how does a ac contactor work



An AC contactor is an essential component in an air conditioning system that plays a crucial role in controlling the flow of electrical current. It allows the system to switch on and off, ensuring efficient operation and temperature regulation. Understanding how an AC contactor works is fundamental for both homeowners and technicians to troubleshoot any issues and ensure optimal performance. In this article, we will explore the inner workings of an AC contactor, its components, and the functions it performs within an air conditioning system.

Overview of an AC Contactor

An AC contactor, also known as a relay, is an electrical switch device designed to control the flow of electricity to the compressor and condenser fan in an air conditioning system. When the thermostat signals a cooling demand, the contactor engages the compressor and the condenser fan, allowing them to operate. Conversely, when the desired temperature is reached or the system is turned off, the contactor disengages, cutting off the power supply to these components.

Components of an AC Contactor

AC contactors comprise several key components that work in synchronization to facilitate the switching process. Understanding these components is vital to comprehending the overall functionality of an AC contactor. Let's delve into each component:

1. Coil:

The coil is an electromagnetic winding that creates a magnetic field when an electric current passes through it. This magnetic field is responsible for attracting the moving parts of the contactor, initiating the electrical contact. The coil typically operates on low voltage, ensuring user safety and efficient performance.

2. Contacts:

Contacts are two metal strips, typically made of silver-based materials, that establish electrical connections when closed. They are positioned in such a way that, when the coil is energized, the magnetic force pulls these contacts together, completing the circuit and allowing current to flow to the compressor and condenser fan. When the coil is de-energized, the contacts separate, interrupting the electrical circuit.

3. Contact Springs:

Contact springs are essential components that provide the necessary force to ensure proper contact closure and contact separation. They help in maintaining the integrity and longevity of the contacts, minimizing the risk of arcing and undesirable electrical fluctuations. Contact springs contribute to the overall reliability and performance of the AC contactor.

4. Frame:

The frame is the outer structure that encapsulates and holds all the internal components. It is constructed from durable materials to withstand environmental factors such as temperature, humidity, and vibrations. The frame also serves as an insulating barrier, preventing contact with the live components and ensuring safety during operation.

5. Arc Chute:

An arc chute is a safety feature incorporated into AC contactors to suppress and extinguish any arcing that occurs when the contacts open or close. Arcing is the result of the electrical current attempting to continue flowing even when the contacts are in transition. The arc chute redirects and dissipates this energy, preventing damage to the contacts and minimizing electrical interference in the system.

The Working Mechanism of an AC Contactor

Understanding the working mechanism of an AC contactor involves comprehending the sequence of events that occur when the system is switched on or off. Let's explore the step-by-step process:

1. System Activation:

When the cooling demand is signaled by the thermostat, an electric current flows through the coil of the AC contactor. This energizes the coil and creates a magnetic field in the vicinity.

2. Magnetic Attraction:

The magnetic field generated by the coil attracts the moving parts of the contactor, causing them to move towards each other. This movement brings the contacts in contact with each other and establishes an electrical connection.

3. Current Flow:

With the contacts securely closed, the electrical circuit is completed, allowing the current to flow to the compressor and condenser fan. These components are powered, enabling them to initiate the cooling process.

4. Temperature Regulation:

As the air conditioning system continues to operate, the thermostat continuously monitors the ambient temperature. Once the desired temperature is achieved, the thermostat signals the system to deactivate, which leads to the next series of events.

5. Disengagement:

Upon receiving the signal to deactivate, the electrical current to the coil is interrupted. This causes the magnetic field to dissipate, subsequently releasing the attraction between the moving parts. As a result, the contacts separate, breaking the electrical connection.

6. Power Cutoff:

With the contacts open, the electrical circuit to the compressor and condenser fan is disconnected, cutting off the power supply to these components. This ensures that the system stops operating, preventing unnecessary energy consumption.


AC contactors are integral components in air conditioning systems, responsible for controlling the flow of electricity to the compressor and condenser fan. Through the interaction of various components like the coil, contacts, contact springs, frame, and arc chute, the contactor enables the system to switch on and off according to the cooling demands. Understanding the working mechanism of an AC contactor empowers homeowners and technicians to diagnose and rectify any potential issues, ensuring efficient operation and extending the lifespan of the air conditioning system.


Just tell us your requirements, we can do more than you can imagine.
Send your inquiry

Send your inquiry

Choose a different language
Current language:English