Many consumers have reported significant noise issues with their Mitsubishi Mr Slim air conditioning systems, particularly with the outdoor units. These problems appear to affect many recent models and have been ongoing for several years. In my own experience, I bought a new Mitsubishi reverse cycle system for about AUD $13000, only to find that the system was so noisy that I did not want to turn it on. Mitsubishi did replace the outdoor unit. I am happy to report that the new unit is much better, much quieter. If you have a noisy unit - contact Mitsubishi and ask them to take a look.
⚠️ Mitsubishi Mr Slim Air Conditioner Noise Problems:
Mitsubishi air conditioning units. producing a very loud buzzing sound.. The buzzing comes from the compressor. If you're considering purchasing a Mitsubishi system or experiencing noise problems with your current unit, this information is intended for you.
Table of Contents
Excessively Noisy Mitsubishi split systems (heat pumps). Including Mr Slim models.
Common Noise Complaints Include:
- Loud buzzing or humming from outdoor units
- High-pitched whining that penetrates through walls
Type of Noise Issue Reported
1. Outdoor Unit Buzzing and Humming
The most commonly reported issue is a persistent buzzing or humming sound from the outdoor unit (specifically the compressor) that is significantly louder than expected. Users describe it as a "brain drilling buzz" that penetrates through ambient noise and can be heard indoors - even through double brick walls, disrupting sleep, work and daily activities.
Real User Experiences and Complaints
Community Discussion Links:
Reddit Discussion: What is that annoying buzzing on my Mr Slim 18KW outdoor unit (M180LAAV)
Reddit Discussion: Very loud Mitsubishi external aircon unit
Reddit - Noisy compressor Solved: Explains how a noisy compressor was fixed by flushing and repressurizing the system
Geekzone Forum: Mitsubishi Mr Slim noise complaints
Product Review: Ok unit, bit noisy when ramping up PEA-M140HAA (14kW)
Whirlpool: MXZ-3E54VAD-A1 outdoor unit is loud when ramping up and down
Reddit - High Pitched Whine complaint: MXZ-SM42NAMHZ outdoor unit - High pitched noise discussion
Facebook - Noisy compressor - 16W, Single Phase: Refrences suggest compressor running max
User Report 1: Sleep Disruption
"We haven't slept in two nights. Our repair guy is stumped. When we switched to heat as it got cold, the indoor wall unit started making a clicking/cracking noise whenever the compressor kicked in... Fast forward to now. We have started needing the unit for cooling at night.... and there goes that clicking noise."
User Report 2: Neighbor Complaints
"How the actual F Mitsubishi can sell this for residential use is insane. That buzzing noise would do my head in – so droney and penetrative! We get -6 in Canberra. Nice quiet residential areas. Silence, and my Mitsubishi unit sounding like that LMFAO."
User Report 3: Warranty Issues
"We had a similar problem on several Mitsubishi indoor units a year or so after they were installed. They fixed it by replacing a sleeve bearing on the squirrel cage fan under warranty. Now another year later the same bedroom unit that had a bearing replaced is making the same intermittent ticking sound."
User Report 4:
Model: PUZ-ZM125VKA2-A
Install date: 2025-04-17
"3 days after having my 12.5kw Mr Slim unit installed it started making a very loud high pitched whining noise at the compressor end when ramping up on heater mode. Contacted supplier and installer who did nothing about it. Contacted local Mitsubishi agent who came and looked at it.
He found that the suction pipe inside tha unit was vibrating against the cover and visible wear could be seen on the pipework. He bent the pipework away from the cover, which reduced the noise but did not eliminate it. My neighbour has a Mr slim 17kw unit and it makes no noise at all. The agent se
nt me a bill for $130 saying it wasn't a warranty issue. I disagree. Unit had been in for 6 weeks and it's supposed to have a 5 yr warranty.
I would not recommend anyone buy a mitsubishi unit. Don't honour their warranty and it's obviously a production issue."
