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Radiator Fan Turns On When The Car Starts – What There Is To Know

How To Know When It's Time For A New Radiator Fan

In order to figure out the reasons why your radiator fan turns on when the car starts, you need to know how it works, the function of the radiator fan, and the signs of a failing radiator fan. Knowing this key information can help you keep your radiator fan running efficiently for as long as possible. 

Auto Repairs Are EXPENSIVE


Within your car, there are vital components that directly relate to your car’s smooth running and operation. Without these parts working at the optimal level, your vehicle will not be able to function and perform the way it is supposed to. If your vehicle is not operating the way it is meant to, then the radiator fan will not turn on when the car starts. 


If your car is running at a sub-par level, then there is a greater chance that other components can be negatively affected and lead to more repairs and replacements. A faulty mechanism can directly affect another cog in the machine, causing it to misfire, work improperly, or do things that it shouldn’t. 


One part of the car that is imperative to a smooth and safe ride is the radiator fan. Without the radiator fan working, you will have a miserable time getting between places in your vehicle. The radiator fan is in charge of pulling cool air through the car’s radiator, helping cool off the passengers and keep your ride as comfortable as possible. Let’s find out the function of the radiator fan, the symptoms of a failing radiator fan, and why your radiator fan turns on when the car starts. 

What Is The Function Of The Radiator Fan?

The engine contains a combustion chamber where explosions take place to provide power and heat the car. These explosions cause the engine to heat up extremely quickly and can sometimes lead to overheating. This is a reason why the radiator fan turns on when the car starts. 


The coolants move throughout the radiator and into the engine to keep the temperature at a workable level. The job of the radiator is to keep the coolant at the right temperature so that when it travels back to the engine, it is able to take on more heat, and prevent the engine from getting too hot. 


A radiator fan is imperative in keeping the coolant’s temperature low enough to keep the passengers comfortable. If the radiator fan is not working correctly, your car can get damaged. If you let the radiator fan or car go too long without a repair, the fix can be thousands of dollars out of your pocket. This is a reason why the radiator fan turns on when the car starts. 


  • How The Radiator Fan Works



As soon as you feel like your radiator fan has stopped working or your car isn’t getting cool, you need to take some troubleshooting steps to determine the problem. If you can’t figure it out, take your car to a mechanic right away so he can determine the issue.


The radiator fan is positioned between the radiator and the engine and is in charge of cooling the car and keeping the occupants at a comfortable temperature level. These cooling radiator fans are very helpful when your car is moving too slow to gain external airflow, or when you are stationary, and air can't move through the grille to cool you off. This is a key reason why the radiator fan turns on when the car starts. 


The electric cooling radiator fan, which turns on and off as needed based on the internal vehicle temperature, is an improvement over engine-driven fans that slow down a usually when they are needed the most. A failed radiator fan can result in overheating your engine. 

Two Types Of Radiator Fans 


There are two basic types of radiator fans that will be in your car – either mechanical or electric. The difference between these two kinds of fans can affect why the radiator fan turns on when the car starts.


  • Mechanical


The mechanical radiator fan is generally more common in older, rear-wheel-drive cars. You might also find mechanical radiator fans more often in modern trucks and bigger vehicles. Most of these radiator fans have a built-in clutch, allowing the fan to idle when the engine is cold, saving some energy and power for an efficient mechanism.


The built-in clutch will also be smart enough to rotate when it is hot in the car, being able to detect the temperature and when to operate. Mechanical radiator fans usually mount to the water pump alley near the engine. 


  • Electric


This type of radiator fan is almost always found in modern vehicles and sedans. The electrical radiator fan is controlled by an electric motor, with the radiator fan turns on when the car starts. The engine’s computer is in charge of when the fan turns on and off, dictating the radiator fan’s usage based on the temperature of the vehicle. 

Troubleshooting Your Radiator Fan


If you prefer to do some of the work yourself to save some money, you can actually troubleshoot a cooling fan to see where the problem lies and how to fix it. There are typically a few locations where the problem is originating from, such as the fan motor, thermal switch, wire, or relay. 


  • Test If Your Radiator Fan Has Actually Failed 



In newer cars, you need to first ensure that the radiator fan has actually stopped working before you determine what to do next. You can do this by listening and feeling if the radiator fan turns on when the car starts. If you need to confirm if it’s in working order or not, you should turn on your engine and let your vehicle idle. Turn the air conditioning to the maximum setting – this should spark the cooling fan to immediately come on.


