12/01/2026
Why Doesn’t my Air Conditioner Cool Instantly?
Introduction
We’ve all been there. Coming home on a sweltering Summers day, you immediately reach for the air conditioning controller and turn it on, but, all you feel is warm air. “Why is that” you think to yourself. This doesn’t mean there is anything wrong with your air conditioning system, it’s just turning on. The reason why your air conditioner doesn’t cool instantly is that is needs to expel the hot air from the duct work, or at the front of the air conditioner louvers in the case of a split system, before it can begin cooling. In this blog post, we will explore why this happens and the steps you can take to improve this in the future.
Understanding How an Air Conditioner Cools
How does an air conditioner work in cooling? Well, let us explain. In cooling mode, the air conditioner uses refrigerant to absorb excess heat from the room, and then pumps this absorbed heat through a series of pipes to the coil at the outdoor unit. There are a number of components that make up an air conditioner (regardless as to whether it is a reverse cycle ducted or a split system). Let’s explore a few of those components below:
Refrigerant
Refrigerant is a type of liquid or gas that moves through the air conditioner, carrying with it the heat absorbed from a room. The refrigerant then travels outside, where its released. In heating mode, the flow is reversed as the air conditioner absorbs heat from outside and transfers this inside.
The Compressor
A compressor pressurises the refrigerant so it can move around through a series of copper pipes that connect the indoor unit to the outdoor unit.
The Reversing Valve
The reversing valve is the little switch in your air conditioner that tells the air conditioner whether it is heating or cooling the home. This is done by reversing the flow of refrigerant and therefore reversing the flow of heat transfer.
The Inverter
An inverter acts like a speed controller for your air conditioner, allowing the system to ramp up and down as demand (temperature) changes inside the home. Inverter technology is found in almost every modern air conditioner and is one of the main reasons why modern air conditioners are so much more efficient than older models.
Why Isn’t Cooling Instant?
When you first turn the air conditioner on, especially if it’s late in the afternoon after your house as absorbed all the heat from outside, your air conditioner is frantically working to start cooling. The whole system needs a moment to turn on; the indoor unit needs to cycle on; it needs to increase the fan speed to meet the user input (set temperature point) and then work to expel any hot air inside the duct work. That is why, especially for zoned reverse cycle ducted systems, you may feel warm air from the outlets for a period of time even when the air conditioner is set to cooling. The compressor also needs time to circulate the refrigerant through the system, and then it can begin absorbing the heat in the rooms.
When Was The Last Time You Cleaned Your Filter?
Having a dusty, dirty or clogged filter will only make your air conditioner work harder. When the filter is clogged and dusty, the air conditioner is working even harder to filter the air as it reaches the indoor unit. That’s why Ford & Doonan recommend cleaning or replacing the filter once every 6 to 12 months, and as frequently as every 3 months if you have pets or are particularly prone to allergies. Click the buttons below to watch our DIY YouTube videos.
Operating Modes
Modern smart controllers, like the AirTouch range, are far more intuitive than even some manufacturer controllers. With clear 7” and 8” colour touchscreens, switching between modes is far easier as the whole display changes colour together (blue for cooling, orange for heating and green for dry mode).
Unfortunately, some controllers aren’t quite as initiative as they ought to be. If you air conditioner still isn’t cooling and if no cool air is coming from the vents after more than 30 minutes of operation, double check you have it set to cooling. Cooling mode is often displayed as a snowflake icon, whereas heating mode is often the sun icon. Other modes may be AUTO mode, fan only mode or dry mode. AUTO mode is where you chose the temperature, and the air conditioner decides whether it needs to heat or cool to reach that set point. Fan only mode circulate room temperature air, without heating or cooling it. Dry mode is a form of dehumidification.
Ambient Temperature
The ambient temperature places a very big part if the effectiveness of cooling your house down in summer. Letting the house absorb all the heat from the day, and then only turning the air conditioner on at 5PM when you get home on a 38°C day is the most inefficient way of cooling your home. Instead, Ford & Doonan recommend setting a timer so the air conditioner turns on between 1-3 hours before you’re due home. That way, the air conditioner has a chance to absorb the heat that’s built up so far, and prepare a nice cool home for your arrival. On modern controllers, this can be done via the mobile app for iOS/Android. For older controllers, it may need to be set before you leave via the settings on the wall controller.
So, How Long Should it Take to Cool a Room?
As there are many factors at play, there is no single ‘rule’ for how long it should take to cool a room down. A large living room, for example, with multiple floor to ceiling windows facing in a Westerly direction will take far longer to cool than a small South facing bedroom. The best thing you can do is keep the curtains drawn if it will be a particularly warm day, start the air conditioner before you arrive home, and ensure the filters are cleaned or replaced regularly. Another step you can take is investing in further window treatments, such as UV reflective window tinting or external window shades to keep the sun from hitting the glass.
How To Help your Air Conditioning Cool Faster
Lets summarise a few points we’ve outlined in this blog post so far:
Start Early
Set the air conditioning to come on between 1-3 hours before you arrive home, ideally just before or just after the day has reached its maximum temperature. That way you’re greeted by cool air instead of warm air.
Close Doors, Windows and Blinds
Refrigerated air conditioning works differently to evaporative air conditioning. Refrigerated air conditioners don’t need outside air, meaning closing all external windows and doors is essential in summer. Whereas, evaporative air conditioners do rely on outside air to work effectively. Whilst I’m sure its very nice looking out the window on a sunny day, all you’re doing is letting all that heat inside the room, meaning you’ll be waiting longer until its cool!
Clean your Air Conditioner Filter
Regular cleaning or replacing of the filter in your split system or ducted air conditioner is a very easy DIY tasks to improve the efficiency and effectiveness of your air conditioner. Ford & Doonan recommend this at least once every 6 to 12 months, but can be a frequently as once every 3 months for those will allergies or pets. Scroll up this blog post for links to you DIY YouTube videos.
Conclusion
Whilst there is no one single ‘rule’ for how long it should take to cool a room down, if you find yourself asking why doesn’t my air conditioner cool instantly? Be sure to use the timer function to cool the house down before you arrive home, close your curtains and blinds and take 5 minutes out of your weekend to clean or replace your air conditioner filters. If you’d like to book a service, or enquire about a new air conditioner, click one of the buttons below.
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