The clicking sound usually means the starter solenoid is engaging, but it doesn't have enough power to fully crank the engine. This could be due to:
* Low Battery: The most common cause. A weak battery can't deliver the high amperage needed to turn the starter motor. Test the battery voltage (should be around 12.6V when fully charged).
* Corroded Battery Terminals: Clean the battery terminals and cables. Corrosion restricts current flow.
* Faulty Starter Motor: The starter itself might be worn out or internally shorted.
* Faulty Starter Solenoid: The solenoid is the electromagnetic switch that engages the starter motor. A faulty solenoid will click but not engage the starter.
* Faulty Ignition Switch: Less common, but a failing ignition switch could also prevent sufficient power from reaching the starter.
* Wiring Issues: A broken or corroded wire in the circuit between the battery, ignition switch, and starter can also cause this.
What to do:
1. Check the Battery: Test the battery voltage and visually inspect the terminals for corrosion. Clean them if necessary. If the voltage is low, charge the battery or replace it.
2. Try Jumping the Battery: If you have jumper cables and another vehicle, try jump-starting the Expedition. If it starts, the problem is likely the battery or charging system.
3. Listen Carefully to the Click: Is it a single click, or multiple rapid clicks? Multiple clicks often point to a low battery. A single, solid click might indicate a problem with the solenoid or starter itself.
4. Have it Professionally Diagnosed: If the problem persists after checking the battery and terminals, it's best to have a mechanic diagnose the issue. They have the tools to test the starter, solenoid, and the electrical circuit.
Ignoring the problem could leave you stranded, so it's important to get it checked out soon.
