how to check the ac contactor


The Importance of Checking the AC Contactor

As the summer approaches, ensuring that your air conditioning system is in good working condition becomes crucial. One crucial component of an AC system is the contactor, which plays a vital role in controlling the flow of electricity to the compressor and fan motor. Over time, contactors can experience wear and tear, potentially leading to malfunctions or breakdowns in your cooling system. Therefore, regularly checking the AC contactor is essential to maintain the efficiency and reliability of your AC unit. In this article, we will guide you through the process of checking the AC contactor, enabling you to keep your cooling system functioning optimally throughout the summer months.

Understanding the AC Contactor

Before we delve into the process of checking the AC contactor, it is important to gain a basic understanding of what a contactor is and how it functions within an air conditioning system. A contactor is an electrical component that acts as a switch to control the flow of electricity to the compressor and fan motor. It is responsible for engaging the compressor and fan motor, initiating the cooling process. When the desired temperature is reached, the contactor disengages the compressor and fan motor, halting the cooling cycle.

Determining When to Check the AC Contactor

Regularly inspecting and evaluating the AC contactor is crucial to ensuring the overall functionality and longevity of your air conditioning system. However, certain warning signs indicate that it is imperative to check the AC contactor immediately. Pay attention to the following indicators:

1. Subpar Cooling Performance

If you notice a decrease in cooling performance, such as the air conditioner not reaching the desired temperature or the cold air not circulating effectively, it may indicate a faulty contactor. The contactor's failure to engage the compressor and fan motor properly can significantly impact the cooling capacity of your AC system.

2. Frequent System Cycling

If your air conditioning system is cycling on and off more frequently than usual, it may suggest a malfunctioning contactor. The contactor's failure to maintain a stable connection can lead to short cycling, causing unnecessary wear and tear on your cooling system.

3. Unusual Noises

Unusual sounds coming from your AC system, such as buzzing or humming, can indicate a faulty contactor. These noises may occur when the contacts within the contactor are deteriorating or not making proper contact, leading to electrical arcing.

4. Damaged Contacts

Inspecting the contacts within the AC contactor is an essential part of regular maintenance. By removing the access panel of your air conditioning unit, you can visually inspect the contacts for signs of wear, pitting, or burning. Damage to the contacts may result from electrical arcing or general deterioration over time.

5. Age of the Air Conditioning System

Finally, it is important to consider the age of your air conditioning system. If your system is over ten years old, it may be more susceptible to contactor issues due to wear and tear. Regularly checking the contactor can help identify any potential problems and extend the lifespan of your AC unit.

Checking the AC Contactor

Now that we have established the importance of checking the AC contactor and identified potential warning signs, let us explore the step-by-step process of inspecting and evaluating the contactor.

1. Safety Precautions

Before beginning any maintenance or inspection work, it is crucial to ensure your safety. Make sure to turn off the power supply to the air conditioning system by flipping the corresponding circuit breaker in your electrical panel. This precautionary step will protect you from any potential electrical hazards during the inspection process.

2. Accessing the Contactor

To access the AC contactor, you will need to remove the access panel located on the outside unit of your air conditioner. The access panel is generally secured with screws or latches and may require a screwdriver or wrench to open. Once the panel is removed, you will have a clear view of the contactor and other essential components.

3. Visual Inspection

Begin by visually inspecting the contactor for any obvious signs of damage or wear. Look for melted plastic, burned components, loose wires, or excessive dirt. These visual cues can help identify potential issues that require further inspection or professional assistance.

4. Contact Condition

Carefully examine the condition of the contactor's contacts. Look for signs of pitting, burning, or deterioration. If the contacts appear damaged, it is recommended to replace the contactor with a new one. Damaged contacts can hinder the flow of electricity and affect the overall functionality of your air conditioning system.

5. Electrical Testing

After the visual inspection, it is essential to perform electrical testing to ensure the contactor is functioning correctly. With a multimeter set to the resistance or continuity setting, test the contactor's coil by placing the meter leads on the coil terminals. A properly functioning coil should provide a continuous circuit, indicating that power can flow through it. If the multimeter reading shows infinite resistance or no continuity, it may suggest a faulty coil that requires replacement.

6. Checking for Proper Engagement

To verify the contactor's engagement, you can manually press down on the contactor's central bar while the power supply is turned off. This action should make a distinct clicking sound as the contacts engage. Release the bar, and the contacts should disengage with another clicking sound. If you do not hear these clicking sounds or notice any hesitation in the movement of the contacts, it may indicate a defective contactor.


Checking the AC contactor is an essential maintenance task that should be performed regularly to ensure the efficient and reliable operation of your air conditioning system. By understanding the role of the contactor, recognizing warning signs, and following a systematic inspection process, you can identify any issues promptly and take necessary measures to rectify them. Remember to prioritize safety and consult a professional if you feel unsure about performing any electrical testing or if you encounter significant damage. Regular maintenance and care will contribute to extending the lifespan of your AC unit and ensuring your comfort during the scorching summer months.


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