1998 Ford Expedition Ford Expedition

Tiny
GAELAN
  • MEMBER
  • 1998 FORD EXPEDITION
  • V8
  • 4WD
  • AUTOMATIC
  • 270,000 MILES
My 98 expedition sags in the rear. This problem has just occured. I also notice that the compressor no longer runs. Where should I start to fix the problem?
Saturday, December 13th, 2008 AT 1:14 AM

1 Reply

Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
You will need to have the cars computer read to find the exact location of the fault?

OPERATION
Both air suspension systems are operational with ignition switch in RUN position and have limited operation for 40 minutes after ignition is turned off. The air suspension switch, located under glove box in right kick panel, must be turned off when vehicle is being hoisted, towed or jump-started.
Air suspension warning light is located in instrument cluster. Warning light stays on when air suspension is turned off or a system malfunction is detected.
Air required for leveling vehicle is distributed from air compressor to front and rear fill solenoids through nylon air lines. Front air system can be pneumatically separated from side to side by control module activation of front gate solenoid. This separation provides vehicle stability during roll conditions.
For safety during loading and unloading, vehicle height is memorized and maintained when any door is opened. Vehicle will return to commanded height when doors are closed or vehicle speed exceeds 10 MPH.
AIR COMPRESSOR ASSEMBLY
The air compressor assembly consists of an air compressor and vent solenoid. Neither is serviceable. The air compressor assembly is located on right side of engine compartment between windshield washer reservoir and headlight. The air compressor is powered through a relay, which is controlled by air suspension control module.
Pressurized air from the compressor passes through a drier containing a drying agent. Moisture is removed from the drier when vented air passes out of system during vent operation. Drier may be replaced separately.
AIR COMPRESSOR RELAY
Air Compressor Relay is mounted on bracket near right headlight. Relay, solid state type controlled by the air suspension control module, provides high current flow required to operate air compressor motor.
AIR SUSPENSION CONTROL MODULE
Air suspension control module may also be referred to as simply control module or 4 Wheel Air Suspension (4WAS) module. Air suspension control module is located behind right center of instrument cluster panel. Module controls air compressor and all system solenoids. Control module also provides power to height sensors. Control module outputs are controlled by monitoring height sensors, Vehicle Speed Sensor (VSS), steering sensor, acceleration input, door ajar signal, 2 transfer case signals (on 4WD models) and brake switch feedback signals. Control module conducts all fail-safe strategies and incorporates self-diagnostic and communication capabilities.
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Saturday, December 13th, 2008 AT 6:21 AM

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