In-Depth Look at Car Air Conditioning Systems

Daniel Mwangi
12 Min Read
Image of car air conditioning

In-depth Look at Car Air Conditioning Systems

Introduction to Car Air Conditioning

In the sweltering heat of summer or the cold grip of humidity, car air conditioning (AC) systems emerge as a saviour, providing respite and comfort during drives. These systems have evolved significantly over the years, transforming from basic coolers to sophisticated climate control mechanisms. This article provides a comprehensive exploration of the two primary types of car AC systems: the traditional belt-driven compressor system and the modern electric compressor system.

By delving into their inner workings, advantages, drawbacks, common issues, and potential solutions, we gain a profound understanding of how these systems contribute to our driving experiences.

Types of Car AC Systems

Belt-Driven Compressor System

The backbone of traditional AC setups, the belt-driven compressor system, relies on the mechanical power of the engine to operate. The engine’s serpentine belt connects to the compressor, driving its operation. Once engaged, the compressor pressurises the refrigerant, typically a compound like R-134a, initiating a cycle of heat exchange. The high-pressure gas is then directed to the condenser located at the front of the vehicle, where it releases heat and transforms into a high-pressure liquid.

As the liquid refrigerant passes through the expansion valve, it undergoes rapid depressurization, converting into a low-pressure gas and causing it to evaporate and absorb heat. The cold gas is then sent to the evaporator situated in the cabin, where the blower fan circulates air over the chilled coils, resulting in cooled, dehumidified air being propelled into the interior.

Electric Compressor System

A leap forward in technology, the electric compressor system features an electrically driven compressor. This electric motor-driven compressor decouples the AC operation from the engine’s operation, allowing for independent climate control. Just like its belt-driven counterpart, the electric compressor system also relies on the same components—condenser, evaporator, and expansion valve—but introduces electronic controls that provide more precise modulation of cooling output.

How Each System Works

  1. Belt-Driven Compressor System: The engagement of the AC activates the serpentine belt, setting the compressor into motion. The refrigerant’s journey from gas to liquid to gas again drives the heat exchange process, culminating in a refreshing inflow of cool air into the vehicle’s cabin.
  2. Electric Compressor System: Operating independently of the engine’s RPM, the electric compressor system offers heightened control. The electric compressor’s motor drives the refrigerant cycle, enabling accurate regulation of cooling performance. The outcome is similar to that of the belt-driven system, but with the added benefits of reduced engine load and enhanced efficiency.

Pros and Cons of Belt-Driven Compressor System

  1. Pros:
  • A proven and time-tested technology with a history of reliability.
  • Effective cooling performance, particularly at higher engine RPMs and speeds.
  • Generally more economical in terms of repair and maintenance costs.

2. Cons:

  • Imposes additional load on the engine, potentially leading to decreased fuel efficiency.
  • Limited control over AC operation due to its direct connection to engine speed.
  • Requires periodic maintenance of belts and associated components.

Pros and Cons of Electric Compressor System

  1. Pros:
  • Independent operation reduces strain on the engine, potentially resulting in improved fuel efficiency.
  • Enhanced control over AC performance, offering precise temperature regulation.
  • Reduced vibrations and noise in comparison to belt-driven systems.

2. Cons:

  • Initial system installation costs are typically higher due to the inclusion of an electric compressor and advanced electronic controls.
  • Repairs and maintenance may demand specialised expertise and components.

Common Car AC Issues and Solutions

  1. Insufficient Cooling:
  • Issue: Inadequate airflow or air that’s not as cold as expected.
  • Solution: Evaluate and adjust refrigerant levels, inspect compressor functionality, and assess cabin air filters. If necessary, recharge the refrigerant.

2. Strange Odours:

  • Issue: Unpleasant odours emanating from the AC system.
  • Solution: Clean or replace cabin air filters, conduct thorough cleaning of evaporator coils, and apply antibacterial treatments to eliminate odours.

3. Refrigerant Leakage:

  • Issue: Loss of refrigerant leading to compromised cooling effectiveness.
  • Solution: Identify and rectify leaks, followed by replenishing the system’s refrigerant levels.

4. Compressor Failure:

  • Issue: Compressor not engaging or emitting unusual noises during operation.
  • Solution: Swap out the malfunctioning compressor and ensure proper lubrication and refrigerant levels in the system.

Wrap-up on Car AC Systems

The realm of car air conditioning systems has witnessed a transformative evolution, with the belt-driven and electric compressor systems representing two distinct chapters. Each system offers its own set of advantages and limitations, appealing to different priorities and preferences.

