1. Check the Obvious:
* Is the key working in the lock cylinder? Try lubricating the lock cylinder with graphite or a specialized lock lubricant. If the key feels sticky or doesn't turn smoothly, this is likely the culprit. A broken key or worn lock cylinder might require replacement.
* Is the power to the rear door lock functioning? If you have power locks, check your interior fuse box for a blown fuse related to the rear door locks.
* Are the interior door release mechanisms working correctly? Try manually unlocking the door from the inside using the interior handle. If this doesn't work, the problem is likely *not* in the exterior locking mechanism.
2. Investigate the Wiring:
* Inspect the wiring harness: The wires running from the door to the body can get pinched, frayed, or corroded, especially where the wires flex as the door opens and closes. Carefully inspect the harness for damage. Look particularly at the rubber boot where the wires enter the door.
* Check the actuator: The power lock actuator is a small motor inside the door that moves the locking mechanism. If power is getting to the actuator, you should hear a faint click or motor sound when you try to unlock it. If you don't, the actuator may be faulty and need replacing. Accessing the actuator typically requires removing the interior door panel.
* Test the actuator with a multimeter (advanced): If you're comfortable working with electricity, you can use a multimeter to test the power and ground reaching the actuator. You'll need to consult a wiring diagram for your Windstar to identify the correct wires.
3. Mechanical Issues:
* Rods and linkages: The mechanism connecting the lock cylinder to the actual latch can become disconnected, bent, or broken. This requires carefully inspecting the linkage inside the door. You may need to remove the interior door panel to access it.
* Latch mechanism: The latch itself can become worn or jammed, preventing the door from opening. Again, access to the mechanism requires removing the interior panel.
* Vacuum system (if equipped): Some models used a vacuum system for locking. Check for leaks in the vacuum lines. This is less common on the 1998 but worth investigating if other solutions fail.
4. Seek Professional Help:
If you're not comfortable tackling this yourself (especially the wiring and mechanical aspects), take your Windstar to a qualified mechanic or locksmith. They'll have the tools and expertise to diagnose the problem accurately and perform the necessary repairs.
Before you start:
* Consult a repair manual: A Haynes or Chilton repair manual for your 1998 Ford Windstar will be invaluable. It will provide diagrams and detailed instructions for accessing and repairing the components mentioned above.
* Disconnect the battery negative terminal: This is crucial for safety when working with electrical components.
Remember, safety first. If you're unsure about any step, don't hesitate to seek professional help. Improper repairs can lead to further damage or injury.
