Alliance air conditioner error codes
Displayed on the indoor unit or remote when a fault is detected. Always isolate power before inspecting a unit — repairs belong to a qualified technician.
| Code | Meaning | Applies to | |
|---|---|---|---|
| E0 | Meaning depends on unit type — Inverter midwall: EEPROM error; Inverter under-ceiling/cassette/ducted: communication between indoor and outdoor units; Package unit: phase rotation / phase missing; Integrated water heater: error of sensor T5U. | All models | Details |
| E1 | Meaning depends on unit type — Vertu fixed-speed midwall / Fixed-speed under-ceiling/cassette/ducted: EEPROM error; Atlantic midwall: outdoor tube sensor fault; Inverter midwall: indoor-outdoor communication error; Inverter under-ceiling/cassette/ducted / Pool heater / Commercial water heater: phase rotation / phase missing; Package unit: outdoor coil sensor, system A; Portable: room temperature sensor error; Water heater (retrofit): phase reversal / phase missing error; Integrated water heater: error of sensor T5L. | All models | Details |
| E2 | Meaning depends on unit type — Vertu fixed-speed midwall / Inverter midwall / Fixed-speed under-ceiling/cassette/ducted: zero-crossing detection error; Atlantic midwall: room temperature sensor open or short circuit; Inverter under-ceiling/cassette/ducted: communication error between indoor unit and master unit; MAC cassette: room temperature sensor failure; Package unit: outdoor coil sensor, system B; Portable: evaporator temperature sensor error; Water heater (retrofit): communication error between unit and wired control, or sensor damaged; Pool heater: outdoor unit and wire controller communication error; Integrated water heater: tank and wired controller communication error; Commercial water heater: communication failure between wired remote and main unit. | All models | Details |
| E3 | Meaning depends on unit type — Vertu fixed-speed midwall / Inverter midwall / Fixed-speed under-ceiling/cassette/ducted: indoor fan error; Atlantic midwall: indoor coil sensor open or short circuit; MAC cassette: coil temperature sensor failure; Portable: condenser temperature sensor error; Water heater (retrofit) / Pool heater: outlet water temperature sensor error; Commercial water heater: outlet water temperature sensor failure. | All models | Details |
| E4 | Meaning depends on unit type — Inverter midwall: indoor room temperature sensor open or short circuit; Inverter under-ceiling/cassette/ducted: outdoor temperature sensor error; MAC cassette: condenser sensor failure; Water heater (retrofit): water temperature sensor failure in the water tank; Pool heater: inlet water temperature sensor error; Integrated water heater: condenser pipe temperature sensor error; Commercial water heater: water temperature sensor in the water tank failure. | All models | Details |
| E5 | Meaning depends on unit type — Vertu fixed-speed midwall / Fixed-speed under-ceiling/cassette/ducted: room temperature sensor open or short circuit; Atlantic midwall: indoor fan fault; Inverter midwall: indoor coil sensor open or short circuit; Inverter under-ceiling/cassette/ducted: compressor discharge temperature sensor error; MAC cassette: water pump temperature sensor error; Package unit: indoor coil sensor, system A; Water heater (retrofit): condenser temperature sensor error; Pool heater: evaporator pipe temperature sensor error; Integrated water heater: outdoor ambient temperature sensor error; Commercial water heater: condenser temperature sensor failure. | All models | Details |
| E6 | Meaning depends on unit type — Vertu fixed-speed midwall / Fixed-speed under-ceiling/cassette/ducted: indoor coil sensor open or short circuit; Atlantic midwall: EEPROM error; MAC cassette: outdoor malfunction; Package unit: indoor coil sensor, system B; Water heater (retrofit): outdoor ambient temperature sensor error; Integrated water heater: sensor Tp error; Commercial water heater: outdoor ambient temperature sensor failure. | All models | Details |
| E7 | Meaning depends on unit type — Atlantic midwall: external feedback fault (check interconnecting wiring); MAC cassette: EEPROM malfunction; Water heater (retrofit): sensor failure at water pump outlet; Pool heater: ambient temperature sensor error; Commercial water heater: electric heating pipe temperature sensor failure. | All models | Details |
| E8 | Meaning depends on unit type — Atlantic midwall: overheat detection / defrosting; Inverter under-ceiling/cassette/ducted: outdoor unit address error; MAC cassette: water-level alarm; Integrated water heater: electric leakage protection. | All models | Details |
| E9 | Meaning depends on unit type — Inverter under-ceiling/cassette/ducted: power voltage error; Package unit: indoor temperature sensor error; Water heater (retrofit): T8 temperature sensor error; Pool heater: water flow switch error. | All models | Details |
| EA | Outdoor ambient sensor error (Package unit units). | All models | Details |
| EB | Meaning depends on unit type — Package unit: wire controller output error; Commercial water heater: exhaust temperature sensor error (TP). | All models | Details |
| EC | Meaning depends on unit type — Vertu fixed-speed midwall / Inverter midwall / Fixed-speed under-ceiling/cassette/ducted: refrigerant leak detected; Commercial water heater: water inlet temperature sensor error. | All models | Details |
| ED | Sensor failure at double-pipe refrigerant outlet (Water heater (retrofit) units). | All models | Details |
| EE | Discharge pipe temperature sensor error (Pool heater units). | All models | Details |
| F0 | Low refrigerant protection. | All models | Details |
| F1 | Outdoor temperature sensor open or short circuit (Inverter midwall units). | All models | Details |
| F2 | Condenser coil sensor open or short circuit (Inverter midwall units). | All models | Details |
| F3 | Compressor discharge sensor open or short circuit (Inverter midwall units). | All models | Details |
| F4 | Outdoor EEPROM error (Inverter midwall units). | All models | Details |
| FT | Full tray or full tank (Portable units). | All models | Details |
