When your Carrier system stops and shows a code, that code is the system telling you roughly where the problem is. Roughly is the key word. A fault code points in a direction, it rarely names the exact fix. Find your system below, tap your code, and it will take you straight to what it means and what to do.
Before you try anything: the only DIY steps that are ever safe are switching the system off at the isolator (and waiting 20 to 30 minutes), cleaning or checking filters, checking the controller settings and batteries, and keeping the outdoor unit clear. Anything behind a panel, anything electrical, and anything involving refrigerant or gas is licensed work. If a code below says switch off and call, please take it at its word.
How to read the tables: 🟢 means there is a safe first step worth trying. 🟡 means book a service, the system needs a technician. 🔴 means switch the system off at the isolator and call us on (02) 4760 0100.
Carrier ducted — inverter models (Table 7-1a)
Where the code shows: Two-character code on the indoor unit's digital display ("digital tube"); indoor LEDs (operation, timer, defrost/fan, alarm) flash alongside.
| Code | What it means | What to do |
|---|---|---|
| E8 | The indoor fan motor isn't spinning at the speed it's being asked to. Indoor fan motor speed out of control |
🟡 Book a service. It's safe to try one power-cycle at the isolator first, off for 20 to 30 minutes, then back on. |
| E1 | The indoor and outdoor units have lost contact with each other. Indoor–outdoor communication channel abnormal |
🟢 Switch the system off at the power isolator, wait 20 to 30 minutes, then switch it back on, communication faults often clear after a power interruption or blackout. If the code returns, book a service. |
| E2 | The room temperature sensor isn't reading properly. Room temperature sensor circuit abnormal |
🟡 Book a service, a sensor fault needs a technician to test and replace the part. |
| E3 | A pipe (coil) temperature sensor isn't reading properly. Pipe temperature sensor circuit abnormal (T2 sensor) |
🟡 Book a service, a sensor fault needs a technician to test and replace the part. |
| E4 | A second pipe (coil) temperature sensor isn't reading properly. Pipe temperature sensor circuit abnormal (T2B sensor) |
🟡 Book a service, a sensor fault needs a technician to test and replace the part. |
| E7 | The control board's stored memory has a fault. EEPROM malfunction |
🟡 Try one power-cycle at the isolator (off 20 to 30 minutes). If the code comes back, book a service, the control board likely needs attention. |
| EE | The condensate water level alarm has tripped, the drain tray may not be emptying. Water-level alarm malfunction |
🟡 Switch the system off at the isolator to avoid the drain tray overflowing (with ducted systems it sits in your ceiling space) and book a service. |
| Ed | The outdoor unit has reported a fault. Outdoor unit malfunction (unspecified) |
🟡 Book a service. It's safe to try one power-cycle at the isolator first, and check nothing is blocking the outdoor unit. |
| F3 | Twin indoor units have lost communication with each other. Indoor "twins" (paired indoor units) communication malfunction |
🟢 Switch the system off at the isolator, wait 20 to 30 minutes, then switch it back on, communication faults often clear after a power interruption. If the code returns, book a service. |
| F4 | A fault on a twin (paired) indoor unit setup other than lost communication. Other malfunction of twins configuration |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
Carrier ducted — fixed-speed models (Table 7-1b)
Where the code shows: Two-character code on the indoor unit's digital display; indoor LEDs flash at 5Hz/1Hz.
| Code | What it means | What to do |
|---|---|---|
| E2 | The room temperature sensor isn't reading properly. Room temperature sensor checking channel abnormal. The truncated left column was recovered by re-extracting the source table with layout preserved. |
🟡 Book a service, a sensor fault needs a technician. |
| E3 | The pipe (coil) temperature sensor isn't reading properly. Pipe temperature sensor checking channel abnormal. The truncated left column was recovered by re-extracting the source table with layout preserved. |
🟡 Book a service, a sensor fault needs a technician. |
| E4 | The outdoor temperature sensor isn't reading properly. Outdoor TEMP. sensor checking channel abnormal. Corrected: the earlier 'second pipe/coil sensor' guess (mirrored from the inverter table) was wrong; on the fixed-speed table E4 is the outdoor sensor. |
🟡 Book a service, a sensor fault needs a technician. |
| E5 | The pump temperature sensor isn't reading properly. "Pump temperature sensor malfunction" as written in the source, unusual wording, most likely relates to the condensate/water system |
🟡 Book a service, a sensor fault needs a technician. |
| E7 | The control board's stored memory has a fault. EEPROM malfunction |
🟡 Try one power-cycle at the isolator (off 20 to 30 minutes). If the code comes back, book a service. |
| E8 | The condensate water level alarm has tripped, the drain tray may not be emptying. Water-level alarm malfunction |
🟡 Switch the system off at the isolator to avoid the drain tray overflowing and book a service. |
Alpha AS10-15 (cooling-only models)
Where the code shows: Indoor unit indicator lamps: Operation and Timer (flash / on / off combinations).