This typically takes about 15-20 minutes for the engine to reach the right temperature for the radiator fan to turn on in older cars. If there’s a problem with the engine’s temperature, then this can damage the radiator. Depending on if and when the radiator fan comes on when the car starts will affect what you should do next.


If the fan doesn’t come on, you need to look for a broken fuse or breaker. In older cars, you might have a fusible link – this is wire within an insulated block of rubber. If the wire stretches, the wire link could be broken, and you’ll need to replace it. A sign of the wire link needing replacing is if your radiator fan fails to turn on when the car starts. 


  • Test The Radiator Fan Motor



If your fan has still failed to turn on when the car starts, you can check the fan by connecting a power source to it. Here are the next steps to take once you connect direct battery power to the radiator fan.


First, you need to unplug the wiring connector. Check for any damage and clean the connector to get rid of any debris or contaminants. Ensure that the wires are firmly attached and are not damaged.


Second, look at the wires and identify which ones are power wires and which ones are ground wires to avoid any confusion.


Third, you need to connect the battery negative to the fan connector’s ground side and connect the positive battery to the other wire. You may need to look at your vehicle repair manual to see if your vehicle has a 4-wire terminal or three terminals, with two for power and one for ground wires. 


Lastly, after you connect the radiator fan to your battery, the radiator fan should turn on when you start your car. 


  • Check All Wires And Connectors 



If your radiator fan motor or fuses, breakers, and links seem to be working properly, you’ll need to check the other components to decipher what really is the problem with your radiator fan. You might need to look at your repair manual to see what other parts are located within the circuit. 


  • Test The Radiator Fan Temperature Switch 



The temperature switch in most vehicles is typically located by your car’s engine computer or your powertrain computer. For this test, the only tool that you need is a test light to see why your radiator turns on when you start your car. 


First, you need to connect your test light to the battery ground. Second, start the engine and start idling your vehicle. Back probe the connector terminals with the test light – hopefully, one of the connector terminals is able to turn on the test light and show that it is working properly.


Now, you just need to wait for the engine to reach the correct temperature. After the engine has reached operating temperature, you have to probe the other wire at the connector. If the light doesn’t come on, you figured out that the switch is not working. 

Symptoms of a Bad or Failing Radiator Fan


After noticing during the radiator fan inspection that something is wrong with your radiator fan or fan clutch, you now know you need to get a replacement. You can always tell that something is wrong with your radiator fan not turning on when you start your car. In addition, there are other obvious signs of a bad or failing fan motor. However, if you are able to notice the telltale signs and symptoms of a bad or failing radiator fan motor, you might be able to stop the problem before it gets worse.


  • The Cooling Radiator Fan Does Not Come On



The most common symptom of a faulty cooling radiator fan motor is that the cooling fan does not come on when you start the car. If the cooling fan motor burns out, the cooling fans will then, in turn, be disabled. Since the cooling fan motors work in tandem with the fan blades to pull air through the radiator, the blades will then not be able to spin or cause any airflow to cool off the car. 


  • Vehicle Overheating



The second symptom of a damaged radiator fan motor is that your car is currently overheating. The cooling fans are designed to turn on once a certain temperature has been reached inside of your vehicle, or certain conditions have been met. If the cooling fan is failing or damaged, the engine temperature will continue to rise, and eventually overheat. 


Engine overheating could also result from other problems, so be sure to have your vehicle diagnosed by a professional before assuming it is your radiator fan.


  • Blown Fuse



If your cooling fan circuit fuse has blown, this is another sign of a problem with the radiator fan motors. If your motors fail or surge unexpectedly, then this can cause the fuse to blow. The fuse will blow to protect the rest of the system from further damage due to the unforeseen electrical surges. 


The cooling fan motors are crucial to the cooling fan assembly and play a huge role in your car’s safety, keeping the correct temperatures while idling and at low speeds. Since the radiator fan motors are so important, you need to bring your car to a professional technician to diagnose and repair your parts to keep your vehicle safe and working conditions. 



The radiator fan is a crucial part of your car that is in charge of cooling the car and keeping the occupants at a normal temperature level. These cooling radiator fans are very imperative to when your car is running slowly or sitting still, as external airflow will not be able to move through the grille and cool-off the passengers.


By figuring out the signs and symptoms of a failing radiator fan or fan motor, you can prevent the radiator fan from breaking down, and ensuring that the radiator fan turns on when you start the car. 

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