* Faulty Fan Relay: This is a common culprit. The relay is an electrical switch that controls the fan. If it's stuck closed, the fan will run continuously regardless of engine temperature.
* Faulty Cooling Fan Control Module (CFM) or PCM (Powertrain Control Module): The CFM (if equipped) or the PCM receives signals from various sensors (like the coolant temperature sensor) to determine when to turn the fan on and off. A malfunction in either could cause the fan to run constantly. The PCM is more likely on a '98 Caravan.
* Short Circuit in the Wiring: A short in the wiring harness leading to the fan or the relay can provide a constant power supply to the fan motor. This could be caused by damaged wires, corrosion, or a chafed wire rubbing against something metal.
* Faulty Coolant Temperature Sensor (CTS): This sensor tells the PCM or CFM the engine's temperature. If it's malfunctioning and providing a falsely high reading, the system might think the engine is overheating and keep the fan running.
* Faulty Fan Motor: While less common, a faulty fan motor might draw current even when it shouldn't be running. This is less likely to be the cause if the fan is just constantly running, as opposed to running intermittently and then seizing up.
Troubleshooting Steps:
1. Check the Relay: Locate the cooling fan relay (usually in the under-hood fuse box or a separate relay center). Try swapping it with a known good relay of the same amperage and rating. If the problem goes away, the relay is bad.
2. Check the Wiring: Visually inspect the wiring harness leading to the fan and relay for any signs of damage, corrosion, or shorts.
3. Check the Coolant Temperature Sensor: This usually requires a multimeter to check its resistance readings against specifications in a repair manual or online. A faulty sensor often leads to erratic fan behavior.
4. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read any stored codes in the PCM. These codes can provide valuable clues about the problem.
5. Consult a Repair Manual: A repair manual specific to your 1998 Dodge Caravan will provide detailed diagrams and troubleshooting steps for the cooling system.
If you're not comfortable performing electrical work, it's best to take your Caravan to a qualified mechanic for diagnosis and repair. Leaving the fan running constantly will drain your battery.
