Why Is My Freezer Making a Humming Noise?

Have you ever noticed your freezer making a humming noise? The sounds are soft enough that you hardly hear them, but when you do, you may be concerned about whether it’s a good thing or a bad thing.

Freezers make a humming noise because of their compressor, which comprises a pump and motor that push refrigerant through a vapor compression cycle. This cycle uses the second law of thermodynamics to keep freezers cold. However, if your freezer is making abnormally loud sounds, call a professional.

The humming noise your freezer makes is perfectly normal for the most part. It’s usually a sign that the freezer’s components are working. Read on to know more about how freezers work and some of the reasons your freezer makes abnormal sounds.

How Your Freezer Makes Its Humming Noise

In his YouTube video, “What’s Inside a Refrigerator Compressor,” Sixtyfiveford cuts open the compressor’s welded casing to reveal the two components: the motor and the pump. These parts are responsible for that soft humming sound. 

The compressor doesn’t stay on all the time. Freezers contain a thermostat that monitors the internal temperature and switches the compressor off when it’s cold enough to keep food items cold. The thermostat keeps freezers energy-efficient.

What’s the Purpose of the Compressor?

The purpose of the compressor is to convert low-pressure vapor into high-pressure vapor. When switched on, the pump feeds low-pressure vapor into the chamber, and a motor turns the piston, which compresses vapor made from the refrigerant.

When the piston pressurizes the vapor, it pushes it through a tiny hole with a small piece of aluminum on the other side to keep it from depressurizing.

How Freezers Work

The vapor that comes out of the condenser is hot, so it turns into a liquid via a condenser. The condenser is a winding trail of metal piping found on the back of your freezer. By dispersing the heat outside the unit, the condenser cools the pressurized vapor into a liquid.

Newer units might have a compact condenser situated at the bottom of the unit. Compact condensers use a fan to cool down the vapor. This arrangement pushes the hot air outside using a vent. 

The vapor continues through the throttling device, which drops the pressure and temperature.

After that, the liquid travels up to the evaporator, which sits inside your freezer.

Per the second law of thermodynamics, heat always moves from a warmer object to a colder object. So, the evaporator cools your freezer by drawing any warmth towards it and away from your food.

When the refrigerant evaporates completely, it’s fed right back to the compressor so it can be reused.

This handy Youtube video describes the entire process:

Reasons Your Freezer May Be Overly Loud

The compressor is mounted on springs and rubber feet which minimize friction, so your freezer shouldn’t make too much noise. Specifically, you shouldn’t be able to hear your unit’s normal humming noises if you’re outside the kitchen or nowhere near your fridge.

But if your freezer constantly makes loud sounds like clicking, clunking, knocking, or scraping, consider enlisting professional help, especially if you notice a decrease in freezer temperature. There are many possible causes for a freezer breaking down, so it’s best to let a trained technician handle the problem.

That said, here are some possible issues your freezer may experience that can cause loud noises:

Compressor Is Overheating

Your freezer may not be working because the pump piece in your compressor has melted. Since these pieces are made of plastic, they may begin to melt if your compressor is overheating. When this happens, you can lose the functionality of the pump, and the melted plastic can clog up the motor’s piston so it can’t compress the gas.

There’s also a fair bit of lacing that keeps the wire coils in the motor from slipping. If your compressor overheats, that lacing could tear, and you’ll end up with a bunch of loose wires sitting in oil.

Ice Buildup

The air that circulates your freezer has moisture in it, so there’s a chance your freezer could suffer from ice buildup. That isn’t good for your food because it could suffer from freezer burn, and it’s not great for the mechanical components either.

The ice generally forms around the evaporator coils, the vent, and on the walls of your freezer. If you notice excessive buildup, it might be time for a thaw. Most freezers have a defrost cycle, so refer to your user manual to figure out how to turn it on.

However, thawing can cause your drip pan to overflow, so make sure to monitor the defrosting process. If you don’t clear your drip pan, you might find water damage or mold the next time you take a closer look at your appliance.

Full or Loose Drip Pan

A full drip pan is generally a good sign because it means your unit is working. However, if you notice water sloshing noises, it’s probably time to empty it. After all, you don’t want to make a mess on the floor if you so much as bump into the pan.

Also, your drip pan may be a source of rattling sounds. If this is the case, a little duct tape can do the trick. Just access the panel using the instructions from your appliance’s manual and stick the tape where the drip pan could use some extra support.

Fan Is Worn or Damaged

An evaporator fan circulates the cool air from the evaporator in a circular motion. This process allows your freezer to have different levels of cold air. If this fan is worn or damaged by dust or ice, you’ll notice a decrease in temperature because the cold air can’t disperse evenly.

Condenser Coils or Vents Are Dusty

If your condenser coils are snuggled in a blanket of dust, the vapor coming out of your compressor won’t be able to cool properly. Likewise, if your air vents are dusty, your unit won’t have adequate airflow, resulting in an overly loud noise.

These things can disrupt the entire refrigeration process, but they can be easily remedied by dusting the area with a Fiada Fin Cleaning Coil Brush (link to Amazon). This brush is specifically designed to clean delicate surfaces without causing damage.

Alternatively, you can carefully vacuum the backside using a brush attachment.

Screws Are Loose

Over time, screws can loosen due to the constant vibration of the compressor. Ensuring that these screws remain tight will decrease any weird noises your freezer may make. You can find these screws at the back of the unit, so check there periodically to lower the risk of odd noises. Your freezer’s user manual should have a diagram showing the location of your screws.

Unit Not Level

Rattling noises can occur if your freezer unit isn’t set on a level surface. If this is the case, you can adjust the feet. Again, refer to your user manual for guidance. You might also hear a rattling noise if the fridge is too close to a wall or other surface. Fix this by shifting your freezer so that there’s at least an inch of space between your unit and the wall.

Final Thoughts

The compressor creates the humming noise coming from your freezer, which has a motor and a pump that circulates the refrigerant through the system. This process is called the vapor compression cycle, which uses the second law of thermodynamics.

Even though your freezer normally makes some noise, you should pay attention to any unusually loud or frequent knocking or scraping. Ensure that your freezer is in good shape by checking that screws are tightened in place and that there’s no dust on the coils or vent. If the temperature in your freezer drops, call a technician to assess the problem.