The compressor is the heart of your HVAC system, and any malfunction in it can disrupt your entire setup. In such cases, having a multimeter at hand can be a real lifesaver. But is using a multimeter to test a compressor really mysterious? The truth is, it is a relatively simple task, provided you know how to do it accurately. In this article, we are going to take you through a step-by-step guide on how to test a compressor with a multimeter and effectively troubleshoot any compressor issues that may arise. So buckle up and let’s get started!

1. Understanding the importance of testing a compressor with a multimeter

Testing a compressor with a multimeter is an essential step in maintaining the functionality of your HVAC system. A compressor is the heart of an air conditioning or refrigeration unit, responsible for compressing the refrigerant vapor to high temperatures and pressures. Without a functioning compressor, the entire system would fail to operate correctly, leading to warm and uncomfortable indoor temperatures or spoiled food in the case of refrigeration. Thus, regular testing of the compressor using a multimeter is critical to identifying issues early and preventing costly repairs or replacements.

A multimeter is an electronic device that measures voltage, current, and resistance and is commonly used in HVAC systems to test electrical components such as compressors. By measuring the electrical values of a compressor, a multimeter will help you determine its operational status and identify potential issues. For instance, if the multimeter reading shows no continuity, this could indicate a failed compressor motor or an open circuit.

Testing a compressor with a multimeter may seem daunting, especially for beginners. However, it is relatively easy and straightforward, provided you have the right tools and follow the correct steps. Neglecting to test your compressor could lead to a more significant issue that could be expensive to fix in the long run. Therefore, it is essential to understand the importance of testing your compressor and investing in a reliable multimeter to perform routine tests. The next section outlines the tools necessary for testing your compressor with a multimeter.

2. Gathering necessary tools before beginning the testing process

Before starting the testing process, it is important to gather all the necessary tools to ensure an accurate and efficient test. Here are the tools that are required to test a compressor with a multimeter:

1. Multimeter: The first and the most important tool you would need is a multimeter. It measures voltage, current, and resistance, making it ideal for testing the compressor. If you do not own one, you can purchase one from your local hardware store or online. It is essential to choose a multimeter that gives accurate readings for voltage and resistance.

2. Safety Gear: It is critical to wear safety gear like gloves and goggles when testing a compressor. This protects your hands and eyes from possible injury. A compressor can generate high-pressure gas that can harm you in case of a leak or explosion. Therefore, make sure to wear appropriate safety gear.

3. Screwdriver: A screwdriver is required to access the compressor terminals. You need to unscrew the cover plate to expose the terminals. Ensure that you have a screwdriver that fits the screws on the compressor.

4. Wiring Diagram: A wiring diagram provides information on how the electrical components of the system are connected. The wiring diagram helps you identify the compressor terminals and determine the right sequence of testing.


Gathering all the necessary tools before starting the testing process is essential to ensure an accurate diagnosis of the compressor. It is also crucial to wear the appropriate safety gear to protect yourself from possible harm from high-pressure gas. In the next section, we will provide a step-by-step guide to testing a compressor with a multimeter.

3. Step-by-step guide to testing a compressor with a multimeter


Testing a compressor with a multimeter is a quick and straightforward process that can help you identify if there are any electrical issues with the compressor. Before testing, it is essential to follow proper safety protocols and turn off all power sources to the HVAC system. Here is a :

Step 1: Check for voltage

The first step is to ensure that you have power going to the unit. Use a voltmeter to verify if you are getting the appropriate voltage at the unit’s electrical connections. If there is no power input, the compressor will not turn on, and there is no need to continue the testing process.

Step 2: Set the multimeter to Ohms

Set the multimeter to Ohms and ensure that you are working on the proper scale to test the compressor’s resistance. You can usually identify the appropriate scale by referring to the owner’s manual or by checking the compressor’s labels.

Step 3: Test the compressor’s resistance

Connect the multimeter leads to the compressor’s terminals and check the readings. A healthy compressor will typically show a low resistance reading between 3 and 4 Ohms. If you get no reading, your multimeter’s batteries may be weak, or there may be an issue with your probes or wiring connections.

