how to replace ac unit contactor


How to Replace AC Unit Contactor


Having an efficient and functional air conditioning unit is essential, especially during the scorching summer months. The contactor is a crucial component of your AC unit that allows electricity to flow to the compressor and fan motor. Over time, the contactor can become worn out or damaged, leading to issues such as the AC unit not turning on or not cooling properly. In this article, we will guide you through the process of replacing an AC unit contactor, ensuring that your cooling system operates smoothly once again.

Understanding the Role of an AC Unit Contactor

The contactor in an AC unit is responsible for controlling the flow of electrical current to different parts of the cooling system, particularly the compressor and fan motor. It acts as a switch, allowing the unit to turn on and off as needed to regulate the temperature in your home. When the thermostat signals the need for cooling, the contactor closes to send power to the compressor and fan motor, and when the desired temperature is reached, it opens, cutting off the power supply. Over time, the contactor may wear out due to constant use or experience damage that prevents it from functioning correctly.

Identifying the Signs of a Faulty Contactor

Before replacing your AC unit's contactor, it's important to diagnose whether it is indeed the root cause of your cooling system issues. Here are some common signs that indicate a faulty contactor:

1. AC Unit Not Turning On: A malfunctioning contactor can prevent your AC unit from starting, leaving you without cool air during hot summer days. If you notice that the unit is not responding to the thermostat settings, it's worth examining the contactor.

2. Noise and Vibration: A worn-out contactor can make strange noises or cause vibrations when the AC unit is running. These unusual sounds and movements are a clear indication that something is wrong and might require a contactor replacement.

3. Excessive Heating: When a contactor starts to fail, it can lead to overheating of the compressor or other electrical components. If you notice unusual warm temperatures around your AC unit or notice a burning smell, it's crucial to investigate the contactor as a potential issue.

4. Intermittent Operation: A faulty contactor may cause your AC unit to operate inconsistently, turning on and off without any apparent reason. This irregular operation can result in insufficient cooling or increased energy consumption.

Gathering the Required Tools and Supplies

Before embarking on the process of replacing your AC unit's contactor, gather the necessary tools and supplies to ensure a smooth and efficient replacement. Here's a list of items you'll need:

1. Safety Equipment: Safety should always be a priority when working with electricity. Make sure you have gloves, safety glasses, and other protective gear.

2. Replacement Contactor: Purchase a new contactor that matches the specifications of your AC unit. Take note of the voltage and amperage rating of the old contactor to ensure compatibility.

3. Multimeter: A multimeter is essential for checking the voltage and continuity of electrical connections. It will help you identify if the contactor is indeed faulty.

4. Screwdriver: You'll likely need a flathead or Phillips screwdriver to remove screws and access the contactor. Have a set of different sizes available to accommodate various screw types.

5. Wire Strippers: To safely disconnect and reconnect wires, have a reliable pair of wire strippers on hand. They will help to remove the insulation from the wires without causing any damage.

Step-by-Step Guide: Replacing the AC Unit Contactor

Now that you're equipped with the necessary tools and supplies let's dive into the process of replacing your AC unit's contactor. Follow these steps carefully to ensure a successful replacement:

Step 1: Turn Off the Power

Before beginning any work on your AC unit, it's crucial to turn off the power supply. Locate the circuit breaker or the disconnect box near the unit and switch it off. This step will prevent any accidents or electrical shocks while working.

Step 2: Remove the Access Panel

Using the appropriate screwdriver, carefully remove the screws securing the access panel of your AC unit. Set the screws aside in a safe place to avoid misplacing them.

Step 3: Locate the Contactor

Once the access panel is removed, locate the contactor. It is a small, rectangular-shaped device usually mounted near the compressor. Take a moment to observe how the wires are connected, or capture a photograph to guide you during reinstallation.

Step 4: Disconnect Wires

Using the wire strippers, gently remove the insulation from the wires connected to the contactor. Take note of the wire colors and their respective locations for easy reconnection later.

Step 5: Remove the Old Contactor

With the wires detached, carefully unscrew the contactor from the mounting bracket. Take a moment to examine the contactor and note its position and orientation.

Step 6: Install the New Contactor

Place the new contactor in the same position and orientation as the old one. Secure it in place by reinserting and tightening the screws.

Step 7: Reconnect Wires

Using your photograph or reference notes, reconnect the wires to the new contactor. Ensure a proper and secure connection without leaving any loose ends.

Step 8: Turn On the Power

After ensuring that all connections are secure, switch the power supply back on. Test the AC unit by setting the thermostat to the desired temperature and waiting for the unit to kick in. Check if the contactor is functioning correctly by observing it during operation.

Safety Precautions

While replacing an AC unit contactor can be a feasible task, it's essential to keep safety precautions in mind throughout the process:

1. Power Off: Always turn off the power supply to your AC unit before starting any work. This will prevent any electrical shocks or accidents.

2. Capacitors: Capacitors store electrical energy, even when the unit is turned off. Before touching any components, discharge the stored energy by using an insulated screwdriver or following the manufacturer's instructions.

3. Professional Assistance: If you're unsure about any step or feel uncomfortable working with electrical components, it's best to seek professional assistance. HVAC technicians have the expertise and experience necessary to handle such tasks safely.


Replacing an AC unit contactor can restore the functionality and efficiency of your cooling system, allowing you to enjoy a comfortable home during hot summer days. By following the step-by-step guide and taking necessary safety precautions, you can successfully replace the faulty contactor and restore your AC unit's performance. Remember always to consult the manufacturer's instructions or seek professional assistance if you encounter any difficulties or uncertainties along the way. Stay cool!


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