Compressor Knocking Sound Refrigerator

Introduction

A knocking sound coming from your refrigerator, especially near the back, is usually related to the compressor. The compressor is the heart of your refrigerator, responsible for circulating refrigerant that keeps your food cold. When it starts knocking, it’s a sign something isn’t quite right and needs attention. Ignoring this sound can lead to reduced cooling, spoiled food, and eventually, a complete refrigerator failure. Addressing it early can often save you money and prevent food waste.

Common Causes of compressor knocking sound refrigerator

There are several reasons why your refrigerator compressor might be making a knocking noise:

Loose Mounting Bolts: Over time, the bolts holding the compressor in place can loosen, causing it to vibrate and knock against the frame.
Worn-Out Rubber Dampers: Many compressors sit on rubber dampers to absorb vibrations. These can degrade and crack over time, reducing their effectiveness and leading to knocking.
Internal Component Failure: The compressor itself has internal moving parts. If these parts are damaged or worn, they can cause a knocking sound.
Refrigerant Issues: While less common for a knocking sound specifically, incorrect refrigerant levels or blockages can put extra strain on the compressor, indirectly contributing to noise.
Overload: Running the refrigerator at excessively low temperatures or frequently overloading it with warm food can strain the compressor, leading to knocking.
Dirty Condenser Coils: Dust and debris on the condenser coils can restrict airflow, causing the compressor to work harder and potentially make noise.
Starting Relay Issues: The start relay helps kickstart the compressor. A failing relay can cause the compressor to start roughly, making a knocking sound during startup.
Oil Issues: The compressor needs oil to lubricate its moving parts. Low or contaminated oil can cause increased friction and knocking.

Symptoms Checklist

Here are some signs that can indicate the knocking sound is a compressor issue:

Knocking sound coming from the back of the refrigerator, near the bottom.
The sound is more noticeable when the refrigerator is running.
Cooling performance is diminished (food not staying as cold).
The sound is intermittent it comes and goes.
The refrigerator is vibrating excessively.
The knocking sound is accompanied by other unusual noises like buzzing or clicking.

How to Fix compressor knocking sound refrigerator Step-by-Step Guide

Follow these steps to troubleshoot the knocking sound:

Unplug the Refrigerator: Before doing anything, disconnect the refrigerator from the power outlet. This is crucial for your safety.
Locate the Compressor: The compressor is typically a black, football-shaped component located at the back of the refrigerator, near the bottom.
Inspect Mounting Bolts: Check the bolts that secure the compressor to the frame. Use a wrench to tighten any loose bolts. Be careful not to overtighten, as this could damage the compressor.
Examine Rubber Dampers: Look for the rubber dampers or mounts underneath the compressor. If they are cracked, brittle, or deteriorated, they may need replacing (though we will address this later). Note their condition.
Clean Condenser Coils: The condenser coils are usually located on the back or bottom of the refrigerator. Use a vacuum cleaner with a brush attachment to remove any dust or debris.
Check for Obstructions: Ensure nothing is touching the refrigerator or impeding airflow around it. Make sure the refrigerator is level and not wobbling.
Listen Carefully: Plug the refrigerator back in and listen closely to the compressor. Note exactly when the knocking occurs (e.g., during startup, constantly, etc.).
Monitor Temperature Settings: Make sure your temperature settings are appropriate. Extremely low settings can overwork the compressor. Increase the temperature setting slightly.
Avoid Overloading: Do not overfill the refrigerator, especially with warm items. This forces the compressor to work harder.
Observe for Ice Buildup: Check for excessive ice buildup in the freezer. This can indicate a defrosting problem that is indirectly straining the compressor.
Power Cycle: Unplug the refrigerator for 30 minutes, then plug it back in. This can sometimes reset the compressor and resolve minor issues.
Check the Starting Relay: The start relay is usually a small component mounted on or near the compressor. A visual inspection may reveal burn marks or damage. (Do NOT disassemble unless comfortable with electrical components).

Fix the Issue Without Buying Parts

Before considering replacement parts, try these methods:

Reset: Unplugging the refrigerator for an extended period (30 minutes or more) can sometimes reset the internal electronics and temporarily resolve the issue.
Cleaning: Regularly cleaning the condenser coils and ensuring proper airflow is essential maintenance.
Recalibration: Adjusting the temperature settings to a slightly warmer level can reduce the strain on the compressor.
Inspection Tips: Regularly inspect the mounting bolts and rubber dampers for any signs of wear or loosening.
Maintenance Basics: Avoid overloading the refrigerator and ensure the door seals are airtight to prevent the compressor from overworking.

When Replacement Might Be Necessary

If the knocking persists after trying the above steps, or if the rubber dampers are severely deteriorated, replacement might be necessary. Replacing the compressor itself is a complex task best left to a qualified technician and can cost between $300 and $800 USD, including labor. Commonly failing parts include the rubber dampers (often a relatively inexpensive fix) and the starting relay. A failing compressor is obviously the worst case. Before replacing the compressor itself, get a professional diagnosis.

Safety Warning

Always unplug the refrigerator before attempting any repairs.
Avoid working on electrical components if you are not comfortable with them.
Keep the area around the refrigerator dry to prevent electric shock.
Do not attempt to disassemble the compressor itself.
If unsure, consult a qualified appliance repair technician.

Tools You May Need

Screwdriver (Phillips and flathead)
Wrench set
Vacuum cleaner with brush attachment
Gloves

FAQ

Here are some frequently asked questions about refrigerator compressor knocking:

Q: Is a knocking compressor dangerous? A: While not immediately dangerous, a knocking compressor indicates a problem that can lead to refrigerator failure and potential food spoilage.
Q: Can I ignore the knocking sound? A: It’s best to investigate the knocking sound as soon as possible to prevent further damage and potential food waste.
Q: How long will a knocking compressor last? A: It’s impossible to say for sure. It could fail immediately, or last for months. It’s better to address the issue before it fails completely.
Q: Does turning up the temperature fix the knock? A: Increasing temperature might reduce the strain on the compressor and lessen the sound. But it will not fix the underlying issue.

Conclusion

A knocking compressor can be a worrying sound, but often the issue is relatively minor. By following these troubleshooting steps, you can often identify and resolve the problem yourself, saving time and money. However, if the knocking persists or if you are uncomfortable performing these tasks, don’t hesitate to call a qualified appliance repair technician for assistance.