how to tell if your ac contactor is bad


What Is an AC Contactor?

An AC contactor, also known as an air conditioner contactor, is a crucial component in your AC system. It acts as a switch that controls the flow of electricity between the power source and the compressor and fan motor. When the thermostat signals the need for cooling, the contactor allows electricity to flow, activating the compressor and fan motor to start the air conditioning process.

Similar to any other electrical component, an AC contactor can deteriorate over time due to wear and tear, leading to potential malfunctions. Issues with the contactor can cause your AC system to malfunction or cease working altogether. Therefore, it is essential to be able to identify signs of a bad AC contactor to ensure the smooth operation of your air conditioning unit and to avoid costly repairs. In this article, we will discuss various indicators that help you determine if your AC contactor is faulty.

Common Signs of a Bad AC Contactor

If your AC contactor is experiencing problems, it is likely to exhibit one or more of the following signs:

1. Constant Clicking Noise

A continuously clicking noise that emanates from your AC unit is an indication of a faulty contactor. The contactor's primary function is to switch the AC system on and off. When the contactor is damaged or worn out, it may struggle to complete this process smoothly. As a result, you may hear a rapid clicking sound, indicating that the contactor is attempting to engage but is unable to do so effectively.

It is important to address this issue promptly, as constant clicking can put a strain on other AC components, potentially causing further damage. Furthermore, a malfunctioning contactor will prevent your AC system from functioning correctly, resulting in poor cooling performance.

2. Failure to Start

When your air conditioning system fails to start or experiences intermittent start-up delays, it may be a sign of a defective contactor. A bad contactor might struggle to close or make proper contact, preventing the flow of electricity to the compressor and fan motor. In such cases, your AC unit may attempt to start and then shut down soon after or refuse to start altogether.

If you notice this symptom, it is advisable to consult a professional HVAC technician to diagnose and rectify the problem. Delaying repairs can lead to increased wear on other components and potentially further damage to the AC system.

3. AC Unit Not Cooling

A malfunctioning AC contactor can cause your air conditioning unit to stop cooling effectively. If the contactor is unable to switch on the compressor and fan motor, your AC system will not be able to generate cool air. This can result in decreased airflow, lukewarm air blowing from the vents, or even no airflow at all.

In such cases, it is vital to have your AC contactor inspected and, if necessary, replaced to restore proper functioning. Attempting to fix the contactor yourself without adequate knowledge and experience can be dangerous, so it is best to consult a professional technician for any required repairs.

4. Frequent Electrical Issues

Another telltale sign of a bad AC contactor is the presence of frequent electrical issues in your home. A faulty contactor can cause voltage fluctuations and fluctuations in the electrical current supplied to your air conditioning system. This can lead to flickering lights, tripped circuit breakers, or even electrical surges, which may damage other sensitive electronic devices connected to the same power supply.

If you notice these electrical issues in combination with any of the other symptoms mentioned in this article, it is crucial to have your AC contactor inspected by a professional technician. They can determine if the contactor is the root cause of the electrical problems and take appropriate action to fix the issue.

5. Burn Marks or Damage

Physical inspection of your AC contactor can provide valuable insights into its condition. Over time, contactors can experience wear and tear, resulting in visible damage or burn marks on the contact points. Burn marks are an indication that the contactor may be arcing or not making proper contact, reducing its efficiency.

When inspecting your AC contactor, ensure that the power to the unit is turned off to prevent any electrical accidents. If there are visible signs of damage or burn marks, it is essential to replace the faulty contactor to prevent further issues and potential damage to your air conditioning system.


Being able to recognize the signs of a bad AC contactor is crucial for maintaining the optimal performance of your air conditioning unit. Constant clicking noises, failure to start, inadequate cooling, frequent electrical issues, and physical damage are all indicators of a potential contactor malfunction. It is essential to address these problems promptly to avoid further damage to your HVAC system and to prevent discomfort in your living space.

If you suspect that your AC contactor is faulty, it is recommended to consult a professional HVAC technician for an accurate diagnosis and appropriate repairs. A trained technician will have the necessary expertise to identify the problem and ensure your AC system is back to providing cool and comfortable air in no time.

Remember, regular maintenance of your HVAC system is crucial to prevent most issues, including contactor failures. Engaging in routine inspections and cleaning of your AC unit can help identify potential problems early on, allowing for timely repairs or part replacements. By taking proper care of your AC contactor and other components, you can prolong the lifespan of your air conditioning system while ensuring optimal performance throughout.


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