Freightliner Engine Fan Not Coming On – Causes And Fixes

When you have a freightliner engine fan not coming on, you are up for some serious problems.

After all, the fan is a crucial part of your vehicle’s cooling system. This blows heat off from your radiator fins and makes sure your engine stays at an ideal operating temperature.

So, when your engine fan is not doing its job, this can spell out disaster to your engine. Overheating may occur, and this can snowball into further problems that will ultimately result in an expensive repair.

Normally, you will not hear your fan blowing upon starting the engine and until it reaches the desirable operating temperature. It may take about 5 minutes or so for the fan to kick in, and it depends on the model of your vehicle. But one way to shorten the interval is by putting some load on your engine. 

You may turn the AC on, which can cause the fan to start blowing sooner. However, if you still fail to hear the engine fan coming on, then it indicates a problem that needs to be solved. You need to determine why this is happening and what you can do to address it. Otherwise, your engine is at risk of overheating.

Let’s jump right into it.

freightliner engine fan not coming on

Why Is Your Freightliner Engine Fan Not Coming On

Even with the AC on and a few other loads on the engine, if your engine fan is still not coming on, you may want to take a look at the common reasons why this happens to have a better understanding of the issue and determine the right action to take.

For instance, there may be a faulty temperature switch, a blown relay or fuse, low coolant temperature, or even some damage to your wiring harness. Let’s take a look at these common causes more closely.

1. Blown fuse

Your fuse serves as a shield that protects your electronic and electrical components. Thus, it prevents damage caused by power surges or electric bridges. When there is a current surge that is likely to cause damage to the electrical component, the fuse’s metal strip will cut, which then prevents the flow of power to the key component. However, when you have a broken fuse, this means it is blown and is not doing its job of protecting electrical components.

2. Faulty temperature coolant sensor

Your vehicle has temperature sensors, and these are capable of detecting coolant temperature and enabling them to communicate with your PCM or a separate module. If there are faults to the sensor, your engine control unit is unable to detect when you have a very hot coolant. Hence, it cannot tell when it is supposed to start your radiator fan.

3. Low or zero coolant

When your freightliner engine fan is not coming on, but at the same time there is no overheating happening, it means that you do not have coolant in your reservoir. It happens when your sensors are unable to read the engine temperature. What it does instead is to calculate the amount of heat of your engine coolant.

So when you have a low level of coolant, this fills up the reservoir with air, and the sensor gives false readings. This is why you need to check your coolant level when you observe that your engine fan is not turning on.

4. Blown relay

Your engine fan obtains power from the vehicle’s electric flow, which is why there is a relay that helps to regulate this flow of electricity. But over time, relays can be prone to damage, which prevents them from allowing current to pass to the required components. 

Your relay fuse for the engine fan is found in a fuse box or in another box near your fuse box, right in your engine bay. It helps to check your manual to determine where exactly your relay is found. Then, you can check if there is damage to it.

5. Fan controller module issues

As we have mentioned earlier, there are many manufacturers nowadays that install fan control modules that help to regulate your engine fan. This module may be susceptible to failure because of heat from your engine compartment, or because of dust, debris, and corrosion. So, it is important to check your fan controller module to make sure there is no damage to it.

6. Damage to the engine fan

You may want to check the engine fan and see if there are damages to it. Sometimes, the fan itself may be the culprit, such as the electric motor being unable to spring or there is no power to the fan at all. 

It may also be faulty wiring connections that cause the fan to stop working. So, be sure to check the wiring and see if there are some loose connections or damaged wires.

Your Next Step

Once you have determined why your engine fan is not coming on, then you can start working on taking the right action. It all depends on what causes the problem to perform the best troubleshooting techniques that will resolve the issue.

For instance, if the engine fan is broken, then the only solution you have is to replace it. But it may also be that the blade is the only issue, which means you can replace just this part. But more often than not, it is the motor that is the problem, which means a complete replacement is necessary.

In the case of a broken fuse or relay, you need to check first if these are the components that have failed. Look for signs of damage, and you should be able to get these parts replaced cheaply and quickly.

Make sure the coolant level is also ideal, and that the temperature sensor is working right. If the coolant is the issue, then you only need to top it up. But if you have faulty temperature sensors, then you need to have these replaced.


When you have a freightliner engine fan not coming on, there are many reasons why this happens. So, to troubleshoot the problem, you need to take a look at the actual cause, which will help you determine the best solution to fix the problem.

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