how to fix contactor on ac unit



Contactor issues are a common problem that can occur in air conditioning (AC) units. If your AC unit is not working properly, it might be due to a faulty contactor. The contactor is an essential component that controls the flow of electricity to the various parts of the AC unit. When it malfunctions, it can lead to a variety of problems, such as the unit not turning on, not cooling effectively, or continuously running. In this article, we will discuss the steps on how to fix a contactor on an AC unit, ensuring your system runs smoothly and efficiently.

Common Signs of a Faulty Contactor:

Before diving into the steps on how to fix a contactor on an AC unit, it's important to recognize the common signs of a faulty contactor. This will help you diagnose the issue and confirm whether the contactor is indeed the problem. Here are some signs to look out for:

1. Clicking Sound: One of the first indications of a faulty contactor is hearing a repetitive clicking sound when the unit tries to start. This sound usually signifies that the contactor is trying to close but is unable to do so properly.

2. Unit Not Turning On: Another significant sign of a faulty contactor is when your AC unit fails to turn on despite it being properly connected to a power source. This could be due to a contactor that is stuck in the open position, preventing electricity from flowing to the unit.

3. Inconsistent Cooling: If you notice that your AC unit's cooling performance has become inconsistent, it could be a result of a faulty contactor. When the contactor is not functioning correctly, it may not allow enough power to reach the compressor, causing inefficient cooling.

4. Continuous Running: A contactor that is stuck in the closed position can cause the AC unit to run continuously, even when it is not necessary. This can lead to excessive wear and tear on the unit and higher energy bills.

5. Burning Smell or Visible Damage: In some cases, a faulty contactor may exhibit visible damage such as burnt or melted components. If you detect a burning smell or any visible damage, it is crucial to address the issue promptly to avoid further damage to the unit.

Now that we have explored the common signs of a faulty contactor, let's move on to the steps on how to fix the contactor on an AC unit.

Gathering the Necessary Tools:

Before you begin working on the contactor, it is essential to gather the necessary tools to ensure a smooth repair process. Here are some tools you may need:

1. Screwdriver set

2. Voltage tester

3. Wire strippers

4. Insulating tape

5. Replacement contactor (if needed)

1. Turn Off the Power:

The first step in fixing a contactor on an AC unit is to ensure your safety by turning off the power. Locate the electrical disconnect box or panel near your outdoor AC unit, usually mounted on the wall. Open the panel and switch off the power supply by flipping the corresponding circuit breaker to the "off" position. For added safety, use a voltage tester to confirm that no power is flowing to the unit before proceeding further. Safety should be the top priority when working with electrical components.

2. Remove the Access Panel and Locate the Contactor:

Once you have turned off the power, remove the access panel on the AC unit to gain access to the internal components. The location of the contactor may vary depending on the specific AC unit model. However, it is commonly found near the compressor in the outdoor unit. The contactor is a rectangular-shaped component with multiple wires attached to it.

3. Test the Contactor:

After locating the contactor, it is crucial to test it before proceeding with the repair. Use a voltage tester to check if power is flowing through the contactor. Place the voltage tester on the contact points of the contactor and observe the reading. If the voltage tester shows no power, it indicates that the contactor is not functioning correctly and needs to be replaced. In contrast, if there is power, further troubleshooting may be required to identify other potential issues.

4. Disconnect Wires and Remove the Defective Contactor:

To remove the faulty contactor, start by carefully disconnecting all the wires connected to it. Take note of the wire placements to ensure proper reinstallation later. Depending on the AC unit model, you might need to use a screwdriver to remove the contactor from the mounting bracket. Set aside the defective contactor, as it will be replaced in the next step.

5. Install the New Contactor:

With the faulty contactor removed, it's time to install the new one. Begin by placing the new contactor in the same position and aligning it with the mounting bracket. Next, reconnect all the wires to the appropriate terminals of the new contactor, referring to the notes made during the removal process. Ensure that the wires are securely fastened to prevent any loose connections.

6. Inspect and Test:

Before closing the access panel, take a moment to inspect all the connections and ensure they are properly tightened. Loose connections can cause issues with the contactor's functionality, so it's essential to double-check everything. Once you are satisfied with the connections, close the access panel and proceed to turn the power back on.


Fixing a contactor on an AC unit can be a relatively straightforward process, provided you follow the necessary steps and take the required safety precautions. Remember to always turn off the power before starting any repair work and use a voltage tester to confirm that the unit is indeed powered off. By identifying the signs of a faulty contactor, gathering the necessary tools, and following the step-by-step process described in this article, you can successfully replace a defective contactor and restore your AC unit's functionality. If you are unsure or uncomfortable performing the repair yourself, it is always advisable to seek professional assistance to ensure the job is done correctly and safely.


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