Automatic Level Control System Components Description

Rear Suspension Leveling Air Compressor
The compressor is a positive displacement rocking piston air pump powered by a 12-volt direct current permanent magnet motor. The compressor head castings contains the piston intake valves and contains the piston exhaust valves. The head castings also contains a solenoid-operated exhaust valve that releases air when energized. The compressor is mounted to the right rear of the body by a bracket. ALC Sensor The ALC sensor is an electronic device. The following is controlled by the

ALC SENSOR:
- The Automatic Level Control Air Compressor.
- The Exhaust Solenoid Valve. The sensor circuitry provides a 25 second delay before either circuit can be completed to prevent falsely actuating the compressor or to prevent falsely actuating the solenoid valve circuits during normal ride motions. The sensor also limits the compressor run time or the solenoid valve energized time to a maximum of 2.5 minutes. This time limit function is necessary to prevent continuous compressor operation in the case of a severe system leak or in the case of a continuous exhaust valve operation. Turnings the ignition off and on resets the electronic timer to renew the 2.5 minute maximum run time. The sensor mounts on the rear shock and spare tire crossmember. The actuator arm of the sensor attaches to the rear differential case by a link.

Rear Leveling Shock Absorbers
The shock absorber is essentially a conventional shock absorber enclosed in an air chamber. The shock absorbers are constructed with a rubber-like sleeve attached to the dust tube and attached to the shock reservoir. This makes a flexible chamber which extends the shock when the air pressure in the chamber is increased. The weight of the vehicle collapses the shock absorber when the air pressure is reduced. To maintains proper operation and to maintains reliability of the shock absorber a minimum residual air pressure of 55 kPa. (8 psi) is maintainable at all times by the air dryer.

Tubing and Fittings
The snap-on connectors attach the tubing to the rear shock absorbers. The connector housings contains retainer clips. When a tubing is attached to a shock fittings, the retainer clip snaps in a groove in the shock fittings, locking the tubing in position. All tubing fittings are sealed with two O-rings.





Air Compressor Description
The automatic level control air compressor consists of several components attached to a bracket which mounts to the right rear corner of the underbid. A rubber shield covers the automatic level control air compressor in order to provide protection from road debris.

Air Compressor Motor and Head Description
The automatic level control air compressor motor is a single piston type compressor powered by a 12 volt permanent magnet motor. The automatic level control air compressor head contains intake and exhaust ports plus a solenoid operated exhaust valve that releases air from the system when energized. Air is drawn in the automatic level control air compressor through the automatic level control air filter. The automatic level control air compressor motor attaches to the automatic level control air compressor bracket using rubber grommets in order to reduce noise and vibration.

Air Dryer Description
The automatic level control air dryer attaches directly to the automatic level control air compressor head and provides the following two functions:
- The automatic level control air dryer contains a dry chemical which absorbs moisture from the compressed air before it goes to the air shocks. The moisture is later removed from the chemical when the dry air is exhausted from the air shocks and passes back through the automatic level control air dryer.
- The automatic level control air dryer contains a calving arrangement which maintainers a minimum pressure of 48-97 kPa. (7-14 psi) in the air shocks at all times in order to minimize friction between the air shock sleeve and the. body. This minimum pressure feature improves vehicle ride and shock reliability.

Exhaust Solenoid Description
The exhaust solenoid is located inside the automatic level control air compressor head and provides two functions:
- When the automatic level control sensor energizes the exhaust solenoid, the solenoid provides a path for the exhaust air to leave the system.
- The exhaust solenoid acts as a blow-off valve in order to limit maximum system pressure to approximately 1240 kPa. (180 psi).





Automatic Level Control Sensor Description
The automatic level control sensor mounts to the vehicle underbody above the rear axle, and attaches to the rear differential case by a short link and ball stud.





The function of the automatic level control sensor is the control of two basic circuits:
- The compressor relay circuit
- The exhaust solenoid circuit
The automatic level control sensor measures the position of the vehicle body. The ALC sensor energizes the automatic level control relay circuit if the automatic level control sensor arm is above the in-trim zone (vehicle body too low). The ALC sensor energizes the exhaust solenoid circuit if the automatic level control sensor arm is below the in-trim zone (vehicle body too high). In order to prevent falsely energizing either of these circuits during normal ride motions, the sensor circuit requires a consistent automatic level control sensor arm position (vehicle consistently too low or too high) for a minimum of 7-14 seconds prior to completing the ground to either circuit.
Additionally, the automatic level control sensor circuit electronically limits automatic level control air compressor run time and exhaust solenoid energized time to approximately 51/2 minutes. This time limit is necessary in order to prevent continuous automatic level control air compressor operation in the case of a severe system leak, and in order to prevent continuous exhaust solenoid operation when the vehicle is very lightly loaded. The electronic timer is reset whenever the vehicle ignition switches from OFF to RUN or from RUN to OFF, or when certain predetermined combinations of automatic level control sensor arm position and vehicle ignition position exist.

Air Links and Connectors Description
Flexible nylon air lines, 3.2 mm (1/8 inch) in diameter, are used in order to transfer air under pressure from the automatic level control air compressor to the shocks or inflator fill valve. The system contains two air line jumpers which go to and from the inflator solenoid, and a crossover air line, which goes to the air shocks. Use snap on connectors in order to attach the air lines to system components and to provide a proper seal The air lines are flexible for easy handlings and routings. Do not kink the air lines. Keep the air lines from comings in contact with the exhaust system.

Inflator Switch Description
The automatic level control inflator air switch is located on the inflator control panel, behind the right rear body-side quarter trim panel. The automatic level control inflator air switch energizes and de-energizes the automatic level control timer relay.

Inflation Timer Relay Description
The automatic level control timer relay mounts to the back side of the inflator control panel. The function of the automatic level control timer relay is to complete the 12-volt circuits to the automatic level control air compressor and automatic level control solenoid valve. The automatic level control timer relay also prevents overheating of the automatic level control air compressor.