Why is my aircon cooling unevenly?
One corner of your flat stays warm while the rest cools fine. Three different faults produce that same warm patch, so the pattern matters more than the patch itself. The first thing to settle: does the imbalance shift when you change the louvre angle, or not?
By Team Snowflake | Reviewed 30 May 2026
1. Airflow direction or obstruction
You feel a cold corridor of air where the vent points, and the rest of the room barely changes. The indoor unit discharges from a fixed outlet, so when the louvre is angled toward one side or furniture blocks the stream, cold air concentrates there. The unit is delivering rated output. It is just not reaching the warm areas.
How to tell
This path follows the air direction. Unlike output loss, supply air at the vent stays cold. Unlike a fouled blower, the warm patch moves when the louvre angle or obstruction changes. The system is making cold air; it is aimed poorly.
- One area feels cool within minutes.
- Another area stays warm the whole cycle.
- The warm patch moves when you change airflow direction.
How we confirm it
We test airflow reach across the room by adjusting louvre angle and fan speed, then confirm whether the imbalance disappears with direction changes alone.
Do not retrofit a second indoor unit before the louvre angle and room obstructions are tested. Room geometry is often the only thing reshaping the airflow pattern.
2. Stuck louvre or fouled blower
You aim the vane straight at the warm corner and nothing changes. The louvre motor that should sweep the vane has stuck at one angle, or the blower wheel is caked with dust so some fins move less air than others. Either way the discharge is uneven across the width of the vent, and the warm patch stays put no matter where you point it.
How to tell
This path stays put even when you aim the vane. Unlike a simple direction fault, the warm zone does not move with louvre changes. Unlike output loss, the vent air is still cold. The issue is spread across the outlet, not cooling capacity.
- Uneven feel persists after you change the angle.
- Airflow feels irregular across the width of the vent.
- The vane does not sweep, or sweeps only part way.
How we confirm it
We inspect the louvre motor swing range and blower wheel condition, and measure airflow velocity at the outlet. If movement is restricted or the wheel is fouled, we restore or replace the faulty part.
Do not lower the set temperature to overcompensate. That cools the strong zone harder while leaving the distribution fault active, and raises the chance of icing at the outlet.
3. Overall cooling output drop
The area under the unit cools first and the far wall stays warm, and over the weeks that warm zone has been growing. When system output falls below rated level, the unit cannot push cold air far enough to reach the whole room. The supply air at the vent itself is no longer as cold as it was, so distance from the outlet decides what gets cooled.
How to tell
This path grows over weeks. Unlike direction faults, louvre changes do not restore the far side. Unlike distribution faults, the vent air itself feels less cold. The cool zone shrinks because the system is losing output, not because air is aimed poorly.
- The room takes noticeably longer to cool than it did earlier.
- The cool zone shrinks toward the unit over weeks.
- The unit runs constantly but never reaches setpoint.
How we confirm it
We measure supply air temperature and refrigerant pressure. That shows whether the system has a capacity shortfall. If pressure is low, we trace the leak before discussing a top-up.
Avoid a second unit or gas top-up before supply temperature, airflow, and system capacity are checked.
Related reading
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