1. Check the Obvious:
* Air Compressor: Listen for the compressor to cycle when you start the engine. It should run for a short time to build pressure. If you don't hear it, it might be faulty, have a blown fuse, or have a wiring problem.
* Fuses/Relays: Check the fuses and relays related to the air suspension system in the fuse box (under the hood and possibly inside the vehicle). Consult your owner's manual for the correct locations.
* Air Leaks: Carefully inspect all air lines, connections, and the air bags themselves for leaks. A hissing sound is a clear indication. Spray soapy water on connections to help pinpoint leaks. Pay close attention to the connection points at the air bags and the compressor. Rotting air lines are common on older vehicles.
* Air Suspension Height Sensors: These sensors tell the system the height of the vehicle. A faulty sensor can prevent the system from functioning correctly.
2. More Advanced Troubleshooting (May require tools):
* Air Pressure Test: Use a tire pressure gauge (or preferably an air pressure gauge suitable for higher pressures) to check the pressure in the air bags. Low pressure indicates a leak or compressor problem.
* Air Compressor Test: If you suspect the compressor is bad, you might need a pressure tester to check its output. You may need a specialized tool for accessing its output.
* Electrical Testing: If you have basic electrical knowledge, you can test the wiring harness for continuity and power going to the compressor, solenoids, and height sensors using a multimeter. This requires carefully consulting a wiring diagram (available online or from a repair manual).
* Air Suspension Control Module: The module controls the entire system. A faulty module can cause the entire system to malfunction. Diagnostics are usually required to test this component.
3. Professional Help:
If you're not comfortable working with the electrical system, air lines, or high-pressure air, it's best to take your Expedition to a qualified mechanic, particularly one familiar with air suspension systems. They have the tools and expertise to diagnose the problem accurately and efficiently.
Possible Causes:
* Blown Air Bags: The air bags themselves can rupture.
* Faulty Air Compressor: The compressor is the heart of the system and is prone to failure.
* Leaking Air Lines/Connections: Small leaks can slowly deplete the air pressure.
* Malfunctioning Control Module (Air Suspension Control Unit): This computer manages the system and can fail.
* Faulty Height Sensors: These sensors inform the system about the vehicle's level.
* Wiring Issues: Corrosion or damage to the wiring can interrupt the system's operation.
* Solenoid Valves (if applicable): These control the flow of air to the air springs.
Remember safety first! Disconnect the battery negative terminal before working on any electrical components. High-pressure air can be dangerous, so exercise caution if you're dealing with the air lines and compressor.
