The first and most common reason for a cooling fan light to come on but for the car not to overheat is a low coolant level. When the coolant level is low, the coolant temperature sensor may not be fully submerged in coolant, which can cause it to send a false signal to the engine control unit (ECU) that the engine is overheating. The ECU will then turn on the cooling fan to try to cool the engine, even though it is not actually overheating.
Faulty Coolant Temperature Sensor
Another possible cause for a cooling fan light to come on but for the car not to overheat is a faulty coolant temperature sensor. The coolant temperature sensor is responsible for sending the engine temperature to the ECU. If the sensor is faulty, it may send a false signal to the ECU that the engine is overheating, even though it is not. The ECU will then turn on the cooling fan to try to cool the engine, even though it is not actually overheating.
Faulty Cooling Fan Relay
The cooling fan relay is responsible for turning the cooling fan on and off. If the relay is faulty, it may not send power to the cooling fan, even though the ECU has turned it on. This can cause the cooling fan light to come on, but the fan will not actually turn on.
Wiring Problems
Wiring problems can also cause the cooling fan light to come on but for the car not to overheat. For example, if there is a loose or broken wire in the circuit that controls the cooling fan, the fan may not receive power, even though the ECU has turned it on. This can cause the cooling fan light to come on, but the fan will not actually turn on.
Incorrect Thermostat
The thermostat is a valve that regulates the flow of coolant between the engine and the radiator. If the thermostat is faulty, it may not open properly, which can restrict the flow of coolant and cause the engine to overheat. This can cause the cooling fan light to come on, even though the car is not actually overheating.
