Possible Causes:
* Stuck Relay: The relay that controls power to the wiper motor might be malfunctioning and sticking in the "on" position. Heat can cause relays to stick.
* Faulty Wiper Switch: The switch on your steering column might be defective, sending a continuous signal to the wiper motor even when you've turned the wipers off.
* Wiring Issues: A short circuit or damaged wire in the wiring harness leading to the wiper motor or switch could be causing the constant power. This is less likely if it only happens when the car is running.
* Body Control Module (BCM) Problem: The BCM is a computer that controls many functions, including the wipers. A malfunctioning BCM could be sending incorrect signals. This is less likely but possible.
* Park/Neutral Switch: If your wipers are linked to this switch in some unusual way (less common in most vehicles), a malfunctioning switch could trigger the wipers.
Troubleshooting Steps (in order of easiest to hardest):
1. Check the Wiper Switch: Carefully examine the wiper switch on your steering column. See if it feels loose, sticky, or if there's any visible damage. Try wiggling it gently to see if the wipers react erratically.
2. Locate and Inspect the Wiper Motor Relay: Consult your vehicle's repair manual to find the location of the wiper motor relay. It's usually in the fuse box under the hood or inside the cabin. Visually inspect the relay for any signs of burning or damage. You might try swapping it with a relay of the same amperage and rating from another circuit (if possible and safe - don't swap relays if you're unsure).
3. Check Fuses: While less likely to be the sole cause of the constant running, check the fuses related to the wipers in your fuse box. A blown fuse would prevent the wipers from working at all, but a partially blown fuse could cause intermittent or stuck-on behavior.
4. Wiring Inspection (Advanced): This requires some electrical knowledge and is best left to a professional unless you're comfortable working with car wiring. You would need to trace the wiring from the switch to the motor, looking for any breaks, shorts, or corrosion.
5. Body Control Module (BCM) Diagnosis (Advanced): This also requires professional-level tools and diagnostics. A scan tool would be necessary to check for BCM error codes related to the wiper system.
Important Notes:
* Safety First: Always disconnect the negative battery cable before working on any electrical components in your vehicle.
* Repair Manual: A repair manual specific to your year and model Windstar is invaluable for this type of troubleshooting. It will show you the location of components, wiring diagrams, and fuse/relay information.
* Professional Help: If you're not comfortable performing electrical repairs, take your Windstar to a qualified mechanic. Continuing to drive with the wipers constantly running could damage the motor or other components.
The most likely culprits are a faulty wiper switch or a stuck relay. Start with the simpler checks (switch and relay inspection) before moving onto more advanced troubleshooting.
