What actually happens during an aircon chemical wash or general service

Booking “a service” without knowing what is actually involved makes it hard to tell whether you got what you paid for. General servicing and a chemical wash look similar from the outside, a technician with a toolbox and a ladder, but the process and the result are different enough to matter.

If you are choosing between providers, aircon repair and servicing specialists on this directory are ranked using real customer feedback, which is worth checking before booking. The home page has the full list of categories if you are still working out what kind of visit you actually need.

General service, step by step

A general service is the lighter of the two options and usually follows this sequence:

1. Filter removal and cleaning. The technician pulls the air filters, rinses or vacuums them, and lets them dry before refitting.
2. Visible coil and vent wipe-down. Dust on the accessible surfaces of the indoor unit is cleaned, without opening the casing.
3. Drain check. The condensate drain is checked for blockages, since a clogged drain is a common cause of water leaking from the indoor unit.
4. Gas pressure check. The technician checks refrigerant pressure to confirm the unit is not running low, which affects cooling performance.
5. Outdoor unit check. A quick visual check of the condenser, fan, and surrounding area for debris or obstruction.

Chemical wash, step by step

A chemical wash goes further into the unit and typically involves:

1. Casing removed. The indoor unit’s front casing is taken off to access the coil directly, rather than just the visible surfaces.
2. Coil cleaning solution applied. A cleaning chemical is sprayed onto the evaporator coil to break down grime, mould, and bacteria buildup that a wipe-down cannot reach.
3. Rinse and drain flush. The coil is rinsed and the drain line flushed to clear out the loosened dirt, which also prevents a new blockage.
4. Outdoor unit wash. The condenser coil outside often gets the same treatment, since dust and debris build up there too, especially near roadside or ground-floor installations.
5. Reassembly and test run. The casing goes back on and the unit runs for a period to confirm cooling and check for leaks around the reassembled panel.

Comparing the two side by side

	General service	Chemical wash
Casing opened	No	Yes
Coil cleaned directly	No, wiped only	Yes, chemical clean
Typical time per unit	20 to 30 minutes	45 to 90 minutes
Best for	Regular upkeep, every 3 to 4 months	Deeper clean, every 6 to 12 months or when musty smells appear

Signs it was done properly

A properly done chemical wash should leave the unit noticeably quieter, since a lot of the fan noise from a dirty unit comes from airflow resistance across a grimy coil. Cooling should feel faster, and any musty smell when the unit first switches on should be gone or much reduced. If the same problem, like a musty smell or weak cooling, comes right back within a few weeks, that points to something beyond a routine clean, such as a refrigerant issue or mould growing further inside the ductwork. Ongoing mould buildup between visits can also affect indoor air quality beyond just smell; the health risks of a dirty aircon guide covers what that buildup means for allergies and breathing.

Booking the right one

If your unit has never been chemically washed, or it has been over a year, that is usually the better choice even if it costs more than a general service. If you are on a regular three to four month servicing routine already, a general service between chemical washes is normally enough to keep things running well. Ask the technician which one they recommend after they have actually looked at the unit, since a quick visual check can often tell them more than a description over the phone.

Setting expectations for a multi-unit visit

Homes with several split units rarely get the exact same treatment for each one. A unit above a stove, near a bathroom, or close to a roadside window tends to collect grime faster than one in a quiet, closed bedroom, and a technician working through the house may recommend a chemical wash for the dirtiest units and a general service for the rest on the same visit. This is a reasonable way to keep costs down without skipping the units that genuinely need the deeper clean. Ask for a per-unit breakdown on the invoice so it is clear which service each unit received, rather than one lump total for the whole visit.

Reasonable and fair pricing are among the most consistently mentioned praise points in customer feedback across this directory, which is worth keeping in mind if a quote for a mixed visit comes back higher than expected. Asking which units are getting which treatment, and why, usually clears up the difference quickly.

Details on how this directory ranks providers, including how service-quality feedback is weighted, are on the methodology page.