Circuit Operation

ELECTRONIC LEVEL CONTROL
The Electronic Level Control (ELC) keeps the rear of the vehicle at a constant height. If weight is added to the vehicle, the ELC Height Sensor turns on the ELC Compressor. Air is pumped into the shock absorbers until the vehicle is level.

An Actuator Arm is connected between the rear axle tie rod and the ELC Height Sensor which is mounted to the rear crossmember. It turns as the vehicle height changes. A solid state unit 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 ELC Height Sensor, ELC Relay, ELC Compressor Assembly Vent Solenoid and ELC Inflation Timer Relay. This allows the ELC system to lower or raise the vehicle height even with the Ignition Switch in "OFF." Voltage is applied to the ELC Height Sensor with the Ignition Switch in "RUN," "BULB TEST" or "START." The Compressor, after an initial delay of approximately 40 seconds, will run for a few seconds to charge the system when the Ignition Switch is turned to "RUN."

The ELC Height Sensor delays 8-15 seconds after a change in vehicle height before closing switch C in the ELC Height Sensor. This prevents system operation during normal ride motions. In addition, the ELC Height Sensor limits Compressor run time or Vent Solenoid energized time to a maximum of 5 1/2 minutes.

This time limit is necessary to prevent continuous compressor operation in case of a severe system leak or continuous vent. Turning the Ignition Switch to "OFF" and back to "RUN" resets the 5 1/2 minute maximum run time.

LOWERING THE VEHICLE
When a load is removed from the vehicle, the vehicle body is moved upward and the Actuator arm rotates downward. Switch A closes in the ELC Height Sensor. After an 8 to 15 second delay, switch C closes. The Vent Solenoid is energized and air is exhausted from the air shocks. As the vehicle body moves downward, the Actuator Arm is rotated back to its original position (plus or minus 1 inch), switch A opens and the Vent Solenoid is no longer energized.

RAISING THE VEHICLE
When a load is added to the vehicle, the vehicle body is moved downward and the Actuator arm rotates upward. Switch B closes in the ELC Height Sensor. After an 8 to 15 second delay, switch C closes. The coil in the ELC Relay is energized and the Relay contacts close. Battery voltage is applied to the Compressor Motor. The Compressor operates and pumps air into the adjustable shock absorbers. As the air shocks inflate, the vehicle body moves upward. When the Actuator Arm rotates back to its original position (plus or minus 1 inch), switch B opens, the Relay is no longer energized and the Compressor stops.

INFLATOR
A provision is made to use the Compressor to inflate tires, etc. The inflation equipment consists of the ELC Inflation Timer Relay, Inflator Switch and Inflator Solenoid Valve Assembly. When the Inflator Switch is turned to "ON," it grounds the ELC Inflation Timer Relay, which operates the Inflator Solenoid Valve Assembly and turns on the Compressor via the ELC Relay. The Inflator Solenoid Valve Assembly redirects the compressed air from the suspension to the inflator hose.

The ELC Inflation Timer Relay limits inflation operation to 10 minutes each time the Inflator Switch is operated.