Daikin air conditioner fault codes

Daikin are the one manufacturer here who put the fault code table in the owner’s manual rather than hiding it in an installer document, and they publish how to get the code out of the remote. Reading it is your job. Almost nothing on the list is.

Where the code shows on a Daikin

Two characters, retrieved through the remote rather than shown on a screen. Hold Cancel for five seconds until a blinking 00 appears, then press Cancel repeatedly — a short beep or two beeps means the code showing is not yours, and a long continuous beep means it is. Daikin print the table in three groups, SYSTEM, INDOOR UNIT and OUTDOOR UNIT, which tells you where the fault is before you have looked anything up. One more check before you do: Daikin’s Altherma heat pumps use the same two-character vocabulary, and U0, U4 and A5 appear in both tables with the same headline fault and a different machine behind it. If your Daikin heats radiators or a hot water cylinder rather than blowing air from a wall unit, the pages in our heat-pumps section carry the checks for an Altherma.

How to reset a Daikin

Daikin publish exactly one owner reset, and it is narrow. If operation stopped suddenly and the OPERATION lamp is flashing, their instruction is to clean the air filters, remove anything blocking the air inlets and outlets of the indoor and outdoor units, turn the breaker off and on again, and try again with the remote — and if the lamp still flashes, to call the service shop. They give the same breaker off-and-on for a unit misbehaving after lightning or radio interference. There is no per-code reset beyond that, and the codes themselves are not cleared by it in any useful sense: retrieve the code first, then cycle the breaker once, and if it comes back you have a real fault and a code to hand over. To clear the retrieval display, hold Cancel for five seconds or leave it alone for a minute. On multi-split outdoor units Daikin also publish an LED pattern table, but reading it means removing a cover on a live outdoor unit, so it is not an owner diagnostic whatever it looks like online.

Most common Daikin faults

The Daikin codes people look up most.

Every Daikin fault code

5 published codes. Filtering happens in the page — every one is in the HTML.

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Showing 5 of 5 codes

Every published Daikin fault code with its meaning and severity
Code	What it means	Severity
U0	Refrigerant shortage. The circuit is sealed, so if it is short it has leaked — and this is certified work by law, not a top-up.	Get it checked
A5	Freeze-up protection or high pressure control. A filthy indoor filter is a legitimate published cause, which makes this the one on the list worth checking yourself.	Get it checked
U4	The indoor and outdoor units have stopped talking. Daikin’s own cause list starts with the mains supply and the inter-unit cable, so one breaker cycle is worth a try before anyone is called.	Get it checked
E6	The compressor failed to start. It sits in Daikin’s outdoor unit group alongside the overload and pressure codes, and all of them are certified work.	Get it checked
00	Not a fault. Daikin publish 00 as NORMAL, and it is also what shows while you are stepping through the diagnostic.	Usually simple to fix

Daikin models

Codes can differ between generations. Check yours.

Guides that help with Daikin faults

Air conditioning not cooling, dripping or stopped: checks
A split has no screen, so get the code out first; on a Toshiba, before touching the power. Then the filter, drain and isolator, and where F-Gas work begins.Read the guide

Looking for Daikin’s own support? www.daikin.co.uk. We are not affiliated with Daikin.