Audio Evidence of Noise Problems
🔊 Watch and listen to Real User-Submitted Videos
The following videos were submitted by users experiencing noise issues with their Mitsubishi Mr Slim, Ecodan and Hyper Heat systems:
Video 1: Outdoor Unit Buzzing (PUZ-ZM100VKA2-A, 10KW)
Source: PUZ-ZM Model
This recording demonstrates the typical buzzing/humming noise that many users report from their outdoor units.
Video 2: Mr Slim Operational Noise (PEA-M140HAA, 14KW)
Source: Loud Mr Slim outdoor unit
This video shows the noise levels during normal operation that Mitsubishi Techs have said is unacceptable but Mitsubishi said is normal
Video 3: Mitsubishi Outdoor unit
Source: Loud Mr Slim Outdoor Unit
This video shows a noisy Mitsubishi Outdoor unit (looks like a Mr Slim also)
Video 4: Ecodan Outdoor unit (11.2 KW)
Source: Noisy Ecodan unit before and after getting fixed
This video shows a noisy Ecodan outdoor unit. The noise shows the compressor noisier than it should be. Then the video shows the noise level after the compressor is fixed.
Video 5: Hyper Heat Outdoor unit (SUZ-KA36NAHZ)
Source: Noisy Hyper heat outdoor unit
This video shows a noisy Hyper heat outdoor unit. The noise shows the compressor noisier than it should be. Shows internal parts. There are several comments on this
video that indicate this is typical of Mitsubishi units. There is ref to (PUZ-SM100KVA) experiencing the same buzzing noise.Video 6: Smart Multi Outdoor unit
Source: Noisy Smart Multi outdoor unit
This video shows a Smart Multi heat outdoor unit. The noise shows the compressor noisier than it should be. User says it was fixed by draining the Freon from the entire system and re-loaded and pressurized to spec .
Share Your Mitsubishi Mr Slim Noise Experience
📤 Help Others by Sharing Your Audio/Video Evidence
If you're experiencing similar noise issues with your Mitsubishi Mr Slim system, please share your audio or video files to help document this problem. Your submission could help other consumers make informed decisions.
Potential Solutions and Workarounds
What Users Have Tried:
- Replace Outdoor unit: In our case the, the outdoor unit was faulty and had to be replaced. There was a 4 degree temp offset that had to be turned off also.
- Reducing Power: Mitsubishi acknowledges the loud compressor noise is typical of their units. By setting the maximum power levels, you can reduce the % that the compressor ramps up. This will not remove the noise but it will stop the unit ramping up into the highest level. This is not really a solution but more of an option to run the system in a reduced capacity to remove the most annoying noise.
- Gas Replacement: Draining the Freon Gas and then replacing the gas and pressurizing to spec (Multiple mentions of this as a solution). This solution indicates that some compressors respond to having more gas in the system. This may be influenced by your location (different countries allow different refrigerants). In Australia we use R32 and this will not impact the compressor buzzing noise.
- Insulation: Adding sound-dampening materials around units
Our Assessment and Recommendations
Based on the documented evidence and numerous user reports, it appears that noise issues with Mitsubishi systems can occur. In our case, Mitsubishi conducted extensive readings of the unit while it was in operation. After analyzing the data, they determined that a replacement was necessary. The new unit is approximately 30% quieter, delivers improved performance, adjusts its output as needed, and consumes less power compared to the previous unit.
What System is quiet - What should I buy?:
This article is not selling anything. After Mitsubishi attended our house and replaced the outdoor unit, I can recommend a Mitsubishi.
⚠️ Before Purchasing a Mitsubishi Split System:
- Listen to operating units in person Ask friends, family and the vendor for examples and go listen to it. Listen to it ramping up after starting cold.
- Ask about noise specifications and get them in writing
- Consider noise requirements for your specific installation location
- Research alternative brands with better noise performance records
- Ensure strong warranty coverage that specifically addresses noise issues