New Block Outdoor Unit Rattles: Packing Block Left Behind
A brand-new unit makes a noise and a warranty conversation begins. Some noises on a new install cost nothing to rule out first.
By Team Snowflake | Updated 24 Aug 2026
How this presents
A knocking from an outdoor unit on a newly completed installation, present since the very first day it ran. It has never once been quiet. Cooling performance is exactly what was expected of it.
- Setup
- Mitsubishi Electric Wall-mountedNew installHDBTengah
- Misread as
- A manufacturing defect on a unit that has only just been installed.
- Check first
- Whether the unit has ever been quiet since the day it was installed
What else produces this
Something that has never worked properly is a handover question rather than a fault, and on brand-new equipment that narrows the field a long way. Nothing has had time to wear, corrode or loosen. What can be wrong on day one is what was done or not done at installation. Packing left inside the casing sits near the top of that list, because removing it is a step with nothing at all to prompt it.
Noise present from the very first run rules out anything that develops with age or use.
Normal cooling performance confirms the equipment itself is working as designed.
A transit block still fitted inside the outdoor casing accounts for the knocking on its own.
An absence of wear or damage across the whole installation confirms it is otherwise entirely sound.
Why it happens
Manufacturers fit blocks and ties inside a unit so its moving parts cannot be damaged in transit. Those are meant to be taken out during installation, and the instruction sits in a manual that is very often left unopened. Once the covers go back on there is nothing to see. The unit then runs, the restrained part moves against the block, and a brand-new machine makes a noise it should never have been capable of making.
What resolution involves
The transit protection is removed and the unit runs quietly from then on. It is worth asking about directly on any new installation, since it costs nothing and the alternative is a warranty conversation about a machine that was never faulty. A checklist item is all this needs, and its absence is why the fault keeps appearing.
How to tell it worked
The unit run through a full start and stop cycle after removal, not simply switched on. Restrained parts sometimes only make contact during starting or stopping, which a steady run will not reveal.
Before you approve a quote
Noise from day one usually came in with the packing
- Transit blocks and ties go inside the machine and are meant to come out at installation.
- Nothing on new equipment has had time to wear. A day-one noise belongs to the handover.
- Ask directly whether transit protection was removed. It costs nothing and settles it immediately.
Questions this case answers
Why has my new aircon rattled since the day it was installed?
What gets left inside outdoor units after installation?
Rattle on a unit under two years old: is a fault developing?
What should be requested at the end of a new install?
Ready to get started?
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.