Regular maintenance and swift resolution of issues are pivotal to guaranteeing a comfortable and refreshing driving experience, regardless of the chosen AC system. As technology continues to advance, the ongoing refinement of car AC systems promises even greater efficiency, control, and comfort for drivers and passengers alike.

Components Within Car Air Conditioning Systems

The terms “expansion valve system” and “fixed orifice tube system” refer to different components within car air conditioning systems, not different types of AC systems themselves. Let me clarify:

Expansion Valve System

The expansion valve is a component within the air conditioning system that plays a critical role in regulating the flow of refrigerant. It is commonly used in both belt-driven compressor systems and electric compressor systems. The expansion valve is responsible for controlling the release of high-pressure liquid refrigerant into the low-pressure side of the system, where it rapidly expands and evaporates, absorbing heat from the surrounding air. This process cools the air before it enters the cabin. The expansion valve system is a part of both AC system types and helps manage the refrigerant’s phase change.

Fixed Orifice Tube System

The fixed orifice tube (also known as an orifice tube) is another component used in car air conditioning systems. Like the expansion valve, it is used in both belt-driven compressor systems and electric compressor systems. The orifice tube is positioned between the condenser and the evaporator and serves as a restriction point. It causes a drop in pressure, allowing the refrigerant to expand and evaporate, cooling the air.

The key difference between the expansion valve and the fixed orifice tube is that the expansion valve offers more precise control over the refrigerant flow, while the orifice tube provides a fixed restriction without the fine-tuning capabilities.

In summary, the terms “expansion valve system” and “fixed orifice tube system” refer to components within the broader context of car air conditioning systems, and both types of AC systems (belt-driven compressor and electric compressor) can incorporate either an expansion valve or a fixed orifice tube to control the refrigerant flow and achieve cooling.

How Expansion Valve Works

The expansion valve is a crucial component in car air conditioning systems that regulate the flow of refrigerant. It’s usually located between the condenser and the evaporator. The valve operates based on the pressure and temperature of the refrigerant. As high-pressure, high-temperature liquid refrigerant exits the condenser, it enters the expansion valve. The valve’s internal mechanism controls the opening and closing of a small orifice or passage.

When the liquid refrigerant passes through this orifice, it experiences a sudden drop in pressure, causing it to expand and evaporate rapidly. This phase change from liquid to gas results in a significant cooling effect, allowing the refrigerant to absorb heat from the surrounding air. The cooled refrigerant gas is then directed into the evaporator, where it cools the air before it’s blown into the vehicle’s cabin.

Differences in Operation: The expansion valve offers precise control over the flow of refrigerant based on pressure and temperature conditions. This control allows for optimal cooling performance, especially during varying conditions such as idling and highway driving. Expansion valves can adjust refrigerant flow rates dynamically, responding to changes in cooling demands.

Similarities: Both belt-driven compressor systems and electric compressor systems can incorporate expansion valves. The fundamental principle of cooling through phase change remains the same in both cases.


  • Precise Control: The expansion valve provides fine-tuned control over refrigerant flow, ensuring efficient cooling across different driving scenarios.
  • Better Efficiency: By regulating the amount of refrigerant entering the evaporator, the expansion valve contributes to improved energy efficiency.

How Fixed Orifice Tube Works

The fixed orifice tube, also positioned between the condenser and the evaporator, functions as a fixed restriction point for the refrigerant flow. Unlike the expansion valve, which modulates the flow, the orifice tube provides a constant restriction. As the high-pressure liquid refrigerant passes through the orifice tube, it rapidly expands due to the sudden drop in pressure, leading to evaporative cooling. The cooled refrigerant gas then enters the evaporator to cool the air.

Differences in Operation: Unlike the expansion valve, which can adjust refrigerant flow based on conditions, the fixed orifice tube provides a consistent restriction level. This lack of adjustment means that the cooling performance may not be as optimised across all driving scenarios.

Similarities: Similar to the expansion valve, the fixed orifice tube can be used in both belt-driven compressor systems and electric compressor systems.


  • Simplicity: The fixed orifice tube has fewer moving parts compared to the expansion valve, leading to potentially lower maintenance requirements and reduced chances of failure.
  • Lower Cost: Due to its simple design, the fixed orifice tube is generally less expensive to manufacture and replace.

Quick Walk-Through on Components

Both the expansion valve and the fixed orifice tube are essential components in car air conditioning systems that contribute to the cooling process by facilitating the phase change of refrigerant. The expansion valve provides fine control over refrigerant flow, enabling more precise cooling performance. On the other hand, the fixed orifice tube offers simplicity and potentially lower costs.

The choice between these components often depends on factors like the desired level of cooling control, system complexity, and cost considerations. Regardless of the component used, both play a critical role in creating a comfortable and refreshing driving environment.

Share this Article
Leave a comment