Condo not cold traced to dirty evaporator, not compressor fault
Aircon case in Tanjong Pagar, Singapore: cooling loss traced to evaporator coil heavily caked with dust and grime, restricting airflow and heat exchange across the coil surface after targeted diagnosis checks.
Case details
What client reported
The aircon in the master bedroom has not been cold for a few weeks. Another company came and said the compressor was losing capacity and recommended replacing the entire outdoor unit. The condo is in an older high-rise block and the unit has been running for about nine years.
What we found
Before testing the compressor, we opened the indoor unit and inspected the evaporator coil. A nine-year-old unit in a high-rise bedroom can accumulate significant dust if not chemically washed regularly.
- Evaporator coil was heavily caked with a thick layer of dust and grime across the entire surface
- Airflow through the coil was severely restricted — air was bypassing the coil edges instead of passing through
- After chemical wash, the coil surface was fully exposed and airflow returned to normal
- Cooling output dropped to the correct temperature range within minutes of restarting — compressor was running normally
Years of dust and grime had built up on the evaporator coil, forming a thick insulating layer. Air could not pass through the coil properly, and heat exchange was drastically reduced. The compressor was pumping refrigerant normally the entire time — it just had no heat to absorb because the coil surface was blocked.
What we did
A chemical wash of the evaporator coil cleared the buildup and restored full cooling. No compressor work was needed. The client was advised to schedule chemical washes regularly to prevent the same buildup from recurring.
Full cooling was restored after the chemical wash. The compressor and outdoor unit were retained. No parts were replaced.
Timeline
Day 1
Condo aircon not cold — told compressor was failing and unit replacement recommended
Day 1
Inspected evaporator coil condition before condemning the compressor — coil was visibly blocked with buildup
Day 1
Evaporator coil chemically washed — full cooling restored with existing compressor
What we learned
Dirty evaporator vs compressor failure — how to tell the difference.
- A dirty evaporator coil blocks airflow and prevents heat exchange. The refrigerant cannot absorb heat from the room, so the air blows but stays warm. This looks identical to low cooling from a compressor issue.
- A compressor fault shows abnormal pressure readings on the refrigerant circuit. A dirty coil shows normal pressures but poor air temperature drop across the coil. Checking the coil visually before measuring pressures can save time.
- Chemical washing the evaporator coil removes the buildup and restores heat exchange. If cooling returns after the wash, the compressor was never the problem.
Best next step
If your unit is behaving similarly, start with the service path that fits this case before approving broader scope.
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