Guide
Why does my AC smell, and what makes it stop?
Almost always the drainage tray: standing water, in the dark, at 30 degrees. It is the one part of the system designed to stay wet, and the one nobody opens.
A smell that arrives with the cooling and fades when the unit is off is coming from inside the unit, not from the room. Here is how to tell which of the four usual causes you have.
The short answer
Four causes, and you can narrow it down in a minute.
A sour or musty smell that starts a few seconds after the AC does is the drainage tray or the coil. A burning smell is electrical and is the one to switch off for. A smell only in one room is that room’s duct or diffuser. A smell everywhere, all summer, is the system.
Nothing you spray into a vent reaches the tray. Air fresheners and duct sprays sit on the first surface they touch, which is the grille — the water they are covering for is a metre further in.
See what an inspection findsThe drainage tray
- ·Condensate that never fully drains
- ·Warm, dark, and wet all summer
- ·The commonest cause by a distance
The evaporator coil
- ·Dust bonds to a wet fin and stays
- ·Smell strongest in the first minute
- ·Cleaned as part of a deep clean
One room only
- ·That room’s branch duct or diffuser
- ·Often a dead insect or building dust
- ·Found by opening that vent, not all of them
Burning or electrical
- ·Switch the unit off at the breaker
- ·This is not a cleaning problem
- ·A technician should look the same day
What actually stops it
Opening the parts that hold water.
The tray comes out, the coil is washed rather than wiped, and the duct behind the grille is cleaned back rather than at the face. Then it is photographed, so you can see the thing that was causing it.
If the smell returns within weeks, the cause was not the one that was treated — which is why the report names what was found rather than what was done.
Book an inspection on WhatsAppCommon questions
Asked about AC smells.
Is a smell dangerous?
We are not doctors and will not tell you what any smell does to anyone’s health. A burning or electrical smell is different: switch the unit off at the breaker and have someone look at it the same day.
Why is it worse when the AC first starts?
Air moves across a wet surface that has been still. Whatever is on that surface arrives in the room in the first minute, then thins out.
Will a duct spray fix it?
It reaches the grille. The water is further in. If a spray worked, the smell would not come back the following week.
How long does the work take?
A one-bedroom apartment is usually three to four hours. A villa depends on the number of units and is confirmed when we quote. Cleaning the drainage tray is part of Deep Clean+.
