top of page

Is a Car Radiator Fan Always On? (Explained)

A car radiator fan plays a crucial role in the cooling system of your vehicle. It helps to dissipate the heat generated by the engine, ensuring that the coolant remains at a consistent temperature and the engine doesn't overheat.


A car radiator fan is temperature controlled, meaning it comes on if the coolant temperature is high and turns off if it is optimal or below its target temperature. Usually, a radiator fan that is always on has an issue.


In this article, we'll delve into the details of radiator fans and answer the question of whether a car radiator fan is always on.

 

Table of Contents:


a car radiator fan and shroud on the floor

What Does a Car Radiator Fan Do?

The radiator fan is responsible for drawing air through the radiator to cool the coolant. The coolant absorbs the heat from the engine and transports it to the radiator.


As the coolant flows through the radiator, the fan blows air over the fins of the radiator, helping to dissipate the heat and bring the coolant temperature down.


Is a Car Radiator Fan Always On?

No, a car radiator fan is not always on. It is temperature controlled, meaning it only comes on if the coolant temperature is high and turns off when it reaches its optimal or target temperature.


When Should Your Radiator Fan Be On?

The radiator fan should come on when the coolant temperature reaches a certain level, usually around 220-230 degrees Fahrenheit (104-110 degrees Celsius). This temperature is known as the thermostat's "open" temperature.


When the thermostat opens, it allows the coolant to flow through the radiator, where it can be cooled by the fan.


The fan will continue to run until the coolant temperature drops to the thermostat's "closed" temperature, usually around 195-205 degrees Fahrenheit (91-96 degrees Celsius).


a car radiator fan up close

Should the Radiator Fan Come on When a Car Starts?

In most cases, the radiator fan should not come on when the car is first started.


The fan is designed to cool the coolant, which takes time to warm up. As a result, the fan will typically not come on until the coolant temperature reaches the thermostat's open temperature.


If the radiator fan is coming on when the vehicle starts there may an underlying issue.


Is It Normal for Radiator Fan to Stay On?

No, it is not normal for the radiator fan to stay on. If the fan is always on, it could indicate a problem with the cooling system.


Possible issues include the following.


  • A faulty thermostat

  • Malfunctioning radiator fan relay

  • Faulty coolant temperature sensor

  • Malfunctioning ECU

  • Wiring issues (short circuits, damaged wiring, etc.)


It is important to have these issues addressed as soon as possible.


How Do I Know if My Radiator Fan Is Working?

To test if your radiator fan is working properly, you can do the following.


  1. Listen for the fan to come on when the engine reaches operating temperature.

  2. Turn on the AC (air conditioning). In some vehicles the radiator fan comes on by default when the AC is switched on.


Conclusion

A car radiator fan is temperature controlled and only comes on when the coolant temperature is high. If the fan is always on, it could indicate a problem with the cooling system.


It is important to have any issues with the radiator fan addressed as soon as possible to avoid engine overheating.