Before you start:
* Identify the problem: Is the starter *completely* dead (no click, nothing)? Do you hear a click but no crank? A faint click might indicate a low battery, a bad connection, or a weak starter motor. A clicking sound often points towards a relay or solenoid issue, but not necessarily *the* starter relay.
* Safety first: Disconnect the negative battery cable before working on any electrical components.
Locating the Relays:
The 1997 Ford Expedition's relays are typically located in several places:
* Under the hood: There's a fuse/relay box under the hood, often near the battery. This is the most likely location for relays related to the starter. The specific relay will be labeled or you might find a diagram on the fuse box cover. *However*, there's no guarantee the starter's relay is housed here in a single unit. It could be integrated within the Powertrain Control Module (PCM) circuitry.
* Inside the passenger compartment: Some relays might be found inside the vehicle, usually under the dashboard.
Troubleshooting Steps (More Important than Just Replacement):
1. Battery Check: Make sure your battery has sufficient charge. Test the voltage. A low battery voltage will prevent the starter from engaging even if the relay and starter are good.
2. Battery Cables: Inspect the battery cables for corrosion or loose connections. Clean and tighten them if necessary. This is a very common cause of starting problems.
3. Starter Solenoid: The starter solenoid is part of the starter motor itself and is frequently the culprit. A clicking noise often indicates a problem here. This usually requires starter motor replacement or repair.
4. Wiring: Visually inspect all wiring connected to the starter, battery, and relays for damage or loose connections.
5. PCM (Powertrain Control Module): The PCM controls many aspects of the starting system. A faulty PCM can prevent the starter from engaging, even if all other components are good. This is a more complex diagnosis and often requires a professional scan tool.
If you've ruled out the above and strongly suspect a relay:
1. Identify the relay: Consult your owner's manual or a wiring diagram for your specific Expedition model to locate the starter relay (if it's a dedicated separate unit). The diagram should show the relay's location and function.
2. Visual inspection: Check the relay for any visible damage (burned contacts, etc.).
3. Relay replacement (if needed): If you find a bad relay, replace it with an identical one. *Use the correct amperage relay*. The relay should be clearly labeled with its amperage.
Important Notes:
* Professional help: If you're not comfortable working with car electrical systems, take your Expedition to a qualified mechanic. Incorrect work on the electrical system can cause further damage.
* Wiring Diagram: A wiring diagram is essential for proper diagnosis and repair. You can find these online through various auto repair resources (some are free, some require a subscription).
This detailed response aims to guide you through a proper troubleshooting process rather than just giving a simple, potentially inaccurate, answer. The starting system in a vehicle is complex, and jumping to relay replacement without proper diagnosis can be wasteful and potentially unsafe.
