New aircon never cooled: line never vacuumed before charging

A brand-new unit had never cooled the bedroom to the set temperature, and two weeks after installation the room still sat several degrees above target. The installer said new units need time to settle in. A correctly set up aircon should cool from day one.

By Team Snowflake | Updated 28 Jul 2026

Case summary

Daikin Wall-mountedunder 3 years oldHDBTampines, Singapore

Concern: The earlier advice was that weak cooling from a new unit was normal and that it just needed time to settle in.
Found: The line was never fully vacuumed before the initial charge, leaving trapped air and moisture that cut cooling capacity even with a correct amount of gas in the system
Key check: Added gas to the correct amount for the pipe run and watched cooling barely improve, which pointed to trapped air and moisture rather than a simple shortfall
Result: The bedroom reached the set temperature for the first time since installation. The recorded readings give a clear basis to raise the skipped evacuation step with the original installer.

What we were told

The unit was installed two weeks ago and has never cooled the bedroom properly. The room still felt warm even after the aircon ran for hours. The installer came back once and said new units need time to reach full performance.

What we checked

A brand-new unit that never reaches its set temperature has a short list of likely causes. The unit leaves the factory tested, so the compressor, coil, and board are unlikely to be at fault. That points back to how the line was prepared and charged. We measured the gas pressure first, then tested how the system responded to a proper charge before assuming a simple shortfall.

Gas pressure readings did not fit the simple pattern of a system that was just short on charge.
A leak check on every pipe joint and service port found nothing, so gas had not escaped after installation.
Adding gas up to the correct amount for the pipe run barely changed how the unit cooled.
Airflow, filter, and coil were all normal, which ruled out a blockage or mechanical fault.

What we found

The refrigerant line had never been vacuumed out before the initial charge. Trapped air and moisture left inside take up space the refrigerant should fill and interfere with how the system carries heat, so the unit still under-performs even once the charge amount looks correct. No leak was found at any connection, ruling out gas escaping after installation. Adding gas to the right level for the pipe run only helped a little, the signature of trapped air and moisture rather than a plain shortfall. That skipped step at installation is why cooling was never right.

What fixed it

We recovered the existing gas, pulled a full vacuum on the line to clear out the trapped air and moisture, and recharged it fresh to the correct level for the installed pipe length. Once recharged, we ran the unit and checked it again. The air at the vent came out clearly colder than before, and colder than the earlier top-up had managed. We recorded the before and after readings so the homeowner could take them to the original installer.

Outcome

The bedroom reached the set temperature for the first time since installation. The recorded readings give a clear basis to raise the skipped evacuation step with the original installer.

What this case teaches us

A new aircon should cool on the first day, not after settling in

There is no break-in period for cooling. If a new unit never reaches its set temperature, the installation is the place to look first.
Weak cooling from day one does not always mean too little gas. If the line was never fully vacuumed before charging, trapped air and moisture can hold cooling back even at the correct charge amount.
Ask whether the line was vacuumed before charging, and for before and after readings in writing. They show whether the full charging process was followed, not just whether gas was added.

Questions this case answers

New aircon not cooling properly: does it need time to settle in?

No. There is no break-in period for cooling, and a correctly set up unit reaches its set temperature from the first day. This Tampines bedroom never got there. Pressure readings did not fit a simple undercharge, a leak check across every joint and port found nothing, and topping the charge to the correct amount barely changed anything.

What does vacuuming the pipes before charging actually do?

It pulls the air and moisture out of the line so only refrigerant remains. Skip it and that trapped air takes up space the refrigerant should fill and interferes with how the system carries heat, so cooling stays weak even when the charge amount reads correct. That skipped step is why this unit had never cooled properly.

Aircon cools weakly from day one: is more gas the answer?

Adding more refrigerant is not the answer when it barely moves the result, and that response is itself the diagnosis. Here the gas was recovered, a full vacuum was pulled on the line, and the system was recharged fresh to the correct level for the installed pipe length. The air at the vent came out clearly colder afterwards.

What should I ask for in writing after an installation?

Confirmation that the line was vacuumed before charging, plus before and after readings. Those show the whole charging process was followed rather than gas simply being added. Readings were recorded on this job for exactly that reason, so there is documented evidence of how the system behaved before the work and after it.

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