| H0 | Communication malfunction between IR341 and 780034 chips (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| H1 | Communication between 0537/9177 and 780034 chips (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| H2 | Quantity of outdoor units decreased (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| H3 | Quantity of outdoor units increased (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| H4 | P6 protection detected 3 times (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| H5 | P2 detected 3 times in 30 minutes (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| H6 | P4 detected 3 times in 100 minutes (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| H7 | Indoor unit decrease error (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| H8 | Discharge pressure sensor error (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| H9 | P9 detected 3 times in 30 minutes (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| HO | Indoor and outdoor units unmatched (Water heater (retrofit) units). | All models | Details |
| HP | High-pressure alarm (Portable units). | All models | Details |
| L0 | DC inverter module protection (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| L1 | DC supply low voltage (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| L2 | DC supply high-voltage protection (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| L4 | MEC failure (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| L8 | Frequency protection (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| L9 | Frequency protection (Inverter under-ceiling/cassette/ducted units). | All models | Details |
| LA | Ambient temperature is outside the 5-43 °C range (Integrated water heater units). | All models | Details |
| LT | Low temperature (Portable units). | All models | Details |
| P0 | Meaning depends on unit type — Inverter midwall: IPM malfunction or IGBT over-current; Inverter under-ceiling/cassette/ducted: inverter compressor top temperature protection; Package unit: overcurrent protection, system A; Pool heater: discharge pressure over-high protection; Integrated water heater: condenser pipe temperature overflow protection; Commercial water heater: system LP protection. | All models | Details |
| P1 | Meaning depends on unit type — Inverter midwall: over- or under-voltage protection; Inverter under-ceiling/cassette/ducted: high-pressure protection; Package unit: overcurrent protection, system B; Portable: bottom tray is full; Water heater (retrofit): HP protection / air in system / pump not starting / no water; Pool heater: low-pressure protection; Commercial water heater: system HP protection (check circulating pump). | All models | Details |
| P2 | Meaning depends on unit type — Inverter midwall: compressor top temperature protection (normally shortage of refrigerant); Inverter under-ceiling/cassette/ducted: low-pressure protection; Package unit: overcurrent protection for outdoor fan; Water heater (retrofit): system current protection; Integrated water heater: high discharge temperature; Commercial water heater: current protection, system 2. | All models | Details |
| P3 | Meaning depends on unit type — Inverter under-ceiling/cassette/ducted: inverter compressor current protection; Package unit: comprehensive protection for outdoor fan; Integrated water heater: open compressor circuit protection; Commercial water heater: current protection, system 1. | All models | Details |
| P4 | Meaning depends on unit type — Inverter midwall: inverter compressor drive error; Inverter under-ceiling/cassette/ducted: compressor discharge temperature protection (shortage of refrigerant); Package unit: HP/LP or discharge temperature protection, system A; Water heater (retrofit): tt HP protection; Pool heater: compressor over-current protection; Integrated water heater: compressor overcurrent protection. | All models | Details |
| P5 | Meaning depends on unit type — Inverter under-ceiling/cassette/ducted: outdoor condenser high-temperature protection; Package unit: HP/LP or discharge temperature protection, system B; Water heater (retrofit): condenser HP protection. | All models | Details |
| P6 | Meaning depends on unit type — Inverter under-ceiling/cassette/ducted: inverter module protection; Package unit: HP protection in T2 evaporator — stops the outdoor unit fan; Pool heater: evaporator over-temperature protection. | All models | Details |
| P7 | Meaning depends on unit type — Inverter under-ceiling/cassette/ducted: current protection, fixed compressor No. 1; Package unit: HP protection in T2 evaporator — stops the outdoor unit fan and compressor. | All models | Details |
| P8 | Meaning depends on unit type — Inverter under-ceiling/cassette/ducted: current protection, fixed compressor No. 2; Package unit: condenser high-temperature protection, system A; Water heater (retrofit): protection for over-temperature at condenser outlet; Integrated water heater: open upper e-heater circuit protection; Commercial water heater: protection for excessively high outlet water temperature. | All models | Details |
| P9 | Meaning depends on unit type — Inverter under-ceiling/cassette/ducted: fan motor protection; Package unit: condenser high-temperature protection, system B; Water heater (retrofit): anti-freezing protection; Integrated water heater: upper e-heater overload protection. | All models | Details |
| PA | Open lower e-heater circuit protection (Integrated water heater units). | All models | Details |
| PB | Meaning depends on unit type — Water heater (retrofit) / Commercial water heater: anti-freezing protection; Pool heater: anti-freeze protection; Integrated water heater: lower e-heater overload protection. | All models | Details |
| PC | Anti-freezing protection for evaporator, system A (Package unit units). | All models | Details |
| PD | Anti-freezing protection for evaporator, system B (Package unit units). | All models | Details |
| PF | Meaning depends on unit type — Package unit: defrosting; Portable: probe failure; Pool heater: discharge temperature protection (too high). | All models | Details |