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Car Cooling System or A/C System? Where Does Your Problem Lie?


Feet hanging out of a hot car

As summer hits, keeping your and your car cool are essential, especially in the southern Illinois heat. Two critical systems that perform this task, but are often cause confused with each other, are the cooling system and the air conditioning (A/C) system. While both systems are vital for maintaining comfort and performance, they serve very different purposes. As your automotive experts, PMR Automotive is here to help break down the systems and explain.



What is a Car Cooling System?


Car overheating from bad cooling system

The primary purpose of a car's cooling system is to maintain the engine at an optimal temperature. Internal combustion engines generate a significant amount of heat during operation. Without a cooling system, the engine would overheat, leading to severe damage or complete engine failure. The cooling system helps to dissipate this excess heat, ensuring the engine operates efficiently and reliably. The cooling system is also essential year round, no matter the outside temperature.


Key Components of the Cooling System

  1. Radiator: The radiator is the central component of the cooling system. It transfers heat from the coolant to the outside air. As hot coolant passes through the radiator, it is cooled by air flowing over the radiator's fins.

  2. Water Pump: The water pump circulates the coolant through the engine, radiator, and other components. It ensures a continuous flow of coolant, preventing overheating.

  3. Thermostat: The thermostat regulates the flow of coolant based on the engine's temperature. When the engine is cold, the thermostat remains closed, allowing the engine to warm up quickly. Once the engine reaches its optimal temperature, the thermostat opens, allowing coolant to flow and maintain a stable temperature.

  4. Coolant: Also known as antifreeze, coolant is a fluid that absorbs heat from the engine and transfers it to the radiator. It also prevents the engine from freezing in cold temperatures.

  5. Cooling Fans: These fans enhance the airflow over the radiator, especially when the vehicle is stationary or moving slowly. They help dissipate heat more effectively.

  6. Hoses and Belts: Hoses transport coolant between the engine, radiator, and other components, while belts drive the water pump and other auxiliary components.


How the Cooling System Works

The cooling process begins when the engine starts. As the engine heats up, the thermostat remains closed, allowing the engine to reach its optimal operating temperature quickly. Once the desired temperature is achieved, the thermostat opens, and the water pump circulates coolant through the engine and radiator. The coolant absorbs heat from the engine and releases it into the air through the radiator. This cycle continues, ensuring the engine stays within a safe temperature range.



What is a Car Air Conditioning (A/C) System?


Car a/c system controls

In contrast to the cooling system, the primary purpose of the air conditioning (A/C) system is to provide comfort to the vehicle's occupants by cooling the cabin air. The A/C system reduces the temperature inside the car, removes humidity, and filters the air, creating a pleasant environment during hot weather. Even in the winter, the A/C system is put to use, helping your defroster keep your windshield from fogging and even freezing.


Key Components of the A/C System

  1. Compressor: The compressor is the heart of the A/C system. It pressurizes the refrigerant, converting it from a low-pressure gas to a high-pressure gas. This process raises the refrigerant's temperature.

  2. Condenser: The condenser acts as a heat exchanger, cooling the high-pressure refrigerant gas and converting it into a high-pressure liquid. It is typically located in front of the radiator.

  3. Evaporator: Located inside the cabin, the evaporator absorbs heat from the air, cooling it down. As the refrigerant passes through the evaporator, it changes from a liquid to a low-pressure gas, absorbing heat in the process.

  4. Expansion Valve or Orifice Tube: This component regulates the flow of refrigerant into the evaporator, allowing the refrigerant to expand and cool before it enters the evaporator.

  5. Refrigerant: The refrigerant is a specialized fluid that circulates through the A/C system, absorbing and releasing heat to cool the cabin air.

  6. Receiver-Drier or Accumulator: This component removes moisture and contaminants from the refrigerant, ensuring the system operates efficiently and preventing damage to other components.


How the A/C System Works

The A/C process begins when the vehicle's A/C system is activated. The compressor pressurizes the refrigerant, transforming it into a high-pressure gas. This gas then flows to the condenser, where it releases heat and changes into a high-pressure liquid. The liquid refrigerant travels to the expansion valve or orifice tube, where it expands and cools before entering the evaporator. Inside the evaporator, the refrigerant absorbs heat from the cabin air, cooling it down. The cooled air is then blown into the cabin, while the refrigerant, now a low-pressure gas, returns to the compressor to begin the cycle anew.



