* High Engine Coolant Temperature: This is the most common reason. A sensor detects when the coolant temperature exceeds a certain threshold (typically around 220-230°F or 104-109°C), and the fan activates to draw air across the radiator, dissipating heat and lowering the coolant temperature.
* A/C Operation: The cooling fan often runs when the air conditioning is on. The A/C condenser is located in front of the radiator, and the fan helps to cool the refrigerant in the condenser, improving the A/C's efficiency.
* Low Coolant Level: While less direct, a low coolant level can lead to overheating, triggering the cooling fan. The system might not be able to dissipate heat effectively due to insufficient coolant flow.
* Faulty Sensor: A malfunctioning coolant temperature sensor can send inaccurate readings to the engine control module (ECM). This could cause the fan to run unnecessarily or not run when it should.
* Faulty Fan Relay or Motor: Problems with the fan relay (which switches the power to the fan) or the fan motor itself can cause the fan to run continuously or not at all.
In short, the fan's job is to prevent the engine from overheating. If the fan is running excessively or not at all, there may be an underlying issue that needs attention. A diagnostic scan by a mechanic can pinpoint the exact cause.
