Air Conditioning Error Codes by Brand
A code on the display or a blinking lamp is the unit telling you which part of itself is unhappy. How each major brand structures its codes, the most commonly reported ones, and what to try before calling an F-Gas engineer. Always confirm against your model's manual.
Reading a fault code
Most splits report faults one of three ways: an alphanumeric code on the indoor display, a blink pattern on the operation or timer lamp, or a code retrieved through a check mode on the remote. The first character usually says where — indoor, outdoor, communication or protection — and the second narrows it to a component: sensor, fan, pump, pressure or compressor.
That is why a code is worth noting before anything else: it turns "it stopped working" into "the outdoor fan is not reporting speed" — a shorter, cheaper visit. Codes below are the most commonly reported; meanings vary between models and generations, so treat them as pointers, not a diagnosis.
Commonly reported codes by manufacturer
| Brand | Code style | Commonly reported codes (check your manual) |
|---|---|---|
| Daikin | Letter + digit on display, or via remote check mode; first letter = area (A indoor, E outdoor, U system/comms, C/J sensors) | U4 indoor–outdoor communication · E7 outdoor fan motor · A5 high pressure / freeze protection · A1 indoor PCB · A6 indoor fan motor · U0 refrigerant shortage · E5 compressor overload |
| Mitsubishi Electric | Operation-lamp blink counts on M-series wall units; P, E and U codes on wired controllers and Mr Slim | P1 / P2 intake or pipe thermistor · P4 drain float sensor · P5 drain pump / overflow · P6 freeze or overheat protection · E0–E7 remote, indoor or outdoor communication · UF compressor overcurrent |
| Fujitsu | Operation / timer / economy lamp flash counts on wall units; E codes on wired controllers | Lamp patterns commonly reported for indoor–outdoor communication, temperature sensors, outdoor fan motor, discharge temperature and compressor faults — count flashes of each lamp in one cycle and decode against the model manual |
| Panasonic | H codes (indoor side) and F codes (outdoor/protection) on display, or via remote check mode | H11 indoor–outdoor communication · H19 indoor fan motor · H23 indoor heat-exchanger sensor · F91 refrigerant cycle abnormal · F97 compressor discharge temperature · F99 DC overcurrent |
| LG | CH (check) codes, two digits, on display or lamp blinks | CH05 indoor–outdoor communication · CH10 indoor fan lock · CH21 DC peak / inverter · CH22 compressor overcurrent · CH38 refrigerant shortage / leak |
| Samsung | E + three digits; E1xx indoor, E2xx comms, E4xx outdoor/compressor, E5xx system | E101 indoor–outdoor communication · E121 room temperature sensor · E154 indoor fan · E458 outdoor fan · E461 compressor start failure · E554 refrigerant leak |
Disclaimer: codes and meanings differ by model, generation and system type (split, multi-split, VRF/VRV). Always confirm against the manual or the manufacturer's published list for your exact model. Toshiba and Hitachi use comparable letter-digit systems.
What you can do before calling — and when to call
| Step | Do it yourself? | Notes |
|---|---|---|
| Note the exact code or blink pattern and which unit shows it | Yes | Photograph the display; count blinks in one full cycle |
| Power cycle: off at isolator for ten minutes, restart | Yes | Clears transient comms and protection codes; if it returns, stop |
| Clean filters; check outdoor unit for leaves, covers, blocked fins | Yes | Resolves many pressure, freeze and fan-speed codes |
| Open the unit, reseat connectors, test sensors | No | Mains voltage and charged capacitors inside |
| Respond to refrigerant, pressure, compressor or inverter codes | Call an F-Gas engineer | These need gauges, a meter and certification |
Diagnosis is normally covered by a call-out of £80–£150. Leak-related codes add a repair and re-gas at £100–£300. Full costs in air conditioning repair costs.
What the code usually costs to fix
Sensor and communication faults sit at the cheap end: a thermistor, connector or cable inside a standard call-out plus a modest part. Fan codes add the motor. Pressure and freeze-protection codes are often airflow and clear with a clean; where they mean low charge, the leak must be repaired before a re-gas. Compressor and inverter-board codes on a unit past ten years are the ones to weigh against a new system at £1,500–£3,000 for a single split — see repair or replace?. Units within a 5–7 year warranty should go back to the installer first.
Code plus weak cooling: read not cooling; plus water indoors, leaking water; plus a tripping breaker, noisy or tripping.
Sources & methodology
- Code families summarised from publicly available manufacturer manuals for Daikin, Mitsubishi Electric, Fujitsu, Panasonic, LG and Samsung; listed codes are those most commonly reported and meanings vary by model.
- Refrigerant and pressure work only by F-Gas certified persons under the GB F-Gas Regulation.
- Price baselines are 2026 UK figures used across this site: call-out £80–£150, re-gas £100–£300, single split installed £1,500–£3,000.
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