Expedition 4WD V8-4.6L SOHC VIN W (1999)
Ride Height Sensor: Description and Operation
Two height sensors are mounted on the vehicle. The sensors send a voltage signal to the air suspension control module. The output ranges from
approximately 4.75 volts at minimum height (when the vehicle is low or in full jounce) to 0.25 volts at maximum height (when the vehicle is high or
in full rebound). The sensors have a usable range of 80 mm (3 inch) compared to total suspension travel of 200-250 mm (8-10 inch) at the wheel.
Therefore, the sensors are mounted to the suspension at a point where full suspension travel at the wheel is relative to 80 mm (3 inch) of travel at the
height sensor. The front height sensor upper socket is attached to the frame bracket at the upper control arm mounting area and the lower height sensor
socket is attached to the upper control arm bracket. The rear height sensor is attached between the No. 5 frame crossmember (upper socket) and the
panhard rod (lower socket). Replace a sensor as a unit.
When the height sensor indicates that the vehicle is lower than trim under normal driving conditions, the air compressor will turn on and pump
compressed air to the system. When the sensor indicates that the vehicle is raised above trim under normal driving conditions, this will cause the air to
be vented from the system to lower the vehicle to its trim height level.
