Error codes and flashing lights

Most systems keep watch on themselves, checking temperatures at several points, fan speeds, the compressor and the communication between the indoor and outdoor units. When something falls outside its expected range, the unit may stop and report it. A code tells an engineer where to start looking, but it doesn't always say which part has failed.

Where codes appear

• The indoor unit's display, as letters and numbers.
• Indicator lights that flash a set number of times, sometimes in a particular colour or combination.
• A remote or wall controller. Some remotes have a button or key sequence that shows the stored code.
• The app, if the system is connected, often with a short description. See Wi-Fi, apps and smart controls.
• The outdoor unit's circuit board, on some models, with lights that can only be seen with the casing off. Those are for an engineer only.

Why a general list won't help

The same code can mean completely different things on different makes, and sometimes on different ranges from the same manufacturer. A list found online that doesn't match your exact model can send you after the wrong fault.

Not every code means a broken part, either. Some report a condition rather than a failure, such as rooms on a multi-split set to different modes, or the unit stopping to protect itself because its airflow is blocked.

How to look up a code

1. Record it. Take a photo of the display or write the code down. For flashing lights, count the flashes over a couple of cycles, as the pattern usually repeats after a pause, and note which light it is and its colour. Write down what mode the system was in, what it was doing and what the weather was like.
2. Find the model number. It's on a label, usually on the side of the indoor unit or under the front panel, and on a rating plate on the outdoor unit. The two units have different model numbers, so note both.
3. Check the user manual. Its troubleshooting section usually lists the codes you can deal with yourself and tells you to contact an installer for the rest. If you've lost the manual, many manufacturers publish manuals online, searchable by model number.
4. Check the app, if you use one.
5. Call the installer. Their details should be in your handover paperwork, and they may be able to tell you what the code means over the phone.

Lights and what they usually mean

What you can safely try

• Deal with anything the manual lists as yours to fix, such as cleaning the filters, clearing the outdoor unit or setting all the rooms on a multi-split to the same mode.
• If the manual suggests a restart, switch off with the remote, then turn the power off at the isolator switch or the system's circuit breaker. Wait a few minutes before switching back on.
• If the code comes back, stop resetting and call an engineer. Repeated restarts can hide a fault that is getting worse.
• If a circuit breaker trips, reset it once at most. If it trips again, leave it off.
• Don't open the casing to look at the circuit board.

When you call, give the code or flash pattern, both model numbers, roughly how old the system is, when the problem started and what you've already tried. Mention anything that happened just before, such as a power cut or building work. Some systems store a fault history that the engineer can read on site. When to call an engineer helps you judge how urgent it is.