Aircon Error Codes Explained: A Perth Owner Guide

Why your aircon shows an error code

Modern split systems and ducted units constantly monitor themselves. When a sensor reads something outside the normal range, the unit stops or limits operation and displays a code, or flashes a light pattern on the indoor head. That code is the single most useful piece of information you can give a technician, so before you do anything else, write it down exactly as shown.

Error codes exist to protect the system. A unit that shuts down on a refrigerant fault is stopping itself from destroying its own compressor. Repeatedly clearing a code and forcing the unit to run can turn a cheap fix into an expensive one.

First step: the safe reset

Roughly a third of the error calls we attend in Perth clear with a proper power reset. Electronics can latch a one-off glitch, especially after summer brownouts or winter storms in the hills and foothills.

1. Turn the unit off at the remote.
2. Switch off the isolator next to the outdoor unit, or the aircon circuit breaker in your switchboard.
3. Wait a full five minutes so the boards fully discharge.
4. Switch back on and test.

If the code returns within a day or two, the fault is real. Stop resetting and book a repair.

Common codes by brand

Codes differ by brand and model, but these are the ones we see most often in Perth homes.

Daikin

• A3 / A6 - drainage or fan motor issue on the indoor unit. Often a blocked drain, common after a dusty Perth summer.
• E7 - outdoor fan motor fault.
• U0 - low refrigerant. The system needs a leak test, not just a top-up. See our re-gas service.
• U4 - communication fault between indoor and outdoor units, often wiring or a board.

Fujitsu

• Flashing operation and timer lights - count the flashes; the pattern is the code. Note the pattern before resetting.
• E:EE - a stored fault. A technician can pull the exact history.

Mitsubishi Electric

• P8 - outdoor unit temperature abnormality, often refrigerant or a sensor.
• E6 / E7 - indoor to outdoor communication error.

Panasonic

• H11 - communication fault.
• F91 - refrigeration cycle problem, usually low gas or a blockage.

LG

• CH05 / CH53 - communication fault.
• CH38 / CH67 - refrigerant or outdoor fan issues.

Do not panic if your code is not listed. Photograph the display or flashing pattern and quote it when you book online - it usually tells us which parts to bring, which saves you a second call-out fee.

Codes you should never ignore

• Any refrigerant or gas code. Running low on gas overheats the compressor, the most expensive part of the system. This needs a licensed technician and a proper leak test.
• Repeated communication faults. These can point to damaged cabling or failing boards, and occasionally to rodent damage in roof spaces, which we see a lot in older Perth suburbs.
• Codes that return after a reset. Once is a glitch. Twice is a fault.

Preventing error codes in the first place

Most sensor and drainage faults trace back to dirt: clogged filters, blocked drains, and dusty outdoor coils make every sensor work outside its comfort zone. A yearly split system service or ducted service keeps the system clean and catches failing parts before they strand you in a February heatwave.

If your unit is more than ten years old and throwing regular codes, weigh up repair cost against a new inverter system - our guide on repair versus replace covers the maths, and our aircon size calculator will tell you what capacity a replacement needs.

Not sure what your unit is telling you? Grab a photo of the code and book a health check - we service all brands across Perth, from the coast to the Swan Valley.