* Faulty Cooling Fan Relay: This is the most common culprit. The relay acts as a switch, activating the fan when the engine needs cooling. A faulty relay might be stuck closed, constantly powering the fan.
* Bad Cooling Fan Control Module (if equipped): Some vehicles, particularly older ones, have a dedicated module that controls the fan's operation. This module could be malfunctioning, sending incorrect signals.
* Short Circuit in the Wiring: A short circuit in the wiring harness leading to the cooling fan or the relay can also cause the fan to run continuously. This could be caused by damage to the wiring, corrosion, or a rodent chewing on the wires.
* Faulty Temperature Sensor: The engine's temperature sensor tells the system when to activate the cooling fan. A faulty sensor might send incorrect signals, leading to the fan running unnecessarily. There are usually two sensors - one for the gauge and one for the computer.
* Faulty PCM (Powertrain Control Module): In more sophisticated systems, the PCM controls the cooling fan. A faulty PCM is less likely but possible. This is a more expensive and complex fix.
Troubleshooting Steps:
1. Check the Relay: Locate the cooling fan relay (usually in the underhood fuse box). Try swapping it with a relay of the same amperage and type for another less crucial system (if possible and safe). If the problem shifts to that other system, you've found the faulty relay.
2. Inspect the Wiring: Visually inspect the wiring harness leading to the fan and the relay for any signs of damage, corrosion, or fraying. Repair or replace any damaged wiring.
3. Check the Temperature Sensor(s): The location of the temperature sensors varies by model year. Consult a repair manual or online resources for your specific vehicle to locate them. You can test the sensor's resistance with a multimeter (compared to specifications found in a repair manual) to see if it's providing accurate readings.
4. Have the System Diagnosed: If you're not comfortable working on the electrical system yourself, take your Sable to a qualified mechanic. They can use a diagnostic scanner to read any trouble codes stored by the PCM which may pinpoint the issue.
Important Note: Continuously running cooling fans can drain your battery. If the problem persists, disconnecting the fan's power (at the relay or wiring harness, but carefully) can prevent further battery drain while you diagnose the problem. However, don't drive the vehicle for extended periods with the fan disconnected, as this could lead to engine overheating.
