* Faulty Radiator Fan Relay: This is the most common cause. The relay acts as a switch, and if it's stuck closed, it'll keep power flowing to the fan regardless of the ignition status. Replacing the relay is relatively inexpensive and easy.
* Short Circuit in the Wiring Harness: A short circuit in the wiring leading to the fan or the relay can provide a constant power source. This can be difficult to diagnose and requires careful tracing of the wiring. Look for any damaged or frayed wires near the radiator, fan, and relay.
* Faulty Temperature Sensor: While less likely to cause the fan to run *constantly* after the key is off, a malfunctioning coolant temperature sensor could send a false signal to the fan's control module, even if the engine is cool. A faulty sensor might remain "hot" in its readings.
* Problem with the Fan Control Module (PCM or similar): The PCM (Powertrain Control Module) or a dedicated fan control module might be malfunctioning and sending the wrong signal even when the ignition is off. This is less common but possible.
* Aftermarket Accessories: If you've added any aftermarket accessories recently, their wiring might be interfering with the fan's circuitry.
* Stuck Thermostat: While unlikely to directly cause the fan to run constantly with the key off, a stuck thermostat in the fully open position could lead to higher engine temperatures, potentially triggering the fan even when the engine is cool and the key is off.
Troubleshooting Steps:
1. Check the Radiator Fan Relay: Locate the relay (consult your owner's manual for its location). You can try swapping it with another relay of the same amperage (if you have one readily available). If the problem goes away, the relay is faulty.
2. Inspect the Wiring: Carefully examine all wiring connected to the radiator fan and relay for any damage, corrosion, or loose connections. Repair or replace any damaged wiring.
3. Check the Coolant Temperature Sensor: This requires a multimeter to check if the sensor is providing the correct resistance readings at different temperatures.
4. Have it Professionally Diagnosed: If you're not comfortable with electrical work, take your Caravan to a mechanic or auto electrician. They have the tools and expertise to diagnose the problem accurately.
Safety First: Remember to disconnect the battery's negative terminal before doing any electrical work on your vehicle to prevent accidental shorts and injury. If the fan continues to run, it could drain your battery.
