1. Safety First: Disconnect the negative (-) terminal of your battery. This prevents accidental shorts and protects you from electric shock while working on the electrical system.
2. Check the obvious:
* Wiper switch: Make absolutely sure the wiper switch is in the "off" position. Sometimes, they can get stuck or malfunction internally. Try wiggling the switch gently while it's in the "off" position.
* Fuse: Check the fuse(s) related to the wipers in the fuse box (under the hood and/or inside the car). A blown fuse would prevent the wipers from working *at all*, but it's worth a quick check. Replace any blown fuses with the correct amperage rating.
3. Inspect the Wiper Motor's Wiring Harness:
* Carefully examine the wiring harness connected to the wiper motor. Look for:
* Loose connections: Wiggle the connector. A loose connection can cause intermittent operation or failure to shut off.
* Broken or frayed wires: Check the wires for any signs of damage. Repair any damaged wires with appropriate connectors or splicing techniques.
* Corrosion: Clean any corrosion you find on connectors with a wire brush and electrical contact cleaner.
4. Testing (requires a multimeter):
This step requires a multimeter capable of checking continuity and voltage. If you're not comfortable working with electricity, have a qualified mechanic perform this test.
* With the battery still disconnected: Use your multimeter to test the continuity of the wires going to the wiper motor. There should be a continuous connection (low resistance) between the relevant terminals. If you find a broken wire, that's your culprit.
* Reconnect the battery (carefully!). With the ignition on and the wipers switched *off*, measure the voltage at the wiper motor connector. There should be virtually zero volts. If you have significant voltage present (even with the switch off), it indicates a short circuit or problem within the switch or relay circuit which is constantly feeding power to the motor. This strongly suggests a faulty switch or relay.
5. Relay testing (if the above tests don't reveal the issue):
The relay is responsible for switching the high current needed to run the wiper motor. Locating the wiper relay in your 2003 Crown Victoria's fuse box will likely require consulting your owner's manual or online resources specific to your vehicle's year and trim level.
* Visually inspect the relay: Look for any signs of damage (burning, melting).
* Swap the relay: If you can easily access and swap the relay with a similar one (same amperage rating), temporarily replace it with one from a less critical circuit (like the horn if possible) to test. If your problem is solved, the relay was faulty.
Conclusion:
If the wiring and the relay are fine, you likely have a faulty wiper motor that's either internally shorted or has a mechanical issue causing it to remain engaged, even though it's receiving no power signal to run. However, given that the wipers won't turn off, the electrical side is far more probable. The process of elimination outlined above should help isolate the problem. If you're not comfortable performing electrical tests, take your vehicle to a qualified mechanic.
