Compressors are the heart of the system, but they can’t run continuously. A compressor is rated by the pressure it will produce, but even more important is the duty cycle, which is how long it can run in a given period of time. Most compressors have a 50-percent duty cycle, which means that the compressor can run for 10 minutes, then must be off for 10-minutes. During the “on” time the motor is pressurizing the tank, during the “off” time, the suspension uses the air stored under pressure in the tank. If the suspension is raised and lowered too frequently the compressor’s motor will run longer than it should, which leads to overheating, which will shorten its life considerably.

Choosing A Storage Tank

In most cases a storage tank will be part of an air suspension system and Joe cautions that this is one case where bigger is not necessarily better. The air capacity of the tank has to be matched to the volume produced by the compressor. Joe recommends one DC5000, or DC7500 compressor for each 3-gallons of tank capacity. He adds that larger air tanks are OK, as long as the system has the capability to fill them. Joe also points out that it takes longer for one compressor to fill a big tank and the lifespan of the compressor will be drastically shortened if it is overworked.

Its recommended that all tanks be equipped with a drain valve and the system must have a pressure switch to turn the compressor on and off. Joe cautions that when more than 135 psi is required to shut off the pressure switch the bags are too small in diameter.

Control Systems

In our experience, it’s always best to control bags individually. In some cases the bags on one axle are hooked together, however, this can cause them to transfer air when cornering. As the truck leans, air is transferred from the bag under a heavier load to the other side, which makes the truck lean even more.

The simplest and most affordable air control system is a Schrader valve (just like those used to inflate and maintain the pressure in tires). These manual valves can be installed in a hidden location. Schrader valves are also handy to have to inflate a bag in an emergency if there is a problem with an airline.

Pneumatic Valves

These are miniature valves that connect directly to each airbag to control their inflation. For a two-bag system there will be two up buttons and two down buttons and usually one gauge with two needles. Four bag systems will have four sets of buttons and two dual-needle gauges. These controls typically use ¼-inch airlines.

Electric Valves

These systems use switches to control electrically operated valves to inflate or deflate the bags and are much faster than the pneumatic style.

With electric controls, each bag will have a switch with three positions—up, down and neutral. Again, dual needle gauges are often used, however, controls with digital readouts are also available.

Water Traps/Air Dryers

The biggest enemy of air systems, particularly electric control valves, is contamination from moisture. When air is compressed, condensation forms in the system and that can cause steel air tanks to rust. That rust finds its way into the valves and prevents them from operating properly. The best protection from this is upgrading to a stainless steel tank.

In addition, air systems should be equipped with a water trap. The simplest is a manual drain on the tank. The problem is you have to remember to use it regularly. A better choice is an automatic drain. When installing a water trap it should be placed on the outlet of the tank before the valves.

Another source of contamination is often the installer. The careless use of sealant and Teflon tape can result in trash in the system that will get caught in the valves. Use sealant sparingly, and start Teflon tape one or two threads from the end of the fittings.