Air Spring Suspension: What When Where Why and How

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Air Spring Suspension: What When Where Why and How

Postby oldschool1 » Mon May 11, 2009 10:53 pm

Air Spring Suspension Operation

The air suspension leveling system operates by adding or removing air in the spring to maintain the level of the vehicle at a predetermined front and rear suspension height. The predetermined distance is known as the vehicle trim height. Trim height is controlled by the height sensors. Distance of the body to ground will change with the tire size and inflation pressure.

The height sensors are attached to the body and the suspension arms, and will lengthen or shorten with suspension travel. Three height sensors are used: One at the left front wheel, one at the right front wheel, and one for the rear suspension.

The system works in the following manner: As weight is added to the vehicle, the body will settle under the load. As the body lowers, the height sensors shorten (low out-of-trim), generating a signal to the control module which activates a signal to the air compressor (through a relay) and opens the air spring solenoids. As the body rises, the height sensors lengthen. When the pre-set trim height is reached, the air compressor is turned off and the solenoid valves are closed by the control module.

A similar action takes place whenever weight is removed from the vehicle. As weight is removed, the body will rise, which causes the height sensors to lengthen (high out-of-trim), generating a signal to the control module which opens the air compressor vent solenoid and opens the air spring solenoid valves. As the body lowers, the height sensors shorten and when the pre-set trim height is reached, the air compressor vent solenoid is closed and the air spring solenoid valves are closed by the control module.

Air required for leveling the vehicle is distributed from the air compressor to each air spring by four nylon air lines which start at the compressor dryer and terminate at the individual air springs. The dryer is a common pressure manifold for all four air lines so orientation of these lines at the compressor is not required. However, the air lines are color-coded to identify to which air spring they are attached. The dryer contains desiccant (silica gel) which dries the compressed air before delivering the air to springs. During venting of any air spring, the previously dried air passes through the dryer to remove moisture from the desiccant (regeneration). Air required for compression and vent air enter and exit through a common port on the air compressor head. Vented air is also controlled by a solenoid valve in the compressor head.

CAUTION: The compressor vent solenoid and all air spring solenoids have internal diodes for electrical noise suppression and are therefore polarity sensitive. Care must be taken when servicing these components not to switch the battery feed and ground circuits or component damage will result.

Source: FPS 365-126-86B


Last bumped by oldschool1 on Mon May 11, 2009 10:53 pm.
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