How to Test a Relay: Tools, Tips, and Troubleshooting

Quick Summary

• Understanding how relays work, and how to test them to make sure they are working correctly.
• Tips to keep in mind when testing relays.
• The best ways to troubleshoot relays to make sure you properly detect the problem.

Relays are an important part of many different electrical and electronic systems. They function as switches that help you control circuits and are commonly found in technology like cars, household electronics, and industrial equipment.

Knowing how to test a relay is essential in ensuring the system is working as intended and has no faults. This article will examine relay testing in detail and point out some common troubleshooting methods to help you understand how it works.

What Is a Relay and How Does It Work?

Before looking at relay testing procedures, it’s first important to understand how relays work. A standard relay includes an electromagnet, an armature, a return spring, and electrical contacts. When current flows through the coil, it creates a magnetic field that moves the armature, either opening or closing the contacts to control another circuit.

The 3 most common types of relays are:

• Electromechanical Relays (EMRs)
• Solid State Relays (SSRs)
• Reed Relays

Using a Multimeter to Diagnose Relay Issues

The multimeter is one of the best tools to use when testing a relay, as it is very easy to use and pretty reliable. When looking at the question of how to test a relay with a multimeter, there are 2 ways in which the multimeter can be used.

Testing Resistance

The first is to use the multimeter to test the relay’s resistance. You can do this by simply connecting the multimeter’s leads to the relay’s coil terminals. If the relay works properly, the multimeter should show a value between 40 and 120 ohms. It’s important to note that you must set the range meter before performing this test for a manual multimeter. You can set the range to the minimum amount.

Testing for Continuity

The second way is to test for continuity in the relay. To perform this test, you will need to test the continuity between the common(COM) terminal and the normally closed(NC) terminal and the continuity between the COM terminal and the normally open(NO) terminal.

Both of these tests are pretty simple. All you need to do is connect the multimeter’s leads to the 2 terminals you are testing and see if the multimeter buzzes. Buzzing will mean that the relay is working fine and has no problems. If either of the connections doesn’t buzz, then there could be a problem with your relay.

Alternative Ways of Testing Relays

While multimeters are great at testing relays, they are not the only instruments you can use.

Voltmeters

A more basic tool than the multimeter, the voltmeter can also test relays to ensure they work correctly. Testing with the voltmeter works the same as the multimeter, helping you diagnose faulty relays.

Dedicated Relay Testers

You can also get yourself a relay tester to make your life even easier. These relay testers are very simple to use and are specifically designed to test if relays are working properly. So if you are someone who hates relay testing procedures and electrical component testing, make sure you get your hands on a relay tester.

Testing Solid State Relays (SSRs)

You can apply the input test or the output test to test SSRs. For the input test you will simply apply a voltage to the relay and see if the output side responds appropriately. For the output test, you will check either the voltage through the voltmeter or check for continuity.

Tips for Relay Testing

Here are some tips you should keep in mind when testing your relays:

1. Apply the correct voltage: You should always make sure the voltage you are applying to your relay is appropriate as providing higher voltage can cause even more harm to your relay.
2. Label wires: It’s a good idea to label the wires you use as it makes your life much easier.
3. Perform multiple tests: Sometimes performing more than one test is the best approach as the first test might not catch an error or there might be some human error involved.
4. Keep records of what you record: Records can come in handy down the line as you can compare the results of multiple tests to each other. Any discrepancy can then tell you if there might be an error in the relay.

Troubleshooting Relays

To fix a problem, it’s crucial that you are able to detect the problem. For relays, knowing how to properly troubleshoot will allow you to better recognize what the problem might be and what you might need to test. Different relays require different forms of tests. If you are working with a relay in a car, you will need to know how to test a car relay and if you are working with a starter relay you will need to know how to test a starter relay.

With all that said, here are different ways in which you can troubleshoot your relays:

No Clicking Sound When Powered:

• Check the coil resistance with a multimeter.
• Confirm your power supply is delivering the correct voltage.
• Look for mechanical faults or burn marks.

Switching Doesn’t Occur:

• The internal contacts might be worn or broken.
• Ensure the coil is receiving sufficient voltage.

Unreliable or Intermittent Operation:

• This could be due to environmental factors like heat or vibration.
• Try testing under similar operating conditions.

Relay Is Stuck:

• Internal contacts may have fused together.
• The moving parts could be obstructed.

Damaged or Burned Contacts:

• This often results from frequent high-current switching.
• Replace the relay if contact damage is visible.

Preventing Future Issues

The best approach to dealing with relay issues is to prevent the issues themselves. Obviously it is virtually impossible to ensure that there is no error at all, but you can do your best to limit the chance of an error coming up in a relay.

One of the most impactful ways in which you can do this is by regularly testing your relays and performing steps to check if your relay is functioning properly. Routine maintenance will prevent errors from going undetected, and this will make sure they don’t make things worse for you down the line.

Components like flyback diodes and snubbers can also help keep your relays free from problems. You also want to regularly replace old parts or parts that might not be working as they used to when they were first installed in the relay.

Conclusion

So there you have it, an in-depth guide on what you need to do to properly test relays. Knowing how to test a relay is a very valuable skill for anyone who deals with relays on the regular. This guide helps you out by providing very easy ways to test relays, making your life much easier.

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