Foul Odor When Unit Operates

Question

Accepted Answer

Mold and bacteria growth — moisture on evaporator coil and drain pan. Check: Remove indoor unit front panel, visually inspect coil and drain pan — black or green discoloration indicates mold. Use flashlight to check for slime deposits between coil fins. What to do: 1) Apply antibacterial coil cleaner → let stand 30 min → rinse with water. 2) Remove drain pan, clean with 50°C water + neutral detergent. 3) Install antimicrobial pad (silver-ion or photocatalyst type) to prevent recurrence. Annual professional AC cleaning recommended. Burning smell — overheating electrical components (coil, wiring). Check: Stop unit immediately. After power off, visually inspect electrical components — burn marks (brown/black), melted insulation. Measure motor winding resistance (imbalance >10% = faulty). What to do: Never restart with burning smell — electrical fire risk. Identify burned components (motor, PCB, wiring) and replace. Measure insulation resistance between winding and case with 500V megger (≥1MΩ is acceptable). After replacement, re-verify running current is normal. Refrigerant leak odor — sweet chemical smell. Check: Immediately open windows and ventilate. Locate leak source with electronic refrigerant leak detector. Check refrigerant pressure with low-side gauge — lower than normal confirms leak. What to do: Repair leak (re-flare, re-braze) → nitrogen pressure test (1.5 MPa, 24h) → vacuum (below 500μmHg, 30 min) → recharge to specified amount. HFC refrigerants (R-410A, R-32, etc.) must be handled only by licensed technicians.

Foul Odor When Unit Operates

Likely causes

Mold and bacteria growth — moisture on evaporator coil and drain pan

Burning smell — overheating electrical components (coil, wiring)

Refrigerant leak odor — sweet chemical smell

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