how to check if ac contactor is bad


How to Check if AC Contactor is Bad


An air conditioner relies on numerous components to function optimally, and the AC contactor is an essential part of this system. The AC contactor is responsible for controlling the flow of electricity to various parts of the air conditioner, including the compressor, fan motor, and condenser. Over time, the contactor can become worn out or damaged, leading to issues with the air conditioner's performance. In this article, we will discuss how to determine if the AC contactor is bad and what steps you can take to diagnose and fix the problem.

Common Symptoms of a Bad AC Contactor

When the AC contactor starts to fail, it can exhibit certain symptoms that indicate its deterioration. By being aware of these signs, you can identify whether or not the AC contactor is the culprit behind your air conditioner's problems.

1. Irregular Cooling or Heating

If you notice that your air conditioner is not providing the desired cooling or heating, the faulty AC contactor might be to blame. When the contactor is damaged, it can disrupt the flow of electricity to the compressor, impacting its ability to cool or heat the air effectively. Consequently, you may observe inconsistent temperature levels in your home or office.

When you encounter this issue, it is crucial to examine other potential causes as well. Issues such as low refrigerant levels, dirty filters, or malfunctioning thermostats could also result in irregular cooling or heating. However, if none of these common culprits seem to be responsible, inspecting the AC contactor is an important step in troubleshooting.

2. Frequent On and Off Cycling

Another symptom of a failing AC contactor is when the air conditioner constantly cycles on and off. This rapid and frequent cycling not only hampers the unit's performance but also places extra strain on the system's components, potentially leading to further damage and energy waste.

When the AC contactor weakens, it can cause the air conditioner to lose the ability to maintain a consistent electrical connection. As a result, the unit may continuously turn on and off in short intervals. If you notice this irregular operation pattern, it is advisable to check the AC contactor for any signs of degradation.

3. Abnormal Noise

Unusual sounds coming from your air conditioner can often indicate a faulty component, and the AC contactor is no exception. When the contactor starts to fail, it may produce clicking or buzzing sounds as it tries to engage or disengage the electrical circuit. These sounds can be a result of loose contact points or damaged wiring within the contactor.

It is vital to pay attention to any changes in the normal operating noise of your air conditioner, as it can help you identify potential issues before they escalate. If you hear distinctive sounds such as clicking or buzzing, it is advisable to inspect the AC contactor for possible damage.

4. Burnt or Pitted Contacts

One of the most apparent visual signs of a bad AC contactor is burnt or pitted contacts. Over time, the electrical current flowing through the contacts can generate heat, leading to damage and deterioration. Visual inspection of the contactor can reveal blackened or charred contact points, indicating that the contacts are no longer making proper contact.

To inspect the contacts, ensure that the power supply to the air conditioner is turned off. Then, open the electrical panel and locate the contactor. Examine the contacts for any signs of discoloration, burning, or pitting. If you notice significant damage, it is a clear indication that the AC contactor needs to be replaced.

5. Insufficient Power Supply

When the AC contactor is malfunctioning, it may not be able to provide an adequate power supply to other components of the air conditioner. As a result, the system may fail to function entirely or may exhibit reduced performance. This lack of power can affect the efficiency and effectiveness of the cooling or heating process.

If you are facing issues with your air conditioner not starting at all, or if it fails to blow out cold or hot air as expected, it is essential to investigate whether the AC contactor is the cause of the problem. By ensuring that the contactor is receiving the necessary electrical supply and delivering it to the other components, you can rule out this potential issue.

Steps to Check if the AC Contactor is Bad

Determining whether the AC contactor is the cause of your air conditioner's problems requires a step-by-step approach. By following these steps, you can effectively check the condition of the contactor and evaluate if it needs to be replaced.

1. Ensure Safety Precautions

Before proceeding to examine the AC contactor, it is crucial to prioritize safety. Since your air conditioner involves electrical components, there may be risks of electric shock. Therefore, it is vital to turn off the power supply to the unit by shutting off the circuit breaker in your electrical panel. To be safe, double-check that there is no power flowing to the air conditioner before proceeding with the inspection.

2. Remove the Contactor Cover

Once you have ensured the power is turned off, locate the contactor in your air conditioning unit. The contactor is usually located inside the electrical panel, which is typically situated near the compressor unit outside your home. Remove the screws or bolts securing the cover of the contactor, allowing you access to the internal components.

3. Inspect the Contactor

With the contactor cover removed, visually inspect the contactor for any signs of damage or wear. Pay close attention to the contacts, looking for burnt or pitted surfaces. If you notice any significant damage, it is a clear indication of a bad contactor that needs to be replaced.

4. Perform a Voltage Test

To further confirm if the AC contactor is the cause of the issue, you can perform a voltage test using a multimeter. Set the multimeter to the voltage setting recommended for testing 240V AC. After ensuring that the power is turned off, carefully test the voltage on both the line side (incoming power) and the load side (outgoing power) of the contactor.

5. Analyze the Test Results

After performing the voltage test, compare the results with the manufacturer's specifications. If you do not get any voltage readings on either side of the contactor, it might be an indication that the contactor is faulty and needs to be replaced. However, if there are voltage readings on one side and not the other, it could suggest a problem with the contactor or another electrical component.


The AC contactor plays a crucial role in the proper functioning of an air conditioner. By paying attention to common symptoms like irregular heating or cooling, frequent cycling, abnormal noise, burnt contacts, or insufficient power supply, you can identify potential issues with the contactor. By carefully inspecting the contactor and performing a voltage test, you can determine whether the AC contactor requires replacement. Remember, safety should always be a priority when working with electrical components, so make sure to turn off the power supply and seek professional assistance if needed. Regular maintenance and timely repairs will help ensure the prolonged efficiency and reliability of your air conditioning unit.


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