Air conditioning error codes: how to read them and what to do

How error codes work

Your system constantly checks its own sensors, fan motors, compressor, pressures and the signal between the indoor and outdoor units. When a reading goes outside safe limits, it stops and shows a code. On Mitsubishi Electric wall units, for example, the indoor fan stops and the operation light blinks.

A code points to an area, not always to the failed part. A communication code can be caused by wiring, a control board or the power supply. Some codes are protection stops rather than broken parts: Daikin's A5, for example, is freeze-up protection, which poor airflow from dirty filters can trigger.

Each manufacturer uses its own codes, and the same code can mean different things on different brands or models. Always read it alongside the brand and model number.

How each brand shows its codes

Examples come from each manufacturer's own manuals and support pages. Check your model's manual, as codes vary between ranges.

How to read the code on your unit

1. 1

   Look before you reset

   Write down any code on the display or controller. If lights are flashing, count the blinks of each light over at least two full cycles, as Mitsubishi Electric's service manual advises. A phone video helps.

2. 2

   Daikin wireless remotes

   On many models you hold one button for about five seconds until the temperature area blinks, then press it repeatedly until the unit gives a long, continuous beep. The code then shown is the fault.

3. 3

   Panasonic remotes

   Panasonic's method is to hold the CHECK button for about five seconds with a pointed object until the display shows two dashes, then step through codes with the timer buttons until the unit beeps. Newer remotes use a System check menu.

4. 4

   LG and Mitsubishi Electric

   Read the code on the display or count the blinks. Mitsubishi Electric's remote recall mode changes remote settings and must be cancelled after use, so leave that to an engineer.

5. 5

   Note the model number

   Find the label on the side of the indoor unit and photograph it. Daikin's manual asks for the full model name, the serial number if possible and the installation date.

What you can safely try

Once you've written the code down, these are safe for any owner.

• Check the basics: mode, set temperature, timers and remote batteries
• Switch off, then clean the filters. Clogged filters can trigger protection codes
• Make sure nothing is blocking the outdoor unit or its fan
• Reset once: switch off with the remote, then at the isolator or breaker. LG advises waiting 5 minutes before restoring power
• If the code returns, stop there. It's a real fault and needs an engineer
• Panasonic Comfort Cloud users can check error notifications in the app

Brand by brand guides

We've written a separate guide for each brand we install, with its common codes, what they usually mean and what to check. Pick yours from the links at the end of this page: Daikin, Mitsubishi Electric, LG or Panasonic.

If your unit is another make, the same approach works. Note the code and model number, try one reset, and book a visit if it comes back. We repair most split systems, including ones we didn't fit.

What a diagnostic visit costs

The visit covers the first hour on site, where the engineer confirms the fault behind the code and gives you a written price. If you go ahead with the repair, we take it off the bill.

• Repair diagnostic visit

  First hour on site, deducted if you go ahead

  from£125inc. VAT

Error code questions