Tap your code: Operation flashing, Timer offOperation flashing, Timer onOperation off, Timer flashingOperation on, Timer flashingOperation flashing, Timer flashing
| Code | What it means | What to do |
|---|---|---|
| Operation flashing, Timer off | The indoor fan hasn't run at its commanded speed for over a minute. Indoor fan speed out of control for over 1 minute. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
| Operation flashing, Timer on | The room or indoor-coil temperature sensor circuit is open or shorted. Indoor room temp or evaporator sensor open/short circuit. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🟡 Book a service, a sensor fault needs a technician. |
| Operation off, Timer flashing | The compressor's overcurrent protection has tripped four times. Compressor over-current protection occurred 4 times. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🔴 Switch the system off at the isolator and call us, don't keep restarting it. |
| Operation on, Timer flashing | The control board's stored memory has a fault. EEPROM error. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🟡 Try one power-cycle at the isolator (off 20 to 30 minutes). If it comes back, book a service. |
| Operation flashing, Timer flashing | The control board can't detect the mains zero-crossing signal, a board-level fault. No over-zero (zero-crossing) signal. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
Alpha AS15H (heat pump model)
Where the code shows: Indoor unit indicator lamps: Operation, Timer and Defrost (flash / on / off combinations).
Tap your code: Operation flashing, Timer off, Defrost flashingOperation off, Timer flashing, Defrost flashingOperation flashing, Timer flashing, Defrost flashingOperation off, Timer off, Defrost flashingOperation off, Timer flashing, Defrost offOperation on, Timer flashing, Defrost off
| Code | What it means | What to do |
|---|---|---|
| Operation flashing, Timer off, Defrost flashing | The compressor's overcurrent protection has tripped four times. Compressor over-current protection occurred 4 times. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🔴 Switch the system off at the isolator and call us, don't keep restarting it. |
| Operation off, Timer flashing, Defrost flashing | The indoor fan hasn't run at its commanded speed for over a minute. Indoor fan speed out of control for over 1 minute. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
| Operation flashing, Timer flashing, Defrost flashing | The control board can't detect the mains zero-crossing signal, a board-level fault. No over-zero (zero-crossing) signal. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
| Operation off, Timer off, Defrost flashing | The indoor-coil temperature sensor circuit is open or shorted. Indoor evaporator temperature sensor open/short circuit. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🟡 Book a service, a sensor fault needs a technician. |
| Operation off, Timer flashing, Defrost off | The room temperature sensor circuit is open or shorted. Indoor room temperature sensor open/short circuit. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🟡 Book a service, a sensor fault needs a technician. |
| Operation on, Timer flashing, Defrost off | The control board's stored memory has a fault. EEPROM error. Lamp-to-fault pairing confirmed by layout re-extraction of the source table. |
🟡 Try one power-cycle at the isolator (off 20 to 30 minutes). If it comes back, book a service. |
Alpha AS35C/H — indoor unit
Where the code shows: Indoor unit indicator lamps flashing at 5Hz (operation / timer / defrost — defrost lamp doubles as fan lamp on cooling-only units — plus auto).
