Suspension Control ( Automatic - Electronic ): Description and Operation

ELECTRONIC LEVEL CONTROL (G67)


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

An Actuator Arm is connected between the rear axle control and the ELC Height Sensor, which is mounted on the body. 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 and ELC Compressor Assembly Exhaust Solenoid. This allows the ELC system to lower or raise the vehicle height even with the Ignition Switch OFF. Voltage is applied to terminal 5 of the ELC Height Sensor only with the Ignition Switch in RUN. The Compressor, after an initial delay, will run for a few seconds to charge the system when the Ignition Switch is turned to RUN.

The ELC Height Sensor delays 13-27 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 Exhaust Solenoid energized time to a maximum of 2 1/2 minutes.

This time limit is necessary to prevent continuous Compressor operation in case of a severe system leak or continuous Exhaust Solenoid operation. Turning the Ignition Switch OFF and ON resets the 2 1/2 minutes.

RAISING THE CAR
When a load is added to the vehicle, the car body is moved downward and the Actuator Arm rotates upward. Switch B closes in the ELC Height Sensor. After a 13-27 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.

LOWERING THE CAR
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 a 13-27 second delay, switch C closes. The Exhaust 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), and switch A opens. The Exhaust Solenoid is no longer energized.