A practical guide to winterising your air conditioner

Knowing how to winterize your air conditioner for off-season storage is most useful in southern Australia, where winter genuinely interrupts household cooling. Melbourne can be damp and changeable, while Canberra often brings frost and freezing nights. In Brisbane and Perth, warm or humid weather can keep cooling systems working beyond the traditional winter off-season.

Split systems are a leading choice in Australian homes, often with an outdoor compressor mounted on a balcony, wall bracket or side yard. Ducted units, portable air conditioners and window models need different preparation, so the manufacturer’s manual should determine the method rather than a generic checklist.

A good winterising routine limits corrosion, mould, dust ingress and pest damage while keeping next summer’s start-up simple. It can also reveal a blocked drain, loose connection or damaged cord before the unit is needed at full capacity.

Match the routine to your system

Start by identifying the exact model and reading its manual. Note whether the unit is a split system, ducted unit, portable model or window unit, and whether it has a heating function. Some reversible air conditioners need only a light clean because they continue running through winter. Others require complete disconnection, drainage and covering. Keep the manufacturer’s instructions and warranty documents together for reference.

Inspect the unit before storage and photograph its condition. Look for rust, leaking water, damaged insulation, loose panels, unusual noises and blocked vents. Record the installation date and obtain any service history from the original installer. This information makes it easier to separate existing problems from anything discovered after storage.

Choose a suitable time based on local conditions and household habits rather than the first cold day. Many Australian families leave their air conditioner powered for occasional heating during winter, so full shutdown may be unnecessary. Ducted systems should generally remain under the care of an experienced technician, particularly if they include complex controls, drainage pumps or interconnected heating equipment.

Clean the indoor and outdoor parts

Switch off and isolate the power before cleaning. Remove the indoor filters according to the manual, then wash or vacuum them as directed and allow them to dry completely. A blocked filter restricts airflow and encourages dust and mould around the evaporator. Replace a damaged filter rather than attempting to repair fine mesh or electronic components.

The outdoor condenser also needs attention. Use a soft brush to remove leaves, lint and cobwebs from the coil and casing, then rinse the coil gently if the manufacturer permits it. Avoid high-pressure water, which can bend delicate fins or force moisture into electrical parts. Keep water away from power connections, and never clean an energised unit.

Clear the condensate drain and pan so water cannot stagnate inside the cabinet. Follow the manual’s flushing method and use only a manufacturer-approved cleaning product where one is specified. For broader moisture-control advice, the guidance on reducing indoor humidity can help address dampness that remains after the air conditioner is switched off.

Dry, isolate and protect the unit

Many households turn the unit off with the remote but leave it connected to power. For true storage, switch the controller to off, isolate the unit at its wall isolator and unplug it only if the plug and socket are accessible and dry. Allow any remaining moisture to evaporate before covering the indoor unit. Do not use an extension cord or modify the original plug arrangement.

Do not open the refrigerant circuit or attempt to drain compressor oil yourself. Australia’s used-refrigerant framework and its state and territory implementation require refrigerant to be handled by appropriately licensed refrigeration technicians. Refrigerant must be recovered for recycling or disposal rather than vented. Electrical work on fixed wiring is also governed by state and territory rules, so use a licensed electrician where disconnection is required.

Fit a purpose-made, weather-resistant cover over the outdoor compressor if the manual recommends one. Secure it against Melbourne’s sudden winds without blocking ventilation, and avoid an airtight plastic sheet that can trap condensation. Keep the unit upright, and never place it on its side unless the manufacturer expressly allows this. Do not allow children, pets or stored objects to obstruct service panels.

Store it for Australian conditions

Outdoor units are usually best left in their installed position. Coastal Sydney can bring salt-laden damp air, while Melbourne’s winter condensation can settle into vents and metal surfaces. Canberra’s frost and Perth’s fine summer dust create different concerns, and Brisbane’s humid conditions can prolong moisture-related corrosion. Use a ventilated cover, maintain clearance around the casing and inspect drainage paths during long storage.

Portable and window units can usually be stored indoors if the manual permits. Empty the tank and drain hoses, clean the filters and coils, and let every part dry thoroughly. Keep the unit upright in a stable, ventilated space away from direct sunlight, heaters, paint fumes and strong chemicals. A breathable cover or original carton is preferable to sealed plastic.

During storage, check the unit every few weeks for water, insects, leaves and corrosion. Keeping the drain path clear and performing a monthly visual inspection can prevent HVAC breakdowns when the cooling season begins. Before reconnecting a stored unit, remove the cover, clean the filters, restore power at the isolator and test both fan and cooling modes. Stop and obtain service if it leaks, smells burnt or fails to operate normally.

Make a safe, practical storage plan

The appropriate level of involvement depends on the system, its installation and its condition. Routine cleaning and covering suit many owner-installed split systems, while fixed wiring, refrigerant work and ducted controls call for professional assistance.

System type	Sensible owner preparation	When professional help is needed	Storage goal
Split system	Clean filters and coils, clear drainage, isolate power and fit a breathable cover	Relocation, leakage, refrigerant work, fixed wiring or uncertain controls	Upright, dry, sealed and ventilated
Ducted or reversible system	Limited exterior cleaning where the manual allows	System shutdown, pump inspection, controls, refrigerant and integrated heating equipment	Correct winter mode or a technician-led shutdown
Portable or window unit	Empty, clean, dry and cover before taking indoors	Electrical faults, damaged components or difficult drainage	Dry indoor storage in an upright position

Use a professional when the unit is hardwired, has a refrigerant line issue, has recently been installed or has an unfamiliar control system. Compare experienced HVAC pros, request a written scope of work and keep the invoice with the service records. Prepare the air conditioner now, book any required service before the first hot weekend and keep it clean, dry and ready for the next cooling season.