Comparing the Cooling System and A/C System

Different Objectives

While both systems involve temperature regulation, their objectives are fundamentally different. The cooling system is essential for maintaining the engine's operating temperature, preventing overheating and ensuring optimal performance. In contrast, the A/C system is designed to enhance passenger comfort by cooling and dehumidifying the cabin air.


Distinct Components and Processes

The components and processes of each system are tailored to their specific functions. The cooling system relies on coolant, a thermostat, and a radiator to manage engine temperature. The A/C system, on the other hand, uses refrigerant, a compressor, and an evaporator to cool the cabin air. These systems operate independently but can influence each other indirectly.


Interaction and Impact on Each Other

Although the cooling and A/C systems operate separately, they can impact each other. For example, the A/C system adds a load to the engine when in use, potentially increasing engine temperature. This increased load requires the cooling system to work harder to maintain optimal engine temperature. Often times, in many newer vehicles, if your vehicle is overheating, the car will automatically shut off the A/C to avoid the heavy load. Additionally, the condenser of the A/C system is typically located in front of the radiator, meaning heat from the condenser can affect the radiator's ability to dissipate heat efficiently.


Maintenance and Common Issues

Cooling System Maintenance

  1. Regular Coolant Checks: Ensure the coolant level is adequate and top it up if necessary. Check for coolant leaks and address them promptly. If done regularly, coolant flushes and drain and fills can help to maintain adequate coolant conditions.

  2. Thermostat Inspection: A faulty thermostat can lead to engine overheating or underheating. Replace it if it shows signs of malfunction.

  3. Radiator Maintenance: Keep the radiator clean and free of debris. Check for leaks and ensure the radiator cap is in good condition.

  4. Water Pump and Hoses: Inspect the water pump and hoses for wear and tear. Replace any damaged or leaking components.

Common Cooling System Issues

  • Overheating: Caused by low coolant levels, a faulty thermostat, or a malfunctioning water pump.

  • Coolant Leaks: Often occur due to worn hoses, a damaged radiator, or a faulty water pump.

  • Thermostat Failure: Can result in the engine not reaching its optimal temperature or overheating.


A/C System Maintenance

  1. Regular Refrigerant Checks: Ensure the refrigerant level is sufficient and recharge it if necessary. Check for leaks in the system.

  2. Compressor Inspection: A malfunctioning compressor can impact the entire A/C system. Listen for unusual noises and replace the compressor if needed.

  3. Condenser and Evaporator Cleaning: Keep these components clean and free of debris to maintain efficient operation.

  4. Filter Replacement: Replace the cabin air filter regularly to ensure clean air circulation.

Common A/C System Issues

  • Insufficient Cooling: Often caused by low refrigerant levels, a faulty compressor, or a clogged evaporator.

  • Refrigerant Leaks: Can occur due to damaged hoses, seals, or connections.

  • Compressor Failure: May result from electrical issues, inadequate lubrication, or wear and tear.



Understanding the difference between a car's cooling system and its A/C system is crucial for maintaining your vehicle's performance and comfort. The cooling system is essential for managing engine temperature, preventing overheating, and ensuring the engine runs efficiently. In contrast, the A/C system focuses on enhancing passenger comfort by cooling and dehumidifying the cabin air.


Regular maintenance of both systems is vital to avoid common issues and ensure your vehicle operates smoothly. By keeping an eye on coolant levels, refrigerant levels, and the condition of key components, you can prevent problems before they arise and enjoy a comfortable and reliable driving experience.


In summary, while the cooling system and A/C system may seem similar at first glance, they serve distinct and vital roles in your vehicle. Understanding their differences and how they interact can help you maintain your car more effectively and appreciate the technology that keeps you comfortable on the road.


If you ever had questions or need service for your cooling system or the A/C, don't hesitate to call the experts at PMR Automotive. They are versed in all makes and models and can service both the old and new A/C systems in vehicles.

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