how much is a contactor for ac unit


What is a Contactor for AC Unit and How Much Does It Cost?


When it comes to air conditioning units, one of the crucial components that plays a significant role in their overall functioning is the contactor. A contactor is an electrically controlled switch that allows the flow of electricity to the compressor and the condenser fan motor in an AC unit. It acts as the central hub, allowing the system to start, stop, and regulate the flow of power. However, like any other essential component, a contactor can wear out or become faulty over time, which may require a replacement. In this article, we will explore all aspects of a contactor for AC units, including its functions, signs of a faulty contactor, and most importantly, the cost associated with purchasing and installing a new one.

Understanding the Functions of a Contactor in an AC Unit

A contactor functions as a control switch, enabling the flow of electricity from the main circuit to the compressor and the condenser fan motor. It consists of a coil that, when energized, generates a magnetic field, attracting the contacts and allowing the power to flow. When the contacts are closed, the AC unit receives power, and the compressor and condenser fan motor start running. On the other hand, when the contacts are open, the power flow is cut off, shutting down the unit. This simple yet essential function ensures the smooth operation of an air conditioning system.

A contactor comprises several key components, including the energizing coil, contacts, and terminals. The energizing coil is responsible for generating the magnetic field that attracts or repels the contacts, allowing or preventing the flow of electricity. The contacts, made from high-quality conductive materials, ensure a reliable and secure connection. Lastly, the terminals serve as the connection points for the main circuit and the control circuit.

Signs of a Faulty Contactor in an AC Unit

Over time, a contactor may develop wear and tear due to frequent use, exposure to environmental conditions, or electrical issues. It is crucial to identify the signs of a faulty contactor to prevent further damage to the AC unit and ensure optimal performance. Here are some common signs that indicate a faulty contactor:

1. Frequent System Tripping: If your AC unit frequently trips the circuit breaker or blows a fuse, it could be due to a faulty contactor. A worn-out contactor may cause electrical arcing or short circuits, leading to increased power draw and subsequent tripping.

2. Inconsistent Cooling: Noticeable fluctuations in temperature or inconsistent cooling throughout your space can be a result of a faulty contactor. When the contactor does not engage or disengage properly, the compressor and fan motor may not receive the required power, impacting efficiency.

3. Loud Clicking Noises: Unusual clicking or buzzing sounds coming from your AC unit can indicate an issue with the contactor. When the contactor is worn out or damaged, it may produce these audible indications of malfunctioning.

4. Stuck Contacts: If the contacts of the contactor become stuck or welded together, the AC unit may continuously run without any control. This can lead to excessive cooling, increased energy consumption, and potential damage to the components.

5. Burn Marks or Signs of Melting: Inspect the contactor for any burn marks, signs of melting, or discolored areas. These could be indicators of excessive heat buildup, sparking, or electrical arcing, which can result from a faulty contactor.

The Cost of a Contactor for AC Unit

Now that we have a good understanding of the vital role a contactor plays in an AC unit, let's delve into the cost associated with purchasing and installing a new contactor. The cost of a contactor can vary depending on various factors such as the brand, quality, compatibility, and where you buy it from. On average, a contactor for an AC unit can cost anywhere between $20 to $150.

The price range primarily depends on the type and quality of the contactor. Single-pole contactors, which are commonly used in smaller residential AC units, are usually more affordable compared to double-pole or three-pole contactors used in larger commercial systems. Additionally, contactors that can handle higher amperages and voltages tend to be more expensive due to their enhanced capacity and durability.

When purchasing a contactor, it is essential to consider its compatibility with your specific AC unit model. It is highly recommended to consult the manufacturer's guidelines or seek professional advice to ensure you select the correct contactor that fits your unit's electrical specifications and requirements.

Professional Installation vs. DIY

The installation of a contactor in an AC unit involves electrical connections and requires a certain level of expertise. While some experienced individuals may consider DIY installation, it is generally recommended to hire a licensed HVAC technician for this task. Professional installation ensures proper wiring, connection, and overall safety of the system, reducing the risk of electrical hazards or further damage to the unit.

The cost of professional installation ranges from $100 to $300, depending on various factors such as the complexity of the installation, location, and contractor rates. Investing in professional installation not only guarantees a correct and safe installation but also saves you time and effort in understanding the intricacies of the electrical system.

In some cases, the cost of purchasing a new contactor may include professional installation services offered by the seller or manufacturer. It is worth inquiring about such options when making a purchase to potentially save on installation costs.


In conclusion, a contactor is a vital component in an AC unit that controls the flow of electricity to the compressor and condenser fan motor. It allows the system to start, stop, and regulate power flow, thereby ensuring optimal cooling and performance. Signs of a faulty contactor include frequent system tripping, inconsistent cooling, unusual noises, stuck contacts, and burn marks. The cost of a contactor can vary between $20 to $150, depending on the type and quality. It is essential to consider compatibility with your AC unit and seek professional installation for a safe and proper installation. By understanding the importance and cost associated with a contactor, you can maintain the efficiency and longevity of your AC unit, keeping your space cool and comfortable during hot summer days.


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