Tap your code: Operation + Timer + Defrost lamps flashing (5Hz)Timer lamp flashing (5Hz)Operation lamp flashing (5Hz)Defrost lamp flashing (5Hz)Defrost + Auto lamps flashing (5Hz)
| Code | What it means | What to do |
|---|---|---|
| Operation + Timer + Defrost lamps flashing (5Hz) | The compressor's current protection has tripped four times. Current protection (PRCUR1) occurred 4 times. In the AS35C/H table the pattern is Operation + Timer + Defrost; the AS15H copy of the same list adds the auto lamp, confirmed by layout re-extraction. |
🔴 Switch the system off at the isolator and call us, don't keep restarting it. |
| Timer lamp flashing (5Hz) | The room temperature sensor circuit is open or shorted. Room temperature sensor open/short |
🟡 Book a service, a sensor fault needs a technician. |
| Operation lamp flashing (5Hz) | The indoor-coil temperature sensor circuit is open or shorted. Evaporator temperature sensor open/short |
🟡 Book a service, a sensor fault needs a technician. |
| Defrost lamp flashing (5Hz) | The outdoor-coil temperature sensor circuit is open or shorted. Condenser temperature sensor open/short |
🟡 Book a service, a sensor fault needs a technician. |
| Defrost + Auto lamps flashing (5Hz) | The outdoor unit has gone into a protection mode (for example its outdoor temperature sensor or the power phase order). Outdoor unit protection (outdoor temp sensor, phase order etc.). Both copies of the table agree on Defrost + Auto, confirmed by layout re-extraction. |
🟡 Book a service. It's safe to try one power-cycle at the isolator first, and check nothing is blocking the outdoor unit. |
Alpha AS35C/H — outdoor unit
Where the code shows: Outdoor unit LED: counts a number of flashes, pauses 2 seconds, repeats (steady on = normal running).
| Code | What it means | What to do |
|---|---|---|
| 5 flashes | The outdoor unit has lost contact with the indoor unit. Communication error |
🟢 Switch the system off at the isolator, wait 20 to 30 minutes, then switch it back on, communication faults often clear after a power interruption. If it returns, book a service. |
| 4 flashes | The power supply phases are connected in the wrong order, so the unit is protecting itself. Phase order protection (three-phase supply) |
🟡 Book a service, this is an electrical supply issue a technician needs to check. Don't keep restarting the unit. |
| 3 flashes | The refrigerant circuit pressure has gone outside safe limits and the unit has shut itself down. Pressure protection |
🔴 Switch the system off at the isolator and call us, pressure faults can point to a refrigerant problem. |
| 2 flashes | The outdoor-coil temperature sensor circuit is open or shorted. Condenser temperature sensor open/short |
🟡 Book a service, a sensor fault needs a technician. |
| 1 flash | The indoor unit has reported a problem. Indoor unit abnormal |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
Alpha Inverter
Where the code shows: Four indoor LEDs in the order defrost, timer, auto, operation (O = on, X = off, ☆ = flash) — column order confirmed from the table's second header line (LED2 defrost / LED1 timer / LED3 auto / LED4 operation) in a layout re-extraction. Outdoor: L4 flashing at 1Hz = fault, steady on = running, 0.5Hz = standby..
| Code | What it means | What to do |
|---|---|---|
| X X O ☆ | The unit is in its mould-prevention (drying) protection mode rather than a breakdown. Listed as "mold protection" in the fault table, the anti-mould/self-dry routine; it sits in the error list, so treat a persistent pattern with caution. Pattern-to-meaning pairing confirmed by layout re-extraction. |
🟢 Let the cycle finish. If the lamps stay like this or the unit won't run afterwards, switch it off at the isolator for 20 to 30 minutes; if it persists, book a service. |
| O X X ☆ | The top of the compressor has overheated and the unit has shut down to protect it. Compressor top temperature protection |
🔴 Switch the system off at the isolator and call us, overheating can point to a refrigerant or compressor problem. |
| X O X ☆ | The outdoor temperature sensor circuit is open or shorted. Outdoor temperature sensor open/short circuit |
🟡 Book a service, a sensor fault needs a technician. |
| X O O ☆ | The unit has shut down because the power supply voltage is too high or too low, or it's overloaded. Overload or under/over-voltage protection |
🟡 Switch off at the isolator for 20 to 30 minutes and try again, voltage dips after grid events can trip this. If it keeps happening, book a service. |
| O O O ☆ | The room or indoor-coil temperature sensor circuit is open or shorted. Room or evaporator temperature sensor open/short circuit |
🟡 Book a service, a sensor fault needs a technician. |
| O O ☆ ☆ | The indoor fan isn't spinning at the speed it's being asked to. Fan speed beyond control |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
| ☆ X O ☆ | The control board can't detect the mains zero-crossing signal, a board-level fault. Zero-crossing examination error |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
| X X ☆ ☆ | The control board's stored memory has a fault. EEPROM data error |
🟡 Try one power-cycle at the isolator (off 20 to 30 minutes). If it comes back, book a service. |
| ☆ ☆ ☆ ☆ | The indoor and outdoor units have lost contact with each other. Indoor/outdoor communication protection |
🟢 Switch the system off at the isolator, wait 20 to 30 minutes, then switch it back on, communication faults often clear after a power interruption. If it returns, book a service. |
Elite 42LUVH055N / 42LUVH065N (N series)
Where the code shows: E/P code on the indoor unit display.
