Suspension Control ( Automatic - Electronic ): Description and Operation

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

An Actuator Arm is linked between the upper RH Control Arm and the Height Sensor Assembly, which is mounted to the rear crossmember. It turns as the vehicle height changes. The Height Sensor Assembly 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 Compressor Assembly and Height Sensor Assembly. This allows the ELC System to vent after a load is removed, even with the Ignition Switch in "OFF." Voltage is also applied to the Height Sensor Assembly 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 Height Sensor Assembly must detect a "Car-Low" or "Car-High" state for 7-14 seconds before activating the intake or exhaust outputs. This prevents system operation during normal ride motions. In addition, the Height Sensor Assembly 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.

RAISING THE VEHICLE
When a load is added to the vehicle, the vehicle body is moved downward. When the Height Sensor Assembly has detected a "Car-Low" state for 7-14 seconds, the Intake Control Switch is closed to ground. With CKT 321 grounded, the coil in the Compressor Motor Relay is energized and the relay contacts close. Battery voltage is applied to the Compressor Motor, which operates the Compressor and pumps air into the adjustable shock absorbers. As the shocks extend, the rear of the vehicle rises. When the vehicle body reaches its original height +/-25 mm (1 inch), the Height Sensor Assembly opens the Intake Control Switch, de-energizing the Relay coil and the Compressor Motor stops.

LOWERING THE VEHICLE
When a load is removed from the vehicle, the vehicle body is moved upward. When the Height Sensor Assembly has detected a "Car-High" state for 7-14 seconds, the Exhaust Control Switch is closed to ground. With CKT 320 grounded, the Exhaust Solenoid is energized allowing the Exhaust Valve to open. The ELC System vents into the atmosphere, lowering the rear of the vehicle. When the vehicle body reaches its original height +/-25 mm (1 inch), the Height Sensor Assembly opens the Exhaust Control Switch, de-energizing the Solenoid and closing the Exhaust Valve.

"LEVEL RIDE" INDICATOR
When the Compressor Motor Relay is energized, voltage is applied through CKT 322 to the "LEVEL RIDE" Indicator bulb. The ground circuit is completed through CKT 1500 to G201. CKT 322 runs in parallel with the Compressor Motor, therefore when the motor receives voltage, the "LEVEL RIDE" Indicator will illuminate.