When Does the Car Radiator Fan Turn On?

When Does the Car Radiator Fan Turn On? – Electrical system problems seem very trivial. Moreover, someone, for example, knows that the problem is a connector that has a rusty problem. Or most simply, it turns out that only a broken or burned fuse. Instead of thinking that finding the cause is complicated, they will say ‘ah, that’s it!’. This may also apply to the problem of why the radiator fan can turn on.

This time we will try to discuss the reasons behind turning on the radiator fan in your car. You may have noticed that the radiator fan is not running all the time. Obviously, this is not an older fan that uses a v-belt to connect the radiator fan pulley to the crankshaft pulley. Yes, this is an electric fan that is in every modern car today. There are many conditions that are required for an electric radiator fan to be actively working. Well, in this article, I try to peel it completely.

Read more: 5 Causes of RPM Drops when AC is On and the Solution

When Does the Car Radiator Fan Turn On?

We know that today’s cars use electric radiator fans that only run for a certain time. This is different from previous cars whose fans automatically turn when the engine is running. The fan rotation follows the engine speed. If the engine spins fast, the radiator fan will spin fast, and vice versa. For the cooling system, such a mechanism is not optimal for achieving the engine cooling objective.

Then why do car engines now use electronic fans? It turned out to be aimed at increasing the efficiency of engine performance. Why is that so? That’s because the engine can work optimally not at low temperatures but at working temperatures. The working temperature of the machine ranges from 70 to 90 degrees Celsius. To keep the engine working at that temperature, the usual radiator fan mechanism is not good enough.

Simply put, the radiator fan that sometimes turns on and sometimes turns off has the purpose of keeping the engine temperature at its working temperature. But not only that, because in fact when the AC is turned on the fan immediately turns on even though the engine temperature is still cold.

Car Radiator Fan Turn On
Sensor, ECU, and Radiator Fan Connection – Car Radiator Fan Turn ON.

So broadly speaking, the radiator fan will turn on when it finds two conditions, namely when the engine temperature is hot and when we turn on the AC system. Then why the radiator fan only turns on when conditions like that? see the explanation below.

1. When the engine temperature exceeds its working temperature.

Maybe you already know that the ‘computer’ nowadays controls all the systems on the car. And the reality is, it’s true. The computer plays a role in three parts, namely input, controller, and output. Components that go into the input are sensors, including sensors that detect the temperature of the cooling water.

The controller component is the ECU (engine control unit) or the car’s processor. Meanwhile, the output components include all types of actuators such as injectors, coils, and radiator fans.

Read more: ECM vs PCM vs ECU what are the differences?

As I said above, the radiator fan will turn on when the engine temperature is hot. So how do you know the engine temperature is hot? That is the job of the ECT (engine coolant temperature) sensor.

Car Radiator Fan Turn On
How Does the Radiator Fan Turn On Based on the ECT Sensor?

ECT Sensor Working, Radiator Fan On

The mechanism, the ECT, which is a thermometer-type sensor, is in the cooling water flow at the engine output hose. This type of thermometer sensor is sensitive to heat. So the sensor will work based on the coolant radiator temperature. The ECU sensor will send the data to the ECU. Through the system, the ECU will process the data to estimate the engine temperature value.

If the engine temperature exceeds 90 degrees Celsius, the ECU will activate the radiator fan at low speed. Then, when the engine temperature drops to 80 degrees Celsius, the ECU turns off the fan again. However, when the temperature does not decrease or even increase, the ECU will accelerate the rotation of the radiator fan.

Read more: 5 Common Signs of Bad Radiator Cap

That’s why you usually hear the hum of a different fan, sometimes the hum of the fan sounds soft, and sometimes it’s quite loud.

The purpose of this mechanism is to keep the engine temperature at a temperature of 80 – 90 degrees which is the most optimal temperature to get efficient engine performance. Efficient means there is a balance between the power produced and the economical use of fuel. If the engine temperature is lower, the fuel tends to condense and is difficult to blend with the air so the effect is more wasteful, while higher temperatures (than working temperature) can cause the engine to overheat.

2. When the car air conditioner is in the ON position

The second thing that causes the radiator fan to spin is because of the car air conditioner. Maybe ordinary people are still confused, what is the relationship between the radiator fan and the car air conditioner? Aren’t they two different sensors? One is the car engine and the other is the cabin circulation system.

Car Radiator Fan Turn On
Air Conditioner vs Radiator Fan – Car Radiator Fan Turn On.

Maybe you already know that the AC system has a condenser component that functions to cool the refrigerant or freon. It turns out that this condenser is located in front of the radiator. In other words, in addition to cooling the radiator, the radiator fan also functions to cool the freon in the condenser.

Therefore when the radiator fan will turn on when the AC is on. The fan is not actually cooling the radiator but is cooling the condenser. But even though the car air conditioner is turned on, it doesn’t mean the fan continues to spin as long as the AC is in the ON position.

The radiator fan also spins occasionally. It is the same as a radiator that is cooled when the temperature exceeds 90 degrees. The condenser is also cooled according to the AC temperature the driver wants.

Read more: Causes of AC Not Cold when the Car is Stopped

If the driver is setting the temperature to medium, the fan only runs infrequently at a relatively low speed. However, if the driver sets a low AC temperature, the fan will spin longer at a higher speed.

The mechanism also involves sensors, controllers, and outputs as is the case with radiators. But in this case, the sensors used are refrigerant pressure sensors (sensors that detect AC freon pressure) and AC air temperature sensors.

What happens when the car’s AC keeps spinning?

That’s a sign there’s a problem. However, the problem is not only on the electrical side. The problem could be because the freon circulation is blocked so that the freon pressure is always high detected. This will trigger the fan to run continuously.

Another thing is when the cooling water volume is very less. That will cause overheating so the radiator fan will rotate continuously.

So when you have a problem with this electric fan spinning continuously, first check the non-electrical part. For problems involving engine electrical, usually the check engine light will come on. And to find out the problem, you need to do a scan engine using the scan tool.

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