If your AC cools well for the first 30–60 minutes then cooling performance drops, the most common cause is low refrigerant gas or an overheating compressor.
Data Verified: 2026Low gas causes a characteristic pattern: the AC cools initially when some refrigerant is available, but as the cycle continues, the insufficient gas can no longer maintain the cooling load. You will notice the room temperature slowly rising after the first hour despite the AC running.
Overheating compressor is the second cause. If the outdoor unit's condenser coil is dirty or airflow is blocked, the compressor overheats after sustained running and activates thermal protection — reducing or stopping cooling. Clean the outdoor unit and ensure 30cm clearance on all sides.
Dirty indoor filter can also cause progressive cooling reduction — as the coil ices up from restricted airflow, cooling drops over time. Check if ice is forming on the indoor unit copper pipe.
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Why does my AC work fine at first but stop cooling after an hour?
Classic low gas symptom. The limited refrigerant handles initial cooling but cannot sustain it. Also check for outdoor unit overheating from blocked airflow.
Is ice on the indoor unit normal?
No. Ice on the indoor unit copper pipes indicates either very low gas or severely restricted airflow (dirty filter). Turn off the AC, let ice melt, fix the cause, then restart.
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