1. Safety First:
* Disconnect the battery: This prevents accidental shocks and shorts while working on the electrical system.
2. Identify the Problem:
* Does *nothing* work? (No movement in any direction) This points towards a power issue (fuse, wiring, motor).
* Does *some* movement work? (e.g., forward/backward but not up/down) This suggests a problem with a specific motor or its wiring.
* Intermittent operation? This often indicates a wiring or connection problem.
* Unusual noises? Grinding, clicking, or humming might point to a failing motor or gear.
3. Check the Easy Stuff First:
* Fuses: Consult your owner's manual to locate the power seat fuse(s) and check them with a multimeter or by visual inspection (blown fuses will have a broken filament). Replace any blown fuses.
* Power Seat Switch: Try different switches if your Expedition has multiple seats with power adjustments. If you have a spare switch, try swapping it in to rule this out. A faulty switch is a common cause.
* Wiring Connections: Inspect the wiring harness connected to the power seat motor and the switch. Look for loose, broken, or corroded connections. Clean or repair as needed. This is often under the seat.
4. More Involved Troubleshooting:
* Motor Test (Advanced): If you have a multimeter, you can test the power seat motor itself for continuity and to check if it's receiving power. This requires some electrical knowledge and should only be attempted if you're comfortable with it. Incorrectly testing can damage the motor or your tools.
* Internal Seat Mechanism: If the motor seems fine, the problem could be within the seat's internal mechanism itself – gears, cables, or linkages. This requires removing the seat to access these parts and may necessitate replacing parts or seeking professional help.
5. Seeking Professional Help:
If you're not comfortable working on electrical systems or mechanical components, it's best to take your Expedition to a qualified mechanic or an automotive electrician. They have the tools, expertise, and parts to diagnose and repair the problem efficiently.
Specific to 1999 Ford Expedition:
* Owner's Manual: Your owner's manual is your best resource for fuse locations and diagrams.
* Online Forums: Search online forums (like Ford Expedition forums) for similar issues. Someone may have encountered the same problem and shared a solution.
* Repair Manuals: A Haynes or Chilton repair manual for your vehicle can provide detailed diagrams and instructions.
Remember, working with car electrical systems can be dangerous. If you're not comfortable with electrical work, it's always best to leave it to a professional.
