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 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.