* Grounding Issues: A poor ground connection can prevent the current from flowing correctly to the wiper motor. Check the ground wire connected to the motor and the chassis. Clean any corrosion and ensure a solid connection. There might be multiple ground points related to the wiper system.
* Wiring Harness Damage (Beyond the Replaced Section): You replaced the harness, but damage could exist in other sections of the wiring leading to or from the replaced part. Inspect the entire wiring harness carefully for breaks, chafing, or corrosion, particularly near bends and joints.
* Wiper Motor Relay: The wiper motor is often controlled by a relay. A faulty relay will prevent power from reaching the motor. Locate the relay (usually in the under-hood fuse box or a central junction box) and try swapping it with a known good relay of the same type.
* Multi-Function Switch (Column Switch): Even though you replaced the wiper switch (assuming that's what you meant by "switch"), the problem might lie within the multi-function switch assembly on the steering column itself. This switch controls various functions, and a faulty internal component could be interfering with the wiper circuit. This is a more complex repair.
* Park Switch (Intermittent Wiper System): Some systems have a park switch that tells the wiper system where the wipers are positioned. If this switch is faulty, the system might not operate correctly.
* Body Control Module (BCM): The BCM acts as a central computer controlling many electrical functions. A faulty BCM could be sending incorrect signals to the wiper motor, even if all other components are working correctly. This is a less likely cause but possible.
* Incorrect Installation: Double-check all connections during the replacement process. A simple wiring error can prevent the wipers from working.
Troubleshooting Steps:
1. Visual Inspection: Carefully examine all wiring related to the wipers for any obvious damage.
2. Continuity Test: Use a multimeter to check for continuity in the wiring harness to ensure no breaks in the circuit.
3. Voltage Test: Use a multimeter to check for voltage at the wiper motor connector with the wipers switched on. If there's no voltage, the problem is upstream (before the motor).
4. Relay Testing: Test or replace the relay as described above.
5. Ground Check: Thoroughly clean and check all ground connections related to the wiper system.
If you're not comfortable performing these checks yourself, it's best to take your Windstar to a qualified mechanic for diagnosis and repair. The intermittent nature of electrical issues makes it challenging to pinpoint the cause without proper testing equipment and experience.
