New block outdoor unit rattles: packing block left behind
A new Tengah flat had an outdoor unit that rattled whenever wind funnelled through the gap between two blocks. The unit was under two years old, so a mechanical fault seemed unlikely. On a fresh install, leftover packing from transport is often the simplest explanation for a rattle like this.
By Team Snowflake | Updated 28 Jul 2026
Case summary
Mitsubishi Electric Wall-mounted2 years oldHDBTengah, Singapore
- Concern
- A unit less than two years old already seemed to have a genuine fan or motor fault.
- Found
- A shipping packing block used to protect the fan during transport and installation had been left inside the unit and was rattling against the fan guard
- Key check
- Checked inside the fan guard for leftover installation packing before assuming a fan blade or motor fault
- Result
- The rattle stopped completely as soon as the packing block was removed, at every fan speed the unit ran at. The homeowner avoided paying for fan work on a unit that never actually needed it in the first place.
What we were told
The rattle started as soon as the unit was installed and happens every time it runs, though it is most noticeable on the fan's higher speed setting. The unit still cooled normally throughout. It had been installed under two years earlier at handover.
What we checked
A rattle present since day one was the first lead. That mattered more than opening the fan motor on a unit this new. A fan or motor fault usually develops gradually as parts wear. A noise present from the very first run points instead at something left behind during installation.
The fan motor ran smoothly and evenly with no unusual sound when tested on its own.
A block of shipping foam, meant to hold the fan still during transport, had been left inside the guard after installation.
The foam knocked lightly against the guard every time the fan spun, loudest whenever the unit ran at a higher speed.
The fan blade itself showed no damage, warping, or imbalance anywhere along its edge.
What we found
New outdoor units ship with foam or plastic blocks wedged in place to stop the fan from shifting during transport. Installers are supposed to remove every one of these before handover. This block sat tucked behind the guard, easy to miss during a quick final check. Once the unit was running, normal fan vibration was enough to knock the loose foam against the guard. The sound came back every time the unit switched on.
What fixed it
We removed the leftover packing block and checked the rest of the guard and housing closely for any other pieces left behind from transport. We did not recommend any fan or motor work, since both tested cleanly once the block was out. We advised asking for a final packing check on any new install, since this kind of leftover piece is easy for an installer to miss.
Outcome
The rattle stopped completely as soon as the packing block was removed, at every fan speed the unit ran at. The homeowner avoided paying for fan work on a unit that never actually needed it in the first place.
What this case teaches us
A rattle on a brand-new unit often means leftover packing, not a loose part
- A rattle present from the very first run usually means something was left behind during installation, not a developing fault.
- New installs are worth a quick check for leftover shipping packing, foam blocks, or plastic ties around the fan and guard.
- Ask whether the fan guard and housing were checked for leftover shipping packing before approving any fan or motor work.
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?
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Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.