how to tell if my ac contactor is bad


Signs That Your AC Contactor May Be Malfunctioning

Is your air conditioner not cooling your home like it used to? Are you experiencing electrical issues and suspect that your AC contactor might be to blame? The AC contactor is a crucial component of your air conditioning system responsible for controlling the flow of electricity to the unit's compressor and condenser fan motor. When it becomes faulty, it can disrupt the normal functioning of your AC system, leading to various issues. In this article, we will delve into the signs that indicate a potential problem with your AC contactor and discuss the steps you can take to troubleshoot and address the issue.

Strange Noise or Buzzing Sound

One of the noticeable indications of a bad AC contactor is the presence of strange noises or buzzing sounds originating from your air conditioning unit. When the contactor is not functioning correctly, it can cause the electrical current to arc or make loose connections, resulting in a buzzing or clicking sound. These sounds can be especially prominent when the contactor is energized, i.e., when your AC system is running. Pay close attention to any abnormal noises coming from your unit, as they can be an early warning sign of a failing contactor.

If you suspect that the noise is coming from your AC contactor, it is essential to address it promptly. Ignoring the issue or delaying repairs can lead to further damage to other components of your air conditioning system, potentially resulting in the need for costly repairs or even a complete system replacement.

Frequent Cycling On and Off

Another telltale sign of a faulty AC contactor is frequent cycling of your air conditioner. When the contactor is not functioning correctly, it can cause your AC unit to turn on and off rapidly and more frequently than usual. This can be highly inconvenient and frustrating, as it not only affects the efficiency of your cooling system but also puts unnecessary strain on the unit, reducing its lifespan.

The frequent cycling can occur for several reasons. One possibility is a corroded or pitted contactor, which prevents it from making a proper connection. As a result, the contactor may repeatedly engage and disengage, causing the AC unit to cycle on and off. Another reason for this issue could be a contactor that remains stuck in the closed position, causing the compressor to continuously run without interruption. Both scenarios indicate an issue with the AC contactor that requires attention.

Failure of the Condenser Fan to Start

If your air conditioner's condenser fan fails to start or exhibits intermittent operation, a malfunctioning contactor may be the culprit. The contactor is responsible for supplying power to the condenser fan motor, which works in tandem with the compressor to expel heat from your home. When the contactor fails to deliver the required voltage to the fan motor, it can lead to improper cooling and increased temperatures.

To determine if the contactor is to blame for the condenser fan's failure to start, you can perform a simple visual inspection. Start by turning off the power to your air conditioning system and carefully remove the access panel to the condenser unit. Locate the contactor, which resembles a small box with several wires connected to it. Examine the contacts for signs of burning, pitting, or corrosion. Additionally, inspect the fan motor blades, ensuring there is no obstruction or physical damage. If the contactor shows visible damage or the blades are obstructed, it may be time to replace the contactor.

Failure of the Compressor to Start

The compressor is the heart of your air conditioning system, responsible for circulating the refrigerant and ensuring proper heat transfer. However, if your compressor fails to start, it could indicate a problem with the AC contactor. When the contactor fails, it hinders the flow of electricity to the compressor, preventing it from starting and thus inhibiting the cooling process.

To check if a malfunctioning contactor is responsible for the compressor failure, you can conduct a visual inspection similar to the one described earlier for the condenser fan. Look for any visible signs of damage or wear on the contactor's contacts. Additionally, examine the area around the compressor for signs of burned wires or a melted appearance. If any abnormalities are present, it is crucial to replace the contactor to restore proper functioning to your air conditioning system.

Difficulty in Turning On the AC Unit

A malfunctioning AC contactor can also manifest as difficulty in turning on your air conditioning unit. When you experience trouble initiating your AC system, it often points to a faulty contactor that is unable to establish the necessary electrical connections to start the unit. This can be a frustrating issue, leaving you without a functioning air conditioner during hot summer days.

If you encounter difficulties in turning on your AC unit, there are a few steps you can take to troubleshoot the issue. Start by checking the circuit breaker or fuse box to ensure that no fuses have blown or breakers have tripped. If this appears to be in order, move on to inspecting the contactor. Look for any visible signs of damage, wear, or loose connections. Ensure that the contacts are clean and free from debris. If you notice any issues, such as burned or pitted contacts, it is advisable to replace the contactor to restore proper functionality to your AC unit.


Identifying potential issues with your AC contactor is crucial in maintaining the optimal performance of your air conditioning system. By paying attention to the signs mentioned above, you can detect a malfunctioning contactor early on and resolve the issue before it leads to further damage or complete system failure. If you encounter any of these signs, it is recommended to consult with a professional HVAC technician who can diagnose the problem accurately and provide the necessary repairs or replacements. Remember, regular maintenance and timely repairs are key to ensure the longevity and efficiency of your air conditioning system.


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