Step 4: Check for ground potential

If you get a high resistance or an infinite reading, there may be a ground potential issue with the compressor’s windings, indicating that the compressor is grounded. Test this by connecting one meter lead to a compressor terminal and the other to an unpainted metal spot on the compressor’s body. If you get a zero reading or a low resistance reading, there is a grounding issue.

Testing a compressor with a multimeter is a great way to identify any electrical issues before they turn into more significant problems. If you encounter any readings or issues that you do not understand or are beyond your expertise, call a professional technician to diagnose and repair the issue.

4. Interpreting multimeter readings and diagnosing potential issues

Once you have successfully tested your compressor with a multimeter, the next step is to interpret the readings to identify any potential issues. It is important to note that multimeter readings should always be compared against manufacturer specifications to determine whether your compressor is operating at optimal performance. Here’s a step-by-step guide to .

1. Inspect the Multimeter Readings

Before interpreting the multimeter readings, it is important to take note of the three readings obtained from the tests – ohms, amps, and volts. Each of these readings provides valuable information that helps identify potential issues with the compressor. A high or low reading may signify an underlying problem with the compressor, such as a faulty motor or a leak in the refrigerant line.

2. Compare the Multimeter Readings with Manufacturer Specifications

Once you have inspected the multimeter readings, compare each reading with the manufacturer’s specifications. If the readings are within the acceptable range specified by the manufacturer, the compressor is operating normally. However, if any of the readings fall outside the manufacturer’s recommended range, this may indicate a potential issue with the compressor.

3. Diagnosing Potential Issues

If the multimeter readings indicate a potential issue with the compressor, it is important to identify the root cause of the problem. For instance, if the ohms reading is higher than the manufacturer’s recommended range, it may indicate a problem with the compressor motor. On the other hand, if the amps reading is below the recommended range, it may signify that the compressor is not working efficiently.

To diagnose potential issues with the compressor, it is important to consult with a professional HVAC technician. They will have the necessary expertise to diagnose the issue accurately and provide recommendations for repairs or replacements.

By following these steps, you can identify potential issues with your compressor and take appropriate steps to ensure that it operates efficiently. Remember, regular maintenance and inspections can prolong the lifespan of your compressor and save you money on costly repairs or replacements in the long run.

5. Troubleshooting common problems encountered during compressor testing


When testing a compressor with a multimeter, there are several common problems you may encounter. These issues can cause inaccurate readings or even damage to the compressor if not handled properly. In this section, we will discuss some of these common problems and how to troubleshoot them.

1. Open Circuit

An open circuit is one of the most common problems that can occur during compressor testing. This happens when the electrical connection between the compressor terminals and the multimeter is broken. To troubleshoot this issue, start by checking the connections between the multimeter and the compressor terminals. Make sure that the wires are securely attached and that there is no damage to the wires or terminals.

2. Short Circuit

Short circuits occur when there is a direct connection between the compressor terminals. This can cause damage to the compressor and may lead to inaccurate readings on the multimeter. To troubleshoot this issue, start by checking the wiring between the compressor terminals. Make sure that the wires are not touching each other and there are no cuts or breaks in the insulation.

3. Faulty Multimeter

A faulty multimeter can also cause issues during compressor testing. This can lead to inaccurate readings or no readings at all. To troubleshoot this problem, start by checking the battery. Replace the battery if it is low or dead. If the battery is not the issue, try using a different multimeter to see if the problem is with the device itself.

By troubleshooting these common problems, you can ensure that your compressor testing is accurate and safe. Remember to always take the necessary precautions when working around electrical equipment and follow the manufacturer’s instructions and guidelines.

6. Best practices for maintaining and prolonging the lifespan of a compressor

Maintaining and prolonging the lifespan of a compressor is crucial for the efficiency and longevity of your HVAC system. Here are some best practices to consider:

Regular maintenance

Regular maintenance of your HVAC system, including your compressor, can greatly extend its lifespan and help prevent costly repairs. This includes cleaning or replacing air filters, checking for proper refrigerant levels, lubricating moving parts, and inspecting electrical connections. It is recommended to schedule a professional maintenance check at least once a year to catch any potential issues early on.

