how to replace an ac contactor



Replacing an AC contactor may seem like a daunting task, but with the right knowledge and tools, it can be a relatively simple process. The AC contactor plays a vital role in the functioning of your air conditioning unit, making it crucial to ensure it is in good working condition. Over time, contactors can wear out or become faulty, leading to issues in your AC system. In this article, we will guide you through the process of replacing an AC contactor, step-by-step, to help you restore the proper functioning of your air conditioning unit.

What is an AC Contactor?

Before diving into the replacement process, it is essential to understand the significance of an AC contactor. An AC contactor is an electrical switch that controls the flow of electricity to the compressor and the condenser fan motor in an air conditioning unit. When the thermostat signals for cooling, the contactor engages, allowing the flow of electricity to power these components. Over time, due to wear and tear or electrical issues, the contactor may fail, leading to problems with the air conditioner's performance. Replacing the faulty contactor can resolve these issues and restore the unit's functionality.

Tools and Safety Precautions

Before starting the replacement process, it is crucial to gather the necessary tools and take safety precautions to avoid any electrical hazards. Here are some tools you will need:

- Screwdriver (flathead and Phillips)

- Needle-nose pliers

- Voltage tester

- Replacement AC contactor (compatible with your air conditioning unit)

Additionally, ensure your safety by taking the following precautions:

1. Turn off the power: To prevent any electrical accidents, turn off the power supply to your air conditioning unit. Locate the electrical panel and switch off the circuit breaker that controls the AC unit.

2. Use protective gear: Wear safety gloves and goggles to protect yourself from any potential hazards, such as electrical shocks or debris.

3. Double-check the power supply: Use a voltage tester to ensure that there is no electrical current flowing through the system before proceeding with the replacement.

Now that we have covered the basic introduction, let us delve into the step-by-step process of replacing an AC contactor.

Identifying the Contactor

The first step in replacing an AC contactor is to identify its location within the air conditioning unit. Typically, the contactor is found inside the electrical panel of the outdoor condenser unit. It is a rectangular-shaped box with wires connected to it. To locate the contactor, follow these steps:

1. Turn off the power supply to the AC unit from the electrical panel.

2. Open the access panel of the outdoor condenser unit. This panel is usually secured with screws or latches.

3. Once the panel is open, visually inspect the components to locate the contactor. The contactor is recognizable as a black box with numerous wires attached to it.

Removing the Old Contactor

After identifying the contactor, the next step is to remove the old and faulty contactor from the electrical panel. Follow these steps carefully:

1. Ensure the power supply to your air conditioning unit is turned off.

2. Take a picture or make a note of the wiring connections to ensure proper reinstallation of the new contactor. This step is crucial to avoid any confusion while reconnecting the wires later.

3. Using a screwdriver, carefully remove the screws securing the contactor to the electrical panel. Take note of the screw positions, as they may vary depending on the unit.

4. Once the screws are removed, gently pull out the contactor, taking care not to damage any wires connected to it.

5. Using needle-nose pliers, carefully disconnect the wires attached to the contactor. Note that different contactors may have varying numbers of wire connections, so ensure you remove all of them.

With the old contactor successfully removed, we can move on to the exciting part - installing the new AC contactor.

Installing the New Contactor

When installing the new contactor, it is essential to ensure it is compatible with your air conditioning unit. Consult the manufacturer's guidelines or seek professional advice if you are unsure about the compatibility. Let's proceed with the installation process step-by-step:

1. Take the new contactor and carefully attach the wires to their respective terminals. Refer to the picture or notes you took while removing the old contactor to ensure correct connections. It is essential to connect each wire to the corresponding terminal to avoid any electrical malfunctions.

2. Once all the wires are securely connected, place the contactor back into the electrical panel in the same position as the old one.

3. Using a screwdriver, insert the screws in their respective holes and tighten them to secure the new contactor in place. Ensure the contactor is snug and properly aligned within the panel.

4. With the contactor securely installed, double-check the wiring connections to ensure they are properly seated and there are no loose connections.

With the new contactor successfully installed, we are now ready to test the unit and restore its functionality.

Testing the AC Unit

Before powering up the AC unit, it is crucial to perform a thorough test to ensure the replacement contactor is functioning correctly. Follow these steps to test the unit:

1. Turn on the power supply to the air conditioning unit from the electrical panel.

2. Switch on the thermostat and set it to the desired cooling temperature.

3. Step outside and listen for any unusual sounds coming from the outdoor condenser unit. A correctly functioning contactor should engage, and you should hear a distinct click sound when the compressor and condenser fan motor start.

4. Visually inspect the contactor to ensure it is holding up well under the load. If the contactor appears to be vibrating excessively or making any unusual noises, there may be an issue with the installation or the contactor itself.

If the AC unit is working correctly and the contactor functions as expected, congratulations on successfully replacing the AC contactor! However, if you encounter any issues during the testing phase, it is advisable to consult a professional technician to diagnose and resolve the problem.


Replacing an AC contactor is a task that can be accomplished with a little knowledge and the right tools. By following the step-by-step process outlined in this article, you can replace a faulty contactor in your air conditioning unit and restore its proper functioning. Remember to gather the necessary tools, take safety precautions, and consult professional advice if needed. By ensuring the compatibility of the new contactor and carefully reconnecting the wires, you can successfully replace the contactor and enjoy the benefits of a fully functional AC unit. So, don't let a faulty contactor keep you from enjoying cool air on hot summer days; take the plunge and replace it to bring comfort back into your home.


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