Thermal Fan Clutch vs. Non-Thermal: A Comparative Guide

As summer approaches, driving a car under scorching sun can force the engine to overheat soon. In this intense heat, a vehicle’s cooling system ensures the engine remains cool. Now, the fan clutch is at the center of the system. But I guess you know that you can find two types of fan clutches. In this blog, I will talk about thermal fan clutch vs. non-thermal one.

Well, the main difference between these fan clutches is how they operate. A thermal fan clutch depends on the changes of engine temperature. In short, when the engine is hot, and the clutch engages, it causes the fan to spin faster and cool the engine down. Otherwise, a non-thermal fan clutch operates regardless of temperature fluctuations. It runs at a constant speed or is electronically controlled.

I hope I haven’t made things complex yet. If it appears tough to understand, I suggest you complete reading this blog. Once you finish reading, you will get fan clutches and their differences simpler to pick between them easily. So, share some moments!

Function of Thermal Fan Clutches in Automotive Systems

Thermal fan clutches are temperature-controlled devices. They allow the fan to operate at low speeds and disconnect at higher rates. Through its function, it helps the cooling system and engine use efficiently.

According to On All Cylinders, this clutch reacts to under-hood temperatures. When hot air blows across the radiator, it makes a thermal, bi-metallic spring hot. Then, this hot spring turns and allows valve ports to open within the clutch.

There is a reservoir storing silicone fluid. When the valve ports open, this fluid enters the functional area of the fan clutch. It engages the device and drives the fan. The air from the fan cools down the engine.

Once the engine is totally cool, the spring rotates back. Then, the valve ports are shut off, and it disengages the fan. Through this way, you can get your vehicle engine cool.

You can find versatile types of thermal fan clutches. They offer distinct performance, fit, and appearance of the original equipment clutch it replaces (source).

Function of Non-Thermal Fan Clutches in Automotive Systems

Many people know these clutches as torque-limiting clutches. It is a hint that this clutch can limit the torque.

According to On All Cylinders and It Still Runs, non-thermal clutch operates differently from thermal ones. It does not have any thermostatic valve. Instead, it works on the centrifugal pressure between the housing and the clutch hydraulic coupling. In other words, it works primarily depending on the shaft speed of the water pump.

The non-thermal fan clutch is designed to maintain a consistent fan speed. But it has no relation to the temperature changes of any engine. Moreover, it allows the fan blade to turn at almost a 1:1 ratio at low and idling speeds. Sounds complex? Let me make it clear. It means that the water pump shaft directly drives the fan. So the fan can work at full speed without loading the engine.

Next, the centrifugal force disengages the clutch when the engine speed increases. At this point, the fan is no longer driven by the engine. Also, its speed is determined by the air flowing through the vehicle rather than the engine’s RPM. In this way, the non-thermal clutch cools down the engine.

Usually, non-thermal fan clutches decrease the maximum fan speed to 1200-2200 rpm. Though they reduce torque, using them in your cars can get a better lifespan.

Advantages of Thermal Fan Clutches

In this part, I will discuss the benefits of using thermal clutches in vehicle engines.

Energy Efficiency

Thermal fan clutches adjust their operation based on the engine’s temperature. For instance, the fan runs slower when the engine is cold. It reduces energy consumption and increases fuel economy. On the other hand, the fan runs faster in a heated machine. It provides more cooling power.

Engine Cooling

As I said, the thermal fan clutch operates dynamically. It allows the clutch to run the fan. Hence, the fan’s speed remains lower when the engine is cold—similarly, the rate increases as the engine turns hot. The whole process ensures better engine cooling to prevent overheating. Besides, it can increase the lifespan of your car’s engine.

Engine Efficiency

Thermal fan clutches maintain high engine RPMs by reducing the load when the fan is not used. You can save fuel and get increased engine efficiency.

Advantages of Non-Thermal Fan Clutches

Is there any benefit of using non-thermal fan clutches? I guess the “non” prefix hasn’t made your mind pessimistic about these clutches. For sure, you will get several benefits like thermal ones.

Lower Cost

If you want to save money, you should select the non-thermal fan clutches. Usually, these clutches have simple designs without any need for advanced technology. Besides, they are continuously engaged and turn at 30-60% of the pump shaft speed (source).

Steady Cooling Airflow

The steady flow of cooling air keeps the engine cool under heavy loads. Suppose you have high-performance vehicles. In these vehicles, the engine generates serious heat when you accelerate more. In such conditions, non-thermal clutches are more valuable.

Reduced Load on the Engine

You can reduce the engine load by using non-thermal clutches. Let me explain it. In these clutches, the engine does not continuously drive the fan. Instead, the fan runs directly off the pump shaft when your engine idles or under light load. As a result, motors can run at a lower RPM. It reduces fuel consumption.

Disadvantages of Thermal Fan Clutches

Like everything in the world, these clutches have some opposing sides, too.

Higher Initial Cost

You usually need to spend more than non-thermal counterparts to use thermal fan clutches. The reason is these clutches have advanced technology and materials. So, it refers to a higher initial investment for vehicle owners – like you and me.

More Maintenance

For sure, thermal clutches have a longer life than other clutches. However, their complex design and materials need more frequent care and replacements. So, again, you need to count more bucks for using these clutches.

Disadvantages of Non-Thermal Fan Clutches

Non-thermal fan clutches also have some disadvantages despite their benefits.

Higher Fuel Consumption

Non-thermal clutches are less efficient than thermal ones. As a result, they cause more significant power loss. Even they may consume fuel slightly higher.

Overheating Issue

Suppose you fail to install or maintain non-thermal fan clutches. Then, the engine may not cool well. It will harm the engine, cause damage, and increase maintenance costs.

The Selection Process: Thermal Fan Clutch vs. Non-Thermal

Both fan clutches have positive and negative effects. Then, you may think, “How do you choose between a thermal and non-thermal fan clutch?” But do not worry, I am making this task easier. You just need to consider a few factors.

Vehicle Type and Usage

Do you drive a high-performance car? Or do you often go in hot climates? Then, I suggest you pick a thermal fan clutch. It is suitable for adjusting its operation based on the engine’s temperature.

If you use your car for daily commuting and fuel efficiency is a priority, select a non-thermal clutch. It reduces overall cost but offers a consistent flow of cooling air.


For saving money, non-thermal clutches are a better choice. But you can reconsider the cost if you think of the superb performance of a thermal clutch.

Let me give you an example: the price of a thermal clutch starts from $39 at SummitRacing. But at the same time, in the same store, non-thermal ones cost around $20-$39 (source).

Maintenance and Replacement Costs

Thermal clutch can last longer than non-thermal counterparts. But it requires more frequent maintenance. But if you are busy with other work like most car owners, start using the non-thermal fan clutch. It does not cost your precious time for regular maintenance.

Final Words

How was the explanation – easy or tough? From my perspective, I have explained things very simply. Well, both fan clutches (thermal and non-thermal) optimize the cooling process. Also, they improve the performance of any engine. Yet, there are some differences that I have mentioned in this blog.

In short, thermal clutches work depending on the temperature of the engine. But, non-thermal ones do not have any thermostatic valve that could work with the temperature.

From an energy and fuel efficiency point of view, you can consider the first one as the winner. But non-thermal will work better if you think of less maintenance and initial cost.

Now, it depends on you! If you drive in hot weather primarily, choose a thermal fan clutch. But for regular driving, I suggest you rethink it, as non-thermal ones are saving you money and time.

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