Avoid overworking the compressor

Overworking the compressor can cause it to wear out more quickly, leading to more frequent repairs and a shorter lifespan. To avoid overworking the compressor, make sure your HVAC system is properly sized for your home or building, and avoid setting the thermostat too low or too high. It is also recommended to use a programmable thermostat to adjust the temperature automatically based on your schedule.

Keep the compressor clean and clear

Dirt, dust, and debris can accumulate on the compressor over time, obstructing airflow and causing it to work harder than necessary. Regularly cleaning the compressor and keeping the area around it clear can help improve its efficiency and prolong its lifespan. It is important to turn off the system before cleaning and to use caution when handling any electrical components.

By following these best practices, you can help ensure the longevity and efficiency of your compressor and HVAC system.

7. Tips for choosing the right multimeter and ensuring accurate readings

One of the essential tools for testing a compressor is a multimeter, which measures the electrical properties of the system. Choosing the right multimeter is crucial to getting accurate readings and diagnosing potential problems. Here are a few tips to help you select the right multimeter and ensure accurate readings.

1. Consider the type of multimeter

There are two main types of multimeters: analog and digital. Analog multimeters have a needle that moves across a scale, while digital multimeters display readings on a digital screen. Digital multimeters are more accurate and easier to read, making them a better choice for compressor testing.

2. Look for essential features

When choosing a multimeter for compressor testing, look for essential features like voltage, resistance, and continuity. Make sure it has a voltage range of at least 600V, a resistance range of 200 ohms to 2 megaohms, and a continuity buzzer.

3. Check for accuracy

Most multimeters are calibrated at the factory, but it’s crucial to ensure accuracy before using them. Use a calibration standard or a known source to check the multimeter’s accuracy.

4. Consider safety features

Compressor testing involves working with electrical systems, so safety features are crucial. Look for a multimeter with features like overload protection, short-circuit protection, and automatic shutoff.

5. Read reviews and ratings

Before purchasing a multimeter, read reviews and ratings from other users to learn about their experiences with the product. Look for features they found helpful or any reliability or accuracy issues they experienced.

6. Proper usage

To get accurate readings with a multimeter, use it correctly. Follow the manufacturer’s instructions and take precautions like grounding the system before testing to avoid accidents.

By following these tips, you can choose the right multimeter and ensure accurate readings for compressor testing. A high-quality and accurate multimeter can help diagnose potential problems and keep your HVAC system running smoothly.

People Also Ask

Can you test a compressor with a multimeter?

Yes, a multimeter can be used to test a compressor’s resistance and continuity. This will help determine if there are any wiring or electrical issues within the compressor that may be causing it to malfunction.

What should the reading be on a compressor with a multimeter?

The readings on a compressor with a multimeter will vary depending on the make and model of the compressor. It is important to consult the manufacturer’s specifications to determine the proper readings for your specific compressor.

What are the symptoms of a bad compressor?

A bad compressor may display symptoms such as not cooling properly, making unusual noises, or failing to turn on at all. If you suspect that your compressor is not functioning properly, it is important to have it tested and serviced as soon as possible to prevent further damage.

What is the difference between a continuity and resistance test?

A continuity test determines if there is a continuous electrical path in a circuit, while a resistance test measures the resistance of the circuit to the flow of electricity. Both tests can be performed using a multimeter and can help diagnose issues within an electrical system, including a compressor.

How can a multimeter help diagnose compressor issues?

A multimeter can help diagnose compressor issues by measuring the resistance and continuity of the compressor’s electrical components. This can help identify issues with the wiring or electrical connections that may be causing the compressor to malfunction.


In conclusion, a multimeter can be an invaluable tool for diagnosing issues with a compressor. By measuring resistance and continuity, a multimeter can help identify issues with the compressor’s electrical components that may be causing it to malfunction. If you suspect that your compressor is not functioning properly, it is important to have it tested and serviced as soon as possible to prevent further damage.