Automatic Level Control (Alc)

The Automatic Level Control (ALC) keeps the rear of the vehicle at a constant height. If weight is added to the vehicle, the ALC Sensor turns on the ALC Compressor. Air is pumped into the shock absorbers until the ALC Sensor senses that the vehicle is level.

An Actuator Arm is linked between the upper RH Control Arm and the ALC Sensor, which is mounted to the rear crossmember. It turns as the vehicle height changes. The ALC Sensor detects this motion and operates switches to control the air flow into and out of the shock absorbers.

Voltage is applied at all times to the ALC Compressor and ALC Sensor. This allows the ALC System to vent after a load is removed, even with the Ignition Switch in "OFF." Voltage is also applied to the ALC Sensor with the Ignition Switch in "RUN," "BULB TEST" or "START." Approximately 35 to 50 seconds after the Ignition Switch is turned to "RUN," the Compressor Motor will run for approximately 3 to 5 seconds. This ensures that the shock absorbers are filled with adequate residual pressure.

The ALC Sensor must detect a "Car-Low" or "Car-High" state for 7 to 14 seconds before activating the intake or exhaust outputs. This prevents system operation during normal ride motions. In addition, the ALC Sensor limits Compressor Motor run time or Exhaust Solenoid energized time to a maximum of 4.5 to 7 minutes.

This time limit is necessary to prevent continuous Compressor Motor operation in case of a severe system leak or continuous vent. Turning the Ignition Switch to "OFF" and back to "RUN" resets the 4.5 to 7 minute maximum run timer.