desired accessory will function, though the others will still be ready to receive air at the flick of a switch.

For more information about onboard air system plumbing, contact Kilby Enterprises [(818) 565-5945,]. Power Tank [(800) 574-3701,] can also offer a variety of onboard air plumbing ideas.

Morse Code Not Required
Comment: First, the individuals who assemble 4 Wheel Drive & Sport Utility do a great job. I enjoy every issue. Second, it is good to see articles such as "Remote Contact" (June '07). I'm a ham radio operator and have at least one ham radio in each vehicle. There has been a change in policy regarding licensing that you may not be aware of. Morse code is no longer required for any license level. This change went into effect in February 2007 (I realize you have a publishing schedule that forces you to assemble the magazine well in advance of the actual issue date). Ham radio is a great way to communicate across the trail or across the globe. I appreciated your article.
James Reeves

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