| Code | What it means | What to do |
|---|---|---|
| E0 | The control board's stored memory has a fault. EEPROM parameter error |
🟡 Try one power-cycle at the isolator (off 20 to 30 minutes). If the code comes back, book a service. |
| E1 | The indoor and outdoor units have lost contact with each other. Indoor/outdoor communication protection |
🟢 Switch the system off at the isolator, wait 20 to 30 minutes, then switch it back on, communication faults often clear after a power interruption. If the code returns, book a service. |
| E2 | The control board can't detect the mains zero-crossing signal, a board-level fault. Zero-crossing signal error |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
| E3 | The indoor fan isn't spinning at the speed it's being asked to. Fan speed out of control |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
| E5 | The outdoor temperature sensor circuit is open or shorted. Outdoor temperature sensor open/short circuit |
🟡 Book a service, a sensor fault needs a technician. |
| E6 | The room or indoor-coil temperature sensor circuit is open or shorted. Room or evaporator temperature sensor open/short circuit |
🟡 Book a service, a sensor fault needs a technician. |
| E7 | The outdoor unit's fan has a problem and its protection has kicked in. Outdoor unit fan protection |
🟡 Check nothing is blocking or tangled in the outdoor unit (from the outside only), then book a service. |
| P0 | The inverter power module has shut down to protect itself from an electrical fault. Module protection (inverter power module / IPM) |
🔴 Switch the system off at the isolator and call us, don't keep restarting it. |
| P1 | The unit has shut down because the power supply voltage is too high or too low. Over-voltage or under-voltage protection |
🟡 Switch off at the isolator for 20 to 30 minutes and try again, voltage dips after grid events can trip this. If it keeps happening, book a service. |
| P2 | The top of the compressor has overheated and the unit has shut down to protect it. Compressor top temperature protection |
🔴 Switch the system off at the isolator and call us, overheating can point to a refrigerant or compressor problem. |
| P4 | The electronics that drive the inverter compressor have reported a fault. Inverter compressor drive error. E4 and P3 are reserved (unused) on this series. |
🔴 Switch the system off at the isolator and call us, repeated restarts can stress the compressor. |
Elite 42LUVH075N
Where the code shows: Indoor lamps in on/off/flash combinations, listed in the source column order Defrost · Timer · Auto · Operation (On = steady, X = off, ☆ = flash at 5Hz). The operation lamp flashes in every fault pattern..
Tap your code: Def On · Timer On · Auto On · Op OnDef ☆ · Timer ☆ · Auto ☆ · Op ☆Def X · Timer On · Auto X · Op ☆Def On · Timer On · Auto On · Op ☆Def X · Timer X · Auto On · Op ☆Def X · Timer On · Auto On · Op ☆Def On · Timer X · Auto X · Op ☆Def On · Timer X · Auto On · Op ☆Def On · Timer X · Auto ☆ · Op ☆
| Code | What it means | What to do |
|---|---|---|
| Def On · Timer On · Auto On · Op On | The control board's stored memory has a fault. EEPROM parameter error |
🟡 Try one power-cycle at the isolator (off 20 to 30 minutes). If it comes back, book a service. |
| Def ☆ · Timer ☆ · Auto ☆ · Op ☆ | The indoor and outdoor units have lost contact with each other. Indoor/outdoor communication protection |
🟢 Switch the system off at the isolator, wait 20 to 30 minutes, then switch it back on, communication faults often clear after a power interruption. If it returns, book a service. |
| Def X · Timer On · Auto X · Op ☆ | The outdoor temperature sensor circuit is open or shorted. Outdoor temperature sensor open/short circuit |
🟡 Book a service, a sensor fault needs a technician. |
| Def On · Timer On · Auto On · Op ☆ | The room or indoor-coil temperature sensor circuit is open or shorted. Room or evaporator temperature sensor open/short circuit |
🟡 Book a service, a sensor fault needs a technician. |
| Def X · Timer X · Auto On · Op ☆ | The inverter power module has shut down to protect itself from an electrical fault. Module protection (inverter power module / IPM) |
🔴 Switch the system off at the isolator and call us, don't keep restarting it. |
| Def X · Timer On · Auto On · Op ☆ | The unit has shut down because the power supply voltage is too high or too low. Over-voltage or under-voltage protection |
🟡 Switch off at the isolator for 20 to 30 minutes and try again, voltage dips after grid events can trip this. If it keeps happening, book a service. |
| Def On · Timer X · Auto X · Op ☆ | The top of the compressor has overheated and the unit has shut down to protect it. Compressor top temperature protection |
🔴 Switch the system off at the isolator and call us, overheating can point to a refrigerant or compressor problem. |
| Def On · Timer X · Auto On · Op ☆ | The outdoor temperature is too low for the unit to run, so it's protecting itself. Outdoor temperature low protection (075N only, not in the 055N/065N code list) |
🟡 This usually clears when the weather warms up. If it appears in mild conditions, book a service. |
| Def On · Timer X · Auto ☆ · Op ☆ | The electronics that drive the inverter compressor have reported a fault. Inverter compressor drive error |
🔴 Switch the system off at the isolator and call us, repeated restarts can stress the compressor. |
Elite 025N-1 to 075N-1 (N-1 series)
Where the code shows: E/P code on the indoor unit display.
