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The air conditioning troubleshooter.

It's blazing hot (or freezing cold) outside but you are as hot (or cold) inside because the air conditioner won't work properly. Before panicking, run through this guide to see if you can get it running again. I also recommend you bookmark this page, even if you don't need it now, because when you need it you will need it in a hurry. This troubleshooter also covers the operation of your house as a whole. Note that the toubleshooter is of a general nature and some items will not apply to all air conditioners. In particular some items won't apply to cooling only air conditioners and some items won't apply to ducted units while others won't apply to room air conditioners. If in doubt refer to the manufacturers instructions. Make sure you follow your manufacturers safety instructions- if in doubt get professional help.

Which topic most closely describes the problem?

If you can't find an answer here try our Refrigerative Air Conditioning troubleshooting weblog

Fault Possible reasons recommended action
The air conditioner is not running at all and no control lights are on. (If there are no control lights you will need to check the next category as well) Air conditioner not plugged in (if applicable) Plug air conditioner in
Air conditioner not switched on at the wall Switch air conditioner on
Air conditioner not switched on at the control Switch air conditioner on
Circuit breaker has tripped Reset the circuitbreaker at the electrical switchboard
Flat batteries in remote controller Try manually switching on at the unit (and replace batteries)
No power at the power point Plug another electrical device in (eg a radio cassette or similar) and if no power check the circuit breaker.
Refer also to the next section  
Internal fault in the air conditioner Call service
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The air conditioner is not running but some control lights are on Control is in a timer mode Refer to your instruction manual
Control is in heat mode in summer or cool mode in winter Use auto mode (recommended unless there is a specific reason not to use it) or heat in winter and cool in summer
One of the controller functions is waiting for something to happen before starting. The delay could be due to 'defrosting', 'delay after restart', 'delayed fan start on heating' or some other function Wait 10 minutes to see if it restarts itself, if not try resetting the air conditioner
The thermostat not calling for heating and air conditioner has a 'fan off when temperature ok' mode Check the thermostat temperature (refer setting the thermostat)
A safety device (usually high pressure) has tripped out Reset the air conditioner (it may be necessary to wait 20-30 minutes before it will restart)
Internal fault in the air conditioner Call service
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Indoor fan runs but the air coming out is not cool (on cooling) or warm (on heating) Thermostat not calling for cooling or heating Check the thermostat temperature (refer setting the thermostat)
Control is in heat mode in summer or cool mode in winter Use auto mode (recommended unless there is a specific reason not to use it) or heat in winter and cool in summer
Outdoor fan not running Wait 10 minutes to see if it restarts itself, if not try resetting the air conditioner
Outdoor fan running but the air coming out is not much different in temperature to the surrounding air (it should be hotter in summer and colder in winter.) Try resetting the air conditioner
Internal fault in the air conditioner Call service
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Compressor runs excessively and the room is too cold in summer or too hot in winter Thermostat set too high or low Check the thermostat temperature (refer setting the thermostat)
Internal fault in the air conditioner Call service
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Compressor runs excessively but can't bring the room to a comfortable temperature (ie room too hot in summer or too cold in winter) Outdoor temperature is hotter than the temperature the air conditioner was selected for (summer) (or colder in winter) Check your quote to see if a temperature was specified.
House and airconditioner not operated correctly Refer to 'How to operate your house'
Air conditioner too small You can check this using my air conditioner selector
Leaves, papers or other items blocking the coil at the outdoor unit Clear them away
Leaks in ductwork Inspect ductwork with the fan running, particularly at inlet and outlet of air conditioner
Outdoor unit located in a narrow passage at the side of the house or the airflow is restriced in some other way Seek advice
High ceilings and a high level return causing the hot air to remain at ceiling level while you are cold Add a low level return air
Indoor fan continuing to run in winter when compressor is off Read manual to see if control can be changed to set fan off with compressor. (With some air conditioners it is necessary to change this setting at the beginning of summer and beginning of winter.)
Indoor fan shutting off in summer when compressor is off Read manual to see if control can be changed to set fan to continuous. (With some air conditioners it is necessary to change this setting at the beginning of summer and beginning of winter.)
Internal fault in the air conditioner Call service
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Air conditioner regularly trips out Refer also to the previous section  
The circuit breaker is regularly tripping out Check circuit breaker rating
The outdoor temperature is greater than the rated temperature for the air conditioner to remain on line Refer the air conditioner manual for this temperature.
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Some rooms or areas hot and others cold Air balance (amount of air supplied to each room) needs to be altered Contact installer
Grilles need adjusting Adjust grilles
Different temperature behaviour in different rooms (eg large windows facing west in one room and large windows facing east in another room) Try to reduce the heat loads in the hottest rooms (Refer to 'How to operate your house'). Otherwise inividual room control required may be required (expensive).
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Excessive energy use Refer Compressor runs continuously
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Too noisy inside Type or age of air conditioner Box type air conditioners and older air conditioners tend to be noisy and may need to be replaced
Ducts or grilles too small Replace with larger or more ducts
Dirty filter Clean filter
Internal fault in the air conditioner Call service
Back
Too noisy outside Type or age of air conditioner Box type air conditioners and older air conditioners tend to be noisy and may need to be replaced. Seek advice.
Poor location of air conditioner Keep box type air conditioners and outdoor units away from neighbours' windows, especially bedrooms. Seek advice.
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Two story house problems Refer to the individual description of the symptoms  
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