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How To Check Contactor On Ac Unit?




Does your AC unit seem to be malfunctioning?

To check the contactor on an AC unit, follow these steps:

1. Turn off the power: Before starting, ensure the power to the AC unit is turned off. Switch off the circuit breaker or disconnect the power supply to the unit.

2. Locate the contactor: Open the AC unit’s access panel and locate the contactor, which is typically a small box with wires connected to it. It is usually near the compressor and condenser fan motor.

3. Visual inspection: Check for any visible signs of damage, such as burnt or melted components, discolored contacts, or loose connections. If you notice any of these issues, the contactor may need to be replaced.

4. Check for proper voltage: Use a multimeter to measure the voltage across the contactor’s coil terminals. The reading should be within the specified range, typically 24 volts. If the voltage is too low or not present, there may be an issue with the control circuit or transformer.

5. Test for continuity: Set the multimeter to the continuity setting and test the contactor’s contacts. Place the probes on the input (line) and output (load) terminals. If the contactor is functioning correctly, you should hear a beep or see a reading close to zero when the contactor is energized. If not, the contacts may be damaged or worn, and the contactor should be replaced.

6. Check for proper operation: Turn the power back on and observe the contactor as the AC unit starts. The contactor should engage (pull in) when the thermostat calls for cooling and disengage (drop out) when the thermostat is satisfied. If the contactor does not operate as expected, it may be faulty and require replacement.

How To Check Contactor On Ac Unit?

If you are not comfortable performing these tests or if you are unsure about any of the steps, it is recommended to consult a professional HVAC technician to check the contactor for you.

One of the potential culprits could be a faulty contactor.

The contactor is responsible for powering the compressor and fan motor in your AC unit, so it’s important to know how to check it when troubleshooting issues.

Fortunately, checking your contactor isn’t too difficult and can be done with just a few simple steps.

In this article, we’ll guide you through the process of checking your contactor on your AC unit. We’ll cover what a contactor is, why it’s important to check it regularly, and what signs to look for if you suspect that there may be an issue with yours.

Additionally, we’ll walk you through the steps you need to take to safely inspect and test your contactor so that you can quickly get your AC unit back up and running.

So, let’s get started!

Types Of Contactor And Their Use

There are two main types of contactors used in AC units: single pole and double pole. Single pole contactors are typically used for smaller AC units with lower voltage requirements, while double pole contactors are used for larger units that require higher voltage.

The purpose of the contactor is to allow the flow of electricity from the main power source to the compressor and fan motor.

Understanding the different types of contactors and their uses is important when it comes to checking the contactor on an AC unit.

By knowing which type of contactor your unit has, you can ensure that you are performing the correct maintenance procedures and making any necessary repairs or replacements.

Now, let’s move onto identifying the contactor on an AC unit.

Identifying The Contactor On An Ac Unit

After understanding the different types of contactors and their use, it is important to identify the contactor on your AC unit.

The contactor is a small rectangular box located inside the electrical compartment of the unit.

It has two large power cables that connect it to the compressor and one or more smaller control wires that connect to the thermostat.

To identify the contactor, first turn off the power to your AC unit.

Then open the electrical compartment of your AC unit by removing its cover.

Look for a rectangular box with power cables connected to it.

This should be your contactor.

Make sure you take a picture or label all wires before disconnecting any of them.

Now that you have successfully identified your contactor, it’s time to test it. Testing the contactor involves using a multimeter to check if there is continuity between its terminals when there should be and if there isn’t when there shouldn’t be.

This test will help you determine if your contactor needs replacing or if there are other issues with your AC unit that need addressing.

Testing The Contactor

Now that you have located the contactor in your AC unit, it is time to test it. A faulty contactor can cause various problems such as the unit not turning on or off, or failing to cool your home.

Testing the contactor requires a few simple steps and some basic tools.

To test the contactor, first turn off power to the unit at the breaker box.

Then, remove the access panel on the condenser unit and locate the contactor.

Next, use a multimeter to check for continuity between the line side and load side terminals of the contactor.

If there is no continuity, this indicates a faulty contactor and it will need to be replaced.

Use a multimeter to check for continuity.

Line side.

Load side.

If you have determined that your contactor is faulty and needs to be replaced, troubleshooting can help identify root causes of malfunctioning that may affect future replacements. Troubleshooting a faulty contactor involves checking for common issues such as loose connections or damaged wires.

It is important to address these issues before installing a new contactor to prevent further damage or failure. With proper testing and troubleshooting techniques, you can ensure optimal performance from your AC unit and keep your home cool during hot summer months.

Troubleshooting A Faulty Contactor

So, you suspect that the contactor on your AC unit might be faulty. Don’t worry, it’s a common issue that can be easily diagnosed and repaired.

Here’s how to troubleshoot a faulty contactor.

Firstly, switch off the power supply to your AC unit before attempting any inspection.

Once done, locate the contactor- it is a black box with wires running into it.

Check for signs of wear or damage such as melted plastic or burnt wires.

You may also notice pitting on the contact points which indicates arcing due to a high electrical current passing through them.

If any of these signs are present, then it’s time to replace the contactor.

If not, use a multi-meter to test for continuity across the contacts when power is applied.

If there’s no continuity or if voltage isn’t flowing through both sets of contacts, then the contactor needs replacing.

Next, check for loose connections in the wiring leading up to the contactor and see if they need tightening or cleaning up.

It could also be worth inspecting other components such as capacitors or fuses while you have access to them.

Once all checks are done and repairs made (if necessary), switch on power and test your AC unit by turning it on and checking if it is working correctly. Remember to schedule routine maintenance checks every six months so that issues like this can be caught early on and avoid expensive repairs in the long run!


In conclusion, checking the contactor on your AC unit is an important part of maintaining your cooling system.

By understanding the different types of contactors and their use, you can more easily identify the contactor on your specific unit.

Testing the contactor is a simple process that can be done with a multimeter, and troubleshooting a faulty contactor can save you money in the long run.

If you suspect that your AC unit is not functioning properly, it may be due to a faulty contactor.

By following these steps to check and test the contactor, you can quickly identify any issues and address them before they become bigger problems.

This will help ensure that your AC unit continues to function efficiently and effectively throughout the hot summer months.

Overall, taking the time to check and maintain your AC unit’s components can save you time and money in repairs down the line.

Knowing how to identify, test, and troubleshoot a faulty contactor is just one way to keep your cooling system running smoothly all season long.

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