how to replace contactor on ac unit


How to Replace Contactor on AC Unit

Is your air conditioning unit not functioning properly? One common issue that may arise is a faulty contactor. The contactor in your AC unit is responsible for controlling the flow of electricity to the compressor and the condenser fan motor. Over time, this component can wear out or become damaged, leading to a variety of cooling problems. Fortunately, replacing the contactor is a relatively simple task that you can do yourself, saving you time and money. In this article, we will guide you through the step-by-step process of replacing the contactor on your AC unit.

The Importance of the Contactor

Before we delve into the steps of replacing the contactor, let's first understand the importance of this component. The contactor plays a crucial role in the operation of your air conditioning system. When the temperature in your home rises above the set-point on your thermostat, the contactor receives a signal from the thermostat to close the circuit and start the compressor and the condenser fan motor. This, in turn, enables the cooling process to begin.

A faulty contactor can cause a range of issues with your air conditioning system. It may prevent the compressor from starting, resulting in warm air blowing from the vents. Additionally, a malfunctioning contactor can cause the system to cycle on and off frequently, leading to excessive energy consumption and reduced overall efficiency. Identifying and replacing a faulty contactor as soon as possible is essential for maintaining optimal cooling performance and preventing further damage to your AC unit.

Gather the Necessary Tools

Before you begin, gather the tools and equipment you will need to replace the contactor on your AC unit. Here's a list of the items you'll require:

1. Screwdriver set (flathead and Phillips head)

2. Needle-nose pliers

3. Insulated gloves

4. Electrical tester (for safety)

5. Replacement contactor (make sure to match the specifications of your existing contactor)

6. Wire nuts and electrical tape (for securing the wires)

These tools are readily available at most hardware stores and will ensure that you have everything you need to successfully complete the contactor replacement.

1. Turn off the Power

Safety should always be your top priority when working with electrical components. Begin by turning off the power to your AC unit. This can typically be done by shutting off the corresponding circuit breaker at your main electrical panel. Double-check that the unit is completely disconnected from its power source before proceeding.

To be absolutely certain that the power is off, you can use an electrical tester to check for voltage. Follow the manufacturer's instructions for the specific tester you have. Always prioritize safety and take the necessary precautions when working with electricity.

2. Access the Contactor

Once you've ensured that the power is turned off, locate the contactor on your AC unit. The contactor is typically found in the outdoor unit and is enclosed in a metal box. Remove the screws securing the cover of the unit and carefully lift it off to expose the contactor inside.

3. Tag and Disconnect the Wires

Before removing the wires from the contactor, it is crucial to label them. This step will make it easier for you to reconnect the wires correctly when installing the new contactor. Take your time to identify each wire and mark it accordingly using masking tape or any other labeling method that works for you.

Once you've labeled the wires, use needle-nose pliers to disconnect them from the terminals of the contactor. Gently pull the wires free, taking care not to damage them. If any wires are damaged or frayed, it's best to replace them before proceeding further.

4. Remove the Old Contactor

With the wires disconnected, you can now remove the old contactor from your AC unit. Take note of how the contactor is secured in place, as the method may vary depending on the make and model of your unit. In most cases, you will need to unscrew the contactor from the mounting bracket.

Once the screws are removed, carefully pull the contactor away from the mounting bracket and set it aside. Be mindful of any additional components or wires that may be attached to the contactor as you remove it. Take note of their arrangement to ensure proper installation of the new contactor.

5. Install the New Contactor

Now that you've removed the old contactor, it's time to install the new one. Begin by positioning the new contactor in the same orientation as the old one. Align the screw holes of the contactor with the mounting bracket and secure it in place using the screws you previously removed.

Ensure that the contacts of the contactor align with the corresponding terminals, as this will determine the flow of electricity. If there were any additional components or wires connected to the old contactor, attach them to the new contactor as well, following the arrangement you noted earlier.

6. Reconnect the Wires

Next, you will need to reconnect the wires to the new contactor. Refer to the labels you made earlier and attach each wire to the appropriate terminal on the contactor. Make sure the connections are secure but avoid overtightening, as this may damage the wires or terminals.

After reconnecting all the wires, double-check your work to ensure that all connections are correct and secure. Loose or improper connections can lead to further electrical problems and may even pose a safety hazard.

7. Replace the Cover and Restore Power

With the new contactor installed and all the wires securely connected, it's time to restore power to your AC unit. Replace the cover of the unit and screw it back into place. Ensure that the cover is properly aligned and fits securely to protect the internal components.

Double-check that the power is off at the main electrical panel and then switch on the circuit breaker corresponding to your AC unit. This will restore power to the unit and allow you to test the functionality of the newly installed contactor.


Replacing the contactor on your AC unit is a manageable task that can be completed with basic tools and some careful attention to detail. By following the steps outlined in this guide, you can restore the proper functioning of your air conditioning system and save money by avoiding professional service charges.

Remember to prioritize safety throughout the process, always turning off the power and taking precautions when working with electrical components. Additionally, label and reconnect the wires correctly to ensure a successful installation.

If you are unsure or uncomfortable performing the replacement yourself, it is advisable to seek professional assistance. A licensed HVAC technician can quickly and efficiently replace the contactor on your AC unit, ensuring that your system operates at its best.

Regular maintenance and prompt repairs are essential to keep your air conditioning unit operating smoothly. By addressing issues such as a faulty contactor, you can ensure the comfort and efficiency of your home's cooling system for years to come.


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