| Code | What it means | What to do |
|---|---|---|
| E0 | The control board's stored memory has a fault. EEPROM parameter error. Manual's own first step is a power-off/on reset; if it recurs, the indoor PCB is suspect. |
🟡 Try one power-cycle at the isolator (off 20 to 30 minutes). If the code comes back, book a service. |
| E1 | The indoor and outdoor units have lost contact with each other. Indoor/outdoor communication protection. Manual's own first step is a 1-minute power-off reset before any wiring checks. |
🟢 Switch the system off at the isolator, wait 20 to 30 minutes, then switch it back on, communication faults often clear after a power interruption. If the code returns, book a service. |
| E2 | The control board can't detect the mains zero-crossing signal, a board-level fault. Zero-crossing signal error. Manual states this indicates a faulty main control board. |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
| E3 | The indoor fan isn't spinning at the speed it's being asked to. Indoor fan speed out of control |
🟡 Book a service. It's safe to try one power-cycle at the isolator first. |
| E5 | Either the outdoor temperature sensor circuit is open or shorted, or the outdoor unit's control board memory has a fault. Outdoor temperature sensor open/short OR outdoor unit EEPROM parameter error (broader than E5 on the N series) |
🟡 Book a service, this needs a technician to test the sensor and outdoor board. |
| E6 | The room or indoor-coil temperature sensor circuit is open or shorted. Room or evaporator coil temperature sensor open/short circuit |
🟡 Book a service, a sensor fault needs a technician. |
| E7 | The outdoor fan isn't spinning at the speed it's being asked to. Outdoor fan speed out of control (N series wording for E7 is "outdoor unit fan protection") |
🟡 Check nothing is blocking or tangled in the outdoor unit (from the outside only), then book a service. |
| P0 | The inverter power module has shut down because of an electrical fault or excessive current. IPM malfunction or IGBT over-current protection (source misprints IPM as "IBM") |
🔴 Switch the system off at the isolator and call us, don't keep restarting it. |
| P1 | The unit has shut down because the power supply voltage is too high or too low. Over-voltage or under-voltage protection |
🟡 Switch off at the isolator for 20 to 30 minutes and try again, voltage dips after grid events can trip this. If it keeps happening, book a service. |
| P2 | The top of the compressor has overheated and the unit has shut down to protect it. Compressor top temperature protection. Manual's diagnosis path includes refrigerant charge and circuit blockage checks. |
🔴 Switch the system off at the isolator and call us, overheating can point to a refrigerant or compressor problem. |
| P4 | The electronics that drive the inverter compressor have reported a fault. Inverter compressor drive error. E4 and P3 are reserved (unused) on this series. |
🔴 Switch the system off at the isolator and call us, repeated restarts can stress the compressor. |
Code still showing after a reset? Mention the code and your system type when you book and our office can line up the right technician and likely parts before we arrive.
Book a service or call (02) 4760 0100 (24-hour line, Penrith & Blue Mountains).
Codes vary between models and generations, and manufacturers revise them. This guide is compiled from official service documentation and checked by Ample Air, but it is general information, not a diagnosis. Refrigerant and electrical work must be carried out by licensed technicians. Ample Air, ARC licences AU12976 & AU15788. Last verified August 2026.