How to Test Refrigerator Start Relay with a Multimeter

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Do you notice your refrigerator warming up too fast? Does it generate a ticking sound? Maybe your unit is not cooling the food, but it sounds like it’s running. If all of these sounds familiar to you, it’s more likely your refrigerator start relay might be bad.

In case you didn’t know yet, a refrigerator start relay is a component typically attached to the compressor to jumpstart the compressor. 

The compressor of your fridge doesn’t work throughout the day. You see, it goes on and off throughout the cooling cycle to keep its optimum temperatures inside the fridge. The relay is a component supplying your appliance with power. Hence, the compression can’t function without the relay itself. 

Keep in mind that the compressor will not start if the relay malfunctions, not to mention you may need to bypass the relay system. If you prefer to do that, you also need to bypass the thermal overload. That could be extremely risky. 

What if you leave the relay bypass on for a longer time? Expect that it will cause a bypass overload overheating your appliance, and other systems will decay and wear out from too much overheating.

Remember that a relay bypass is not a permanent solution. It will help if you get your relay fixed right away by a skilled electrician. 

How Does a Start Relay Functions? What Is Its Role? 

A refrigerator start relay is an electronic switch that ignites the compressor, a device producing the cold air running through your fridge to keep all your foods cool. 

It increases the compressor by governing when it must turn on or off based on the refrigerator’s need for cool oil.

You see, the start relay helps you save energy, avoids overheating, and guarantees your unit functions appropriately. 

Therefore, how does it work? A start relay switches on the compressor when the thermostat in the fridge notices a high internal temperature. However, the thermostat can’t deal with the compressor’s current. That’s why it switches on the relay.

Then, the relay turns on the compressor by using power with the overload device to the compressor motor’s secondary winding. It then provides you an additional force to start working. 

How Can You Tell If a Start Relay in Your Unit is Faulty? 

As you can notice, the compressor plays an integral role in your unit. However, it requires a functional and efficient start relay. 

Below are the common indications to help you understand if your relay system is in good working condition or just faulty. 

Sign #1. There’s a rattling sound

Try to do a shake and rattle test on your refrigerator. To do this, do a physical check on the relay to understand if it’s working or not. 

Unplug your unit from the main power source. Open the panel at the back of your unit to find the relay on the compressor. Remove the start relay and shake it. 

Do you notice a rattling sound inside the relay? That could indicate there’s something loose inside and requires replacement. 

If you didn’t find any rattling sound, then the problem could be with the compressor itself. If you prefer, you can also check for burn marks around the relay ports to figure out if it blew. 

Sign #2. There’s a click sound

You will normally find an audible click whenever the relay starts the compressor. The click is always there whether the compressor turns on or not. 

However, if the compressor does not turn on, the refrigerator start relay will try to start it shortly after. That occurs in intervals of 2-5 minutes. Hence, it suggests the start relay is malfunctioning if that clicking sound happens recurrently. 

Sign #3. Your unit is not cooling

Take note that an inefficient cooling system is the most obvious indication of a faulty or malfunctioning start relay. A functional fridge normally creates a humming sound throughout the day. That implies a working compressor.

However, if the compressor is not cooling your fridge, it means the relay is bad. 

How to Test Your Start Relay? 

One of the best tools you can utilize to test your refrigerator start relay is a digital multimeter. A multimeter is an electronic device that measures current, voltage, and resistance. It accurately shows the measured values as numerical values on the LCD. 

You can use it to perform a variety of current tests. Even low-cost measuring instruments for hobby purposes measure the standard values of ohmic resistance, electrical current, and electrical voltage. That’s possible in direct current circuits (DC) and alternating current (AC). Bear in mind that high quality and current professional multimeters have added features and continue to measure:

  • sound 
  • continuity
  • electrical capacity
  • diodes
  • transistors
  • inductance of components
  • temperature
  • frequency of the flowing current
  • air humidity 

For your wire-wound relays, it can be checked using a digital multimeter. You will find three terminals on the relays—two marked M and S and a slip-on terminal labeled K. 

  1. Place the two probes of the multimeter on the two terminals, M and S. The reading must be zero. 
  2. Flip the relay over with your probe still touching the terminals. A click sound must be heard, and the multimeter ought to read infinity or O.L.
  3. Perform the same steps, but with the probes touching the terminals L and S. In this case, the reading must be zero even if it’s flipped over.
  4. If not, change the relay with a new one. Ensure you buy the same relay type from your supply store.

Troubleshooting and testing your refrigerator start relay will optimistically show the main issue. 

Final Thoughts

Just make sure that you pay attention to the signs of a malfunctioning start relay to prevent overheating the unit and overconsumption of power. With this article, you will be able to test your refrigerator start relay without any troubles. 

Nonetheless, we don’t suggest leaving your unit on testing mode for too long. Consider booking an appointment with a professional electrician or technician to repair the relay properly.

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