why won't my ac contactor pull in


Why Won't My AC Contactor Pull In?


Has your air conditioning system stopped working suddenly? Are you wondering why your AC contactor won't pull in and what you can do to fix it? This article aims to provide you with a comprehensive understanding of this common issue faced by homeowners. By delving into the reasons behind a malfunctioning AC contactor, we will guide you through troubleshooting steps and potential solutions to get your air conditioning system up and running again.

The Role of the AC Contactor

The AC contactor plays a crucial role in the functioning of your air conditioning system. It is an electromagnetic switch responsible for controlling the flow of electrical current to the compressor, fan motor, and condenser unit. When the thermostat signals the need for cooling, the AC contactor engages to power these components, allowing your system to operate efficiently. However, when the contactor fails to pull in, it interrupts the electrical circuit and prevents the system from functioning altogether.

Causes of a Contact Failure

Various factors can lead to an AC contactor failing to pull in. Identifying the root cause is key to finding the appropriate solution and preventing further damage to your system. Here are some common causes to consider:

1. Faulty Contactor Coil:

The contactor coil is an electromagnet that activates when current flows through it. Over time, this coil can become damaged or worn out, hindering its ability to pull the contactor in. Excessive electrical arcing, voltage fluctuation, and wear and tear are common culprits behind a faulty contactor coil.

One way to determine if the coil is defective is by using a multimeter to measure the resistance across its terminals. If the reading is significantly different from the manufacturer's specifications, it's time to replace the coil.

2. Contactor Pitting or Burnout:

Exposure to moisture, dirt, and electrical arcing can cause pitting and burnout on the contactor points. This prevents proper contact and results in the contactor's failure to pull in. Insufficient maintenance, such as neglecting to clean or lubricate the contactor regularly, can contribute to these issues.

Inspect the contactor points for signs of pitting or burnout using a flashlight. If you notice any damage, it may be necessary to replace the contactor entirely.

3. Weak or Damaged Contactor Spring:

The contactor spring provides the necessary tension for the contacts to close firmly. If the spring weakens or becomes damaged, it may not generate enough force to pull the contactor in, leading to a system failure.

To check the spring's condition, disconnect the power and safely remove the cover of the contactor. Inspect the spring visually for any signs of damage or wear. If necessary, replace the spring with a new one from the manufacturer.

4. Electrical Power Issues:

Issues with the electrical power supply to your air conditioning system can also prevent the contactor from pulling in. Ensure that the circuit breaker for your HVAC unit is not tripped and that the fuses in your electrical panel are intact. Faulty wiring or loose connections between the electrical panel and the contactor can also disrupt the electrical flow.

If you suspect an electrical power issue, it's recommended to consult a professional electrician to diagnose and resolve the problem.

5. Defective Control Board:

In some cases, the root cause of a contactor failure lies with the control board within the air conditioning system. If the control board is malfunctioning or suffers from a faulty relay, it may not send the appropriate signal to engage the contactor.

Testing the control board requires specialized equipment and knowledge, making it advisable to seek professional assistance to diagnose and replace the defective components.

Troubleshooting Steps

Before calling a professional technician, you can perform a few troubleshooting steps to potentially rectify the issue with your AC contactor. However, always prioritize your safety and disconnect the power to the system before attempting any troubleshooting steps.

1. Clean and Inspect:

Start by visually inspecting the contactor for any noticeable signs of damage, such as burn marks or corrosion. Use a soft brush or compressed air to remove any debris or dirt buildup. Ensure that the contacts are clean and free from pitting or carbon deposits.

2. Check Voltage:

Using a multimeter, establish whether your contactor is receiving the required voltage. Test the voltage at the contactor coil terminals. If the voltage is below the manufacturer's specified range, it may indicate an issue with the power supply or control board.

3. Test the Coil:

Measure the resistance across the coil terminals using a multimeter. Compare the reading to the manufacturer's provided range. If the resistance is significantly different, it may indicate a faulty coil that needs replacement.

4. Inspect Wiring and Connections:

Examine the wiring connections to ensure they are secure and free from corrosion. Tighten any loose connections and replace any damaged or frayed wires.

5. Verify the Thermostat:

Ensure that the thermostat settings are correctly configured for cooling mode. Test the thermostat's functionality by lowering the temperature setting to trigger the system. If the thermostat is not functioning correctly, it may not be sending the signal to engage the contactor.


A malfunctioning AC contactor can be a frustrating issue that disrupts your air conditioning system's operation. By understanding the various causes for a contactor failure, you can troubleshoot the problem and potentially resolve it yourself. However, it is crucial to prioritize your safety and seek professional assistance if you encounter complexities during the troubleshooting process. Remember to perform regular maintenance on your air conditioning system to prevent contactor issues and ensure it operates efficiently and reliably.


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