GM Service Manual Online
For 1990-2009 cars only

Object Number: 228025  Size: SH

The Automatic Level Control (ALC) system automatically adjusts the rear height of the vehicle in response to changes in vehicle loading.

The ALC system consists of a height sensor, an air compressor assembly (5), an ALC compressor relay, an intake hose and filter, an air tube (2), and two rear shock absorbers (3). The air compressor assembly consists of an air compressor and an air dryer (1) mounted on a bracket. The air compressor head is a replaceable part of the air compressor. The exhaust solenoid is a non-replaceable part of the air compressor head.

The compressor is activated when the ignition is on, and weight is added to the vehicle. The exhaust solenoid is connected directly to the battery (+), enabling the system to exhaust with the ignition off when excess weight is removed.