The Problem
A family of four living in a double-storey terrace house along Jalan Desa Utama, Desa Petaling, called us about a persistent musty smell coming from all three bedrooms whenever the aircond was switched on. The units — Midea MSMA Series, all 1.0HP — had been running for about four years without any deep cleaning. Regular filter washing was done monthly, but the smell had been getting worse over the past two months.
The homeowner mentioned that his youngest daughter had started developing a mild cough at night, which his paediatrician suspected could be linked to poor indoor air quality from the aircond. He wanted all three units thoroughly cleaned, not just a basic service — he specifically asked for a chemical wash to address the mould and bacteria build-up inside the evaporator coils and blower fans.
Our Assessment
When our Masters Aircond Service KL technician inspected the units, the evaporator coils on all three were heavily caked with dust, mould, and biological growth. The blower wheels (cross-flow fans) were coated in a sticky black residue — a classic sign of years of moisture and dust combining in a humid Malaysian environment. The drain pans also had algae build-up, which was partially blocking the condensate drainage.
We recommended a full chemical wash for all three units. This involves removing the blower wheel, soaking the evaporator coil and components in alkaline-based coil cleaner, and flushing everything with pressurised water. Unlike a basic service that only cleans the surface, a chemical wash reaches deep into the fin gaps of the coil where mould colonies thrive.
Work Timeline
Step 1: Preparation & Protection
Laid protective plastic sheets over the bedroom furniture and flooring. Turned off the electrical supply to each unit at the isolator switch. Removed front panels and air filters.
Step 2: Blower Wheel Removal
Carefully extracted the cross-flow blower wheel from each indoor unit. The blower wheels were soaked in a tray of coil cleaning solution for 20 minutes to dissolve the embedded grime.
Step 3: Evaporator Coil Chemical Treatment
Sprayed the evaporator coils with professional-grade alkaline coil cleaner. Allowed 15 minutes of dwell time for the chemical to break down mould, grease, and biological matter trapped between the aluminium fins.
Step 4: High-Pressure Rinse
Flushed all components with pressurised water using a wash bag to contain the runoff. The water came out dark brown initially, gradually clearing to clean after multiple rinse cycles.
Step 5: Drain Pan & Line Cleaning
Cleared algae from drain pans and flushed the drainage lines with diluted bleach solution to prevent future blockages. Reassembled all components and restored power.
Step 6: Testing & Handover
Ran all three units for 30 minutes. Measured outlet temperature at 10-11°C across all units — a significant improvement from the pre-wash 16-18°C readings. No musty smell detected.
Results
Lessons & Tips
If your aircond has a musty or sour smell that doesn't go away after washing the filters, it's almost certainly mould growing on the evaporator coil and blower wheel. A basic service won't fix this — you need a proper chemical wash. For homes in Desa Petaling and surrounding areas, we recommend a chemical wash every 12–18 months, especially if you have pets or family members with allergies.
Regular filter cleaning is still important between chemical washes. We tell our customers to wash their filters every two weeks during peak usage months. Also consider running the aircond in fan-only mode for 15 minutes after turning off the cooling — this helps dry out the evaporator coil and reduces mould growth. If your units haven't been serviced in over a year, a chemical overhaul may be more appropriate than a wash.
Kevin Chong
Kevin leads the Masters Aircond Service KL team with over 12 years of hands-on experience in residential and commercial aircond systems across Kuala Lumpur. He personally oversees every installation project to ensure quality workmanship.
Aircond Smelling Musty?
Book a professional chemical wash with Masters Aircond Service KL — from RM 120 per unit.
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