how to replace contactor on trane ac unit


How to Replace Contactor on Trane AC Unit

Is your Trane AC unit acting up? Have you noticed that it's not cooling your home as effectively as before? One common issue that can arise with an AC unit is a faulty contactor. The contactor is a crucial component that controls the electrical current flow to the compressor and condenser fan motor. When it malfunctions, it can lead to a variety of AC problems. In this article, we will guide you through the process of replacing the contactor on your Trane AC unit, ensuring that your AC system operates efficiently once again. So, let's dive right in!

Understanding the Contactor and its Importance

Before we begin discussing how to replace the contactor, it's essential to understand what it is and why it's crucial to the functioning of your Trane AC unit. The contactor is a type of electrical switch that controls the flow of electricity to the compressor and condenser fan motor. It acts as a bridge between the thermostat and the actual electrical current that powers these components.

The contactor consists of a coil and several sets of contacts. When the thermostat signals the need for cooling, the coil in the contactor is energized, causing the contacts to close. This allows the electricity to flow from the power source to the compressor and condenser fan motor, ultimately leading to the cooling process.

Signs of a Faulty Contactor

Identifying a faulty contactor is the first step in the replacement process. Several signs can indicate that your Trane AC unit's contactor is not functioning correctly:

1. AC Unit Not Cooling: If your AC unit is running, but you're not feeling any cool air, a faulty contactor could be to blame. When the contactor fails, it may prevent power from reaching the compressor and condenser fan motor, resulting in a lack of cooling.

2. Frequent Cycles: Are you noticing that your AC unit is turning on and off more frequently than usual? This can be an indication of a malfunctioning contactor. The contactor may be failing to maintain a consistent electrical current, causing the system to cycle irregularly.

3. Noise and Vibrations: A worn-out or damaged contactor can produce strange noises or vibrations when the AC unit is operating. If you're hearing unusual buzzing, clicking, or humming sounds, it's worth investigating the contactor as a potential issue.

4. Burn Marks or Damage: Sometimes, a visual inspection can reveal signs of a faulty contactor. Look for burn marks or physical damage on the contactor itself. If you notice any, it's a clear indication that the contactor needs to be replaced.

5. AC Unit Not Powering On: In the worst-case scenario, a completely failed contactor may lead to the AC unit not turning on at all. If you've ruled out other potential causes and your AC remains unresponsive, the contactor should be examined.

Gathering Tools and Materials

Now that you've identified that the contactor is indeed the issue, you'll need to gather a few tools and materials before diving into the replacement process. Here's what you'll need:

1. Safety Gear: It's essential to prioritize your safety while working with electrical components. Wear insulated gloves, safety glasses, and long sleeves to protect yourself from potential hazards.

2. Screwdriver: You'll need a screwdriver to remove the contactor's access panel and to disconnect the wires from the old contactor.

3. New Contactor: Purchase a replacement contactor that is compatible with your Trane AC unit model. Refer to your unit's manual or contact a professional to ensure you select the correct part.

4. Wire Labeling: To avoid confusion during the replacement process, use labels or markers to mark each wire's location and corresponding terminal on the old contactor.

5. Camera or Phone: Taking pictures of the original wiring configuration can provide a helpful reference when connecting the wires to the new contactor.

Replacing the Contactor

With your tools and materials ready, let's move on to the step-by-step process of replacing the contactor on your Trane AC unit:

1. Turn Off the Power: Before starting any work, make sure to turn off the power supply to the AC unit. Locate your main electrical panel and switch off the breaker that controls the AC unit. To be safe, you may want to test that the power is truly off by attempting to turn on the AC unit after shutting off the breaker.

2. Remove the Access Panel: Using your screwdriver, carefully remove the access panel on the AC unit. This panel is typically located on the side or top of the unit and may require removing a few screws.

3. Take a Picture of the Wiring: Take clear pictures of the wiring configuration of the old contactor. This will serve as a visual reference when connecting the wires to the new contactor later on.

4. Disconnect Wires from Old Contactor: Carefully disconnect the wires from the old contactor, ensuring that you remember the location of each wire. If necessary, use your wire labels or markers to identify which wire connects to each terminal.

5. Remove Old Contactor: Unscrew and remove the old contactor from its mounting bracket. Take note of how the contactor was positioned and make sure to install the new contactor in the same orientation.

6. Install New Contactor: Position the new contactor on the mounting bracket, aligning it correctly. Secure it in place using the screws provided or the ones removed from the old contactor.

7. Connect Wires to New Contactor: Referencing the pictures you took earlier, connect each wire to its corresponding terminal on the new contactor. Double-check that the connections are secure and tight.

8. Replace Access Panel: Place the access panel back onto the AC unit and fasten it with the screws you initially removed. Ensure that the panel is properly aligned and tightly secured.

9. Turn on the Power: Return to the main electrical panel and switch the breaker back on, restoring power to the AC unit. Wait for a few moments to see if the AC unit starts up and operates correctly.

Congratulations! You have successfully replaced the contactor on your Trane AC unit. Take a moment to test the AC's functionality and listen for any unusual noises or vibrations. If everything appears to be in order, you can rest assured that you've resolved the contactor issue and restored your AC unit's performance.


In conclusion, a faulty contactor can disrupt the proper functioning of your Trane AC unit. Fortunately, replacing it is a relatively straightforward process that can be done with a few basic tools and minimal experience. By following the step-by-step instructions outlined in this article, you can confidently replace the contactor yourself, saving both time and money. Remember to prioritize your safety and consult a professional if you feel uncomfortable with any aspect of the replacement process. With a new contactor in place, your Trane AC unit should cool your home efficiently once again, ensuring a comfortable living space for you and your family.


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