how to tell if you have a bad ac contactor


Signs That Indicate a Bad AC Contactor

Is your air conditioner not functioning properly? Are you experiencing inconsistent cooling or unusual noises coming from your unit? If so, it is possible that your AC contactor may be to blame. The AC contactor is an essential component of your air conditioning system that controls the flow of electrical current to the compressor and fan motor. When it becomes faulty, it can lead to a variety of issues that may affect the performance of your AC unit. In this article, we will explore the signs that indicate a bad AC contactor, helping you to identify and resolve the problem promptly.

Strange Noises

One of the most common signs of a faulty AC contactor is strange noises coming from your air conditioning unit. If you notice buzzing, humming, or clicking noises that were not present before, it is likely that there is a problem with the contactor. These unusual sounds can occur when the contactor contacts are corroded or damaged, preventing them from making proper electrical connections. As a result, the contactor may be struggling to send the correct electrical signals to the compressor and fan motor, leading to the abnormal noises. If you encounter such noises, it is recommended to have your contactor inspected by a professional technician to determine the extent of the damage and prevent further issues from arising.

Intermittent Cooling

When your AC contactor is malfunctioning, you may experience intermittent cooling or inconsistent temperatures in your home. The contactor's primary function is to control the flow of power to the compressor, which is responsible for cooling the refrigerant and maintaining the desired temperature. If the contactor fails to provide a stable electrical connection, the compressor may not receive the necessary power to function correctly. As a result, you may notice that your air conditioner cools your space erratically or struggles to maintain the desired temperature. If you encounter this issue, it is crucial to address it promptly as prolonged use of a faulty contactor can lead to further damage to your AC system and higher repair costs.

Failure to Start

Another clear indication of a bad AC contactor is a failure to start. If you find that your air conditioner does not turn on when you adjust the thermostat, it may be due to a faulty contactor. The contactor is responsible for completing the circuit and supplying the necessary power to start the compressor and fan motor. When the contactor is defective, the electrical current may not flow smoothly, preventing the system from starting up. This can be a frustrating situation, especially during hot summer days when you are reliant on your air conditioner for comfort. In such cases, it is advisable to seek professional assistance to diagnose and replace the faulty contactor.

Constantly Running Fan

A constantly running fan is another symptom of a bad AC contactor. Typically, the fan motor should only run when the compressor is operating and actively cooling the air. However, if the contactor fails to send the correct electrical signals, the fan motor may continue to run even when the compressor is not. This can result in wasted energy and increased utility bills. Moreover, the constant operation of the fan motor can also cause it to wear out prematurely, leading to further repair expenses. If you notice that your fan is running continuously, it is vital to have your contactor inspected and replaced if necessary.

Hot Contactors

One of the most straightforward signs of a problematic AC contactor is the presence of excessively hot contactors. The contactors in your air conditioning system may become overheated if the electrical current is not flowing properly. When this occurs, it is often an indication of loose connections or corrosion on the contactor contacts, hindering its ability to transmit electricity efficiently. Hot contactors not only indicate a faulty contactor but can also pose a fire hazard if left unaddressed. Therefore, if you find that your contactor is excessively hot to the touch, it is crucial to turn off the system immediately and seek the assistance of an HVAC professional to resolve the issue.


In conclusion, a malfunctioning AC contactor can significantly impact the performance and functionality of your air conditioning system. If you notice any signs of a faulty contactor, such as strange noises, intermittent cooling, failure to start, constantly running fan, or hot contactors, it is essential to address the issue promptly. Contacting a professional HVAC technician is recommended to diagnose the problem accurately and ensure the correct replacement of the faulty contactor. By taking swift action, you can prevent further damage to your AC system and enjoy a cool and comfortable indoor environment once again.


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