Troubleshooting and Fixing Mini Split Clicking Noise: A Comprehensive Guide

The clicking noise in a mini split system can be a common and frustrating issue, often caused by the expansion and contraction of internal plastic components due to temperature changes. While this noise may not be a cause for concern, it can be quite loud and disruptive, especially if it’s keeping you up at night. In this comprehensive guide, we’ll dive deep into the technical details of mini split clicking noise, providing you with a step-by-step playbook to diagnose and address the problem effectively.

Understanding the Causes of Mini Split Clicking Noise

The primary cause of the clicking noise in a mini split system is the expansion and contraction of the internal plastic components, such as the refrigerant lines, valves, and other moving parts. As the temperature in the system fluctuates, these plastic components expand and contract, leading to the characteristic clicking sound.

This phenomenon is particularly common in mini split systems because they often have a large temperature differential between the indoor and outdoor units. The outdoor unit, which houses the compressor and other heat-generating components, can experience significant temperature changes throughout the day, leading to the expansion and contraction of the internal plastic parts.

Additionally, the clicking noise can also be caused by the operation of the reversing valve, which is responsible for switching the system between heating and cooling modes. As the reversing valve switches, it can produce a clicking sound that may be audible.

Diagnosing the Clicking Noise

mini split clicking noiseImage source: Flickr

Before attempting to fix the clicking noise, it’s essential to properly diagnose the issue. Here’s a step-by-step guide to help you identify the root cause of the problem:

  1. Observe the Timing of the Clicking Noise: Pay attention to when the clicking noise occurs. Is it more prevalent during the heating or cooling cycle? Does it happen more frequently when the system is first turned on or after it’s been running for a while? This information can help you pinpoint the specific component or mechanism causing the noise.

  2. Inspect the Indoor and Outdoor Units: Carefully examine both the indoor and outdoor units for any visible signs of damage or wear and tear. Look for cracks, loose connections, or any other physical issues that could be contributing to the clicking noise.

  3. Listen Closely to the Noise: Try to identify the exact location of the clicking sound. Is it coming from the indoor unit, the outdoor unit, or somewhere in between? This information can help you narrow down the potential source of the problem.

  4. Check the Refrigerant Lines: Ensure that the refrigerant lines connecting the indoor and outdoor units are properly insulated and secured. Any loose or exposed lines can cause the clicking noise due to vibration and movement.

  5. Monitor the System’s Operation: Pay attention to the system’s performance, such as airflow, temperature, and humidity levels. Any abnormalities in the system’s operation may be contributing to the clicking noise.

Addressing the Clicking Noise

Once you’ve identified the potential cause of the clicking noise, you can try the following steps to address the problem:

Lubricate the Plastic Components

One of the most common solutions for reducing the clicking noise is to lubricate the internal plastic components. You can use a silicone-based lubricant spray specifically designed for HVAC systems. Follow these steps:

  1. Turn off the mini split system and disconnect it from the power source.
  2. Locate the plastic components, such as the refrigerant lines, valves, and any other moving parts.
  3. Spray the lubricant directly onto the plastic components, ensuring even coverage.
  4. Allow the lubricant to dry completely before turning the system back on.

Secure the Refrigerant Lines

If the clicking noise is coming from the refrigerant lines, ensure that they are properly secured and insulated. Here’s how you can do it:

  1. Inspect the refrigerant lines for any loose connections or exposed sections.
  2. Use insulation sleeves or wraps to cover the refrigerant lines, especially where they pass through walls or other tight spaces.
  3. Secure the refrigerant lines using clamps or brackets to prevent them from moving and causing the clicking noise.

Replace the Reversing Valve

If the clicking noise is related to the operation of the reversing valve, you may need to replace the valve. This is a more complex repair that should be performed by a licensed HVAC technician. They will:

  1. Safely recover the refrigerant from the system.
  2. Disconnect the reversing valve and replace it with a new one.
  3. Recharge the system with the appropriate refrigerant and perform a leak test.
  4. Test the system’s operation to ensure the clicking noise has been resolved.

Replace the Mini Split System

If the clicking noise persists despite your efforts to lubricate the plastic components and secure the refrigerant lines, it may be necessary to replace the entire mini split system. This is especially true if the system is older or has been subjected to significant wear and tear.

When choosing a new mini split system, it’s recommended to avoid homeowner brands like Pioneer, as they may not be as durable or long-lasting as more reputable brands. Instead, opt for well-known and trusted manufacturers in the HVAC industry, such as Mitsubishi, Daikin, or Fujitsu.


The clicking noise in a mini split system can be a frustrating issue, but with the right approach, you can effectively diagnose and address the problem. By understanding the causes, following the step-by-step troubleshooting guide, and considering the appropriate solutions, you can restore the quiet and comfortable operation of your mini split system.

Remember, if the clicking noise persists or you’re unsure about the best course of action, it’s always recommended to consult with a licensed HVAC technician who can provide professional guidance and ensure the safe and proper repair of your mini split system.