How to Test an AC Relay With Multimeter: An HVAC Repair Guide

If you're having trouble with your AC, the first thing you should do is test the relay. This article will teach you how to test an AC relay with multimeter in a few easy steps. But before jumping on testing you must have a clear understanding of how a relay works and what does it do in your AC.

How a Relay works?

A Relay is basically an electrically operated switch. It is used to control a circuit by opening and closing it using an electromagnet. The electromagnet only requires a small amount of current to operate, but it can control both high power circuit and lower power circuit depending upon coil terminals.

When the relay is turned on, the electromagnet becomes activated and closes the switch, allowing current to flow through the circuit. When the relay is turned off, the electromagnet is deactivated and the switch opens, interrupting the current.

What does a Relay do in your AC?

The relay in your AC controls the flow of electricity to the compressor. The compressor is what circulates refrigerant throughout your AC system. When the relay is turned on, the compressor turns on and begins circulating refrigerant. When the relay is turned off, the compressor turns off and stops circulating refrigerant.

Exquisite process temperature control is essential for many industrial applications. Achieving the precise process temperature requires a comprehensive understanding of how to test an AC relay.

How to test an AC relay with Multimeter

The most common type of AC relay is the compressor relay. The compressor relay controls the compressor, which is the heart of the air conditioning system. If the compressor fails, the entire system will fail. That's why it's so important to know how to test an AC relay.

Tools Required to Test An AC Relay

  1. Digital Multimeter

  2. Compressor Relay

  3. Jumper Wire

  4. Additional Single line Switch

  5. An independent voltage source (12V)

How to test an AC relay with Multimeter in 4 Easy Steps?

To test HVAC relay with a multimeter, you must have a clear understanding of the relay schematic sheet. If you don't have a multimeter then you can select from our list of top 10 multimeter for HVAC work. Although most of the compressor relays are of the same type so let's get started.

  1. First, you'll need to identify which of the three terminals on the relay is which. The terminal on the left is known as the "common" terminal, while the one on the right is known as the "normally open" terminal. The one in the middle is known as the " Normally closed" terminal.
  2. Next, you'll need to test the electromagnet. To do this, you'll need a multimeter set to the ohmmeter setting. Touch one lead of the multimeter to the common terminal on the relay, and the other lead to the normally open terminal. The multimeter should read zero ohms. If it doesn't, then there's a problem with the electromagnet.
  3. Now, you'll need to test the switch. To do this, you'll need a multimeter set to the continuity setting. Touch one lead of the multimeter to the common terminal on the relay, and the other lead to the normally closed terminal. The multimeter should beep, indicating that there is continuity between the two terminals. If it doesn't, then there's a problem with the switch.
  4. Finally, you'll need to test the circuit itself. To do this, you'll need a multimeter set to the voltage setting. Touch one lead of the multimeter to the common terminal on the relay, and the other lead to the normally open terminal. The multimeter should read 12v control voltage (in ON position). If it doesn't, then there's a problem with the circuit. I have also made a separate guide on electrical wiring testing.

If you find that there is a problem with the relay, you'll need to replace it. You can find replacement relays at most auto parts stores or on amazon.

How to replace faulty AC Relay?

Testing the relay is a good place to start if you're having trouble with your AC. By following the steps in this article, you'll be able to identify whether or not the relay is working properly. If you find that there is a problem with the relay then by following steps mentioned below you can easily replace it.

  • First, you'll need to find the relay of the same rating and specifications. You can find replacement relays at most auto parts stores or on amazon.

  • Next, you'll need to disconnect the power to the AC unit. The best way to do this is to shut off the breaker that supplies power to the unit.

  • Once the power is disconnected, you'll need to remove/de-soldered the old relay with a soldering iron.

  • Then, you'll need to take the new relay and connect it in place of the old one. Make sure that all the terminals are properly connected/soldered.

  • After that, you'll need to reconnect the power to the AC unit by turning on the breaker.

  • Finally, you'll need to test the AC unit to make sure that it's working properly.

By following the steps above, you should be able to easily replace a faulty AC relay. However, if there is an issue in the logic circuit then ac compressor will not start. You can test low-power logic signals with mV or diode test mode of multimeter.

Safety Guide:

Electricity is dangerous. If you don't know how to safely work with electricity, then you should not attempt to test the relay or replace it. Try to follow following 10 precautions.

  • Shut off the power to the AC unit before you begin working on it. The best way to do this is to shut off the breaker that supplies power to the unit.

  • Wear rubber gloves when handling the relay. Rubber gloves will protect you from electric shock.

  • If you're using soldering iron then try to use one with a built-in thermal protection circuit. This will help to prevent the iron from getting too hot and causing a fire.

  • Do not touch any of the terminals on the relay with your bare hands. Always use tools to make adjustments or connections.

  • Never attempt to bypass the relay by connecting the two terminals together with a wire. This could cause a fire or electric shock.

  • Do not use the relay if it is damaged in any way. Discard it and get a new one.

  • Make sure that all the terminals are properly connected/soldered before you turn on the power to the AC unit.

  • Never leave the soldering iron unattended while it is turned on.

  • Keep the area around the AC unit clean and free of flammable materials.

By following these safety precautions, you can help to prevent accidents while working with electricity. If you have any further questions or concerns about how to test an AC relay with multimeter, then ask for professional help.

Conclusion

Air conditioners are a common appliance in many homes and businesses. They work by circulating cool air through the building to help keep it comfortable during hot weather. The AC unit has a number of different components, one of which is the relay. The relay helps to control the flow of electricity to the AC unit. If the relay is not working properly, it can cause problems with the AC unit.

You can test the relay with a multimeter to see if it is working properly. If you find that there is a problem with the relay, you can replace it with a new one. Always follow safety precautions when working with electricity. If you have any further questions or concerns about how to test an AC relay, get a technician onboard

Please feel free to leave a comment below if you have any questions or suggestions.

Happy Testing!

Frequently Asked Questions:

How to trace a relay switch on an air conditioner?

The best way to find the relay is to consult the air conditioner's wiring diagram. The diagram will show you where the relay is located and how it is connected to the circuit. You can also use a multimeter to trace the circuit. There are also some AC relays that have a built-in indicator light. This can be helpful in finding the relay.

How to test an ac capacitor with a multimeter?

To test an AC capacitor, you will need to use a multimeter set to the "micro-farad" setting. You will need to test the capacitor while it is connected to the circuit. The multimeter will measure the capacitance of the capacitor. If the reading is close to zero or infinity, then the capacitor is defective and needs to be replaced.

How often should I replace my AC filter?

It is generally recommended that you replace your AC filter every three months. However, this may vary depending on the type of filter you have and how often you use your AC unit. You can check your owner's manual for specific recommendations.

What happened if you replace a faulty relay with a good one on an air conditioner?

If you replace a bad relay with a good one, it should fix the problem. However, if the problem was caused by something else, such as a faulty compressor, then replacing the relay will not solve the issue. Always consult your owner's manual or a professional technician to diagnose and repair your AC unit.

Solid state relay requires no regular maintenance, how often should I check them?

Solid state relays do not require regular maintenance. However, you should check them periodically to make sure they are working properly. You can use a multimeter to test the relay.

What is an AC clutch relay?

An AC clutch relay is a device that helps to control the flow of electricity to the AC unit. If the relay is not working properly, it can cause problems with the AC unit. You can test the air conditioner clutch relay with a multimeter to see if it is working properly.

Leave a Comment