Location of Suspension leveling compressor is left of engine compartment..
Compressor Relay is in position "E" in the Relay Center.
Relay Center Location under dash panel lower right front corner of
Be sure fuses 9B ( 20 amp) and 5B a (10 amp) are good. They are located in the IP fuse block. Use a 12 volt test lamp to check for power on both sides of these fuses. 9B should have power on both sides at all times. 5B should have power on both sides with Ignition key in Run position.
IP fuse block near parking brake control.
DESCRIPTION The height sensor controls two circuits, compressor relay coil ground circuit and exhaust solenoid coil ground circuit. To prevent energizing the compressor relay and exhaust solenoid circuits during normal ride motions, the sensor circuit provides a predetermined delay before the ground circuit is completed. The sensor electronically limits compressor run time and exhaust solenoid energized time. This limit function is necessary to prevent continuous compressor operation in case of a system leak or continuous exhaust solenoid operation. This timer is reset whenever the ignition is turned Off and On, or height sensor exhaust or compressor signal changes. The height sensor is mounted to the body frame in the rear of the vehicle. The sensor actuator arm is attached to the control arm by a short link.
Level sensor locations.
CAUTION: When diagnostic procedures require that vehicle be raised on a hoist, it is important that the rear axle assembly remains in the normal trim height position at all times. When a frame contact hoist is used, two additional jack stands should be used to support the rear axle or control arms in the normal trim height position.
Check to see if the compressor is receiving a voltage signal. If the power and ground are OK when the compressor is commanded on, and it does not respond, the compressor is faulty.
The compressors may last the entire life of the vehicle, or they can fail in 10 years or sooner.
I hope this information helps