General Assist Technical Reference
AOTG36LBLA5 / AOTG45LBLA6 Multi-Split Troubleshooting
Error codes, diagnostic flow and component test values
R410A inverter multi systems – service troubleshooting reference
This guide consolidates the troubleshooting information for the LBLA 36/45 multi system family, including indoor and outdoor error displays, no-error fault finding and key component test values.
Safety: Electrical testing must only be carried out by appropriately qualified service personnel. Isolate power before disconnecting or reconnecting wiring, PCB connectors, thermistors, fan motors, EEV coils or compressor terminals. Live voltage checks must be performed using suitable test equipment and safe work practices.
1. Reading the error display
Wired remote controller
When Er is shown in the temperature display, inspect the system. The display identifies the unit number and error code. Up to 16 memorised error codes can also be reviewed from the wired remote controller error-history mode.
Simple remote controller
If an error occurs, Er is displayed together with the faulty unit number and error code.
Outdoor unit LEDs
The outdoor PCB uses the ERROR LED and monitor LEDs A–F to identify the fault. The ERROR LED flashes rapidly and the monitor LEDs indicate the error location/code. Briefly pressing SW1 displays the stored error code.
2. Error code quick reference
| Error | Fault description | Operation lamp | Timer lamp |
|---|---|---|---|
| 11 | Serial communication error | 1 flash | 1 flash |
| 12 | Wired remote controller communication error | 1 flash | 2 flashes |
| 22 | Indoor unit capacity error | 2 flashes | 2 flashes |
| 32 | Indoor unit model information / EEPROM abnormality | 3 flashes | 2 flashes |
| 35 | Manual Auto switch error | 3 flashes | 5 flashes |
| 41 | Indoor room thermistor error | 4 flashes | 1 flash |
| 42 | Indoor heat exchanger thermistor error | 4 flashes | 2 flashes |
| 51 | Indoor unit fan motor error | 5 flashes | 1 flash |
| 53 | Drain pump error | 5 flashes | 3 flashes |
| 58 | Intake grille error | 5 flashes | 8 flashes |
| 62 | Outdoor unit model information error | 6 flashes | 2 flashes |
| 63 | Inverter error | 6 flashes | 3 flashes |
| 64 | Active filter error | 6 flashes | 4 flashes |
| 65 | IPM error | 6 flashes | 5 flashes |
| 71 | Discharge thermistor error | 7 flashes | 1 flash |
| 72 | Compressor thermistor error | 7 flashes | 2 flashes |
| 73 | Outdoor heat exchanger thermistor error | 7 flashes | 3 flashes |
| 74 | Outdoor thermistor error | 7 flashes | 4 flashes |
| 76 | 2-way / 3-way valve thermistor error | 7 flashes | 6 flashes |
| 84 | CT error | 8 flashes | 4 flashes |
| 86 | Discharge pressure sensor error | 8 flashes | 6 flashes |
| 94 | Over current error | 9 flashes | 4 flashes |
| 95 | Compressor control error | 9 flashes | 5 flashes |
| 97 | Outdoor unit fan motor error | 9 flashes | 7 flashes |
| 99 | 4-way valve error | 9 flashes | 9 flashes |
| 9A | Expansion valve coil error | 9 flashes | 10 flashes |
| A1 | Discharge temperature error | 10 flashes | 1 flash |
| A3 | Compressor temperature error | 10 flashes | 3 flashes |
3. Diagnostic flow by fault group
Communication – 11 / 12
- Reset power and confirm whether the fault returns.
- Check indoor-to-outdoor communication wiring for loose, removed, open or incorrectly connected conductors.
- Confirm the outdoor supply is approximately AC 198–264 V at L1–L2.
- For serial communication faults, check the forward/reverse serial signal at the outdoor unit and then isolate whether the fault is indoor PCB, outdoor main PCB, fan motor or wiring related.
- For wired remote faults, check the remote controller wiring and the controller supply/communication voltage at the indoor controller PCB.
Capacity / model information – 22 / 32 / 62
- 22: Confirm the total connected indoor-unit capacity is within the permitted combination range.
- 32: Reset power, inspect indoor electrical connectors and wiring, then investigate the indoor controller PCB if the error remains.
- 62: Reset power, inspect outdoor electrical connections and possible electrical noise, then investigate the outdoor main PCB if the fault remains.
Indoor thermistors – 41 / 42
- Inspect the thermistor connector and wiring for disconnection, open circuit or incorrect connection.
- Disconnect the thermistor and compare resistance with the service-manual characteristic table.
- If the thermistor is open or shorted, replace the thermistor and reset power.
- If the thermistor is normal, confirm the controller PCB provides approximately DC 5 V at the thermistor circuit.
Indoor fan – 51
- With power isolated, rotate the fan by hand and check for binding, dropped fan, locked motor or abnormal bearings.
- Check for excessive temperature around the motor and allow it to cool before retesting.
- Check indoor fan motor wiring and winding/circuit condition.
- If the motor checks are normal and the fault remains, investigate the indoor controller PCB.
Drain pump / intake grille – 53 / 58
- 53 Drain pump: Check float-switch operation, connector/wiring, drain hose blockage and drain-pump operation. The fault is detected when the float switch remains ON for more than approximately 3 minutes.
- 58 Intake grille: Check the micro/limit switch operation and wiring. The fault is generated when the micro switch detects open while the compressor is running.
Inverter / active filter / IPM – 63 / 64 / 65
- 63 Inverter: Check for external voltage/noise issues, wiring from the filter PCB to inverter PCB, then investigate inverter PCB, main PCB and filter PCB in the order shown in the service flow.
- 64 Active filter: Check for abnormal supply voltage/noise, loose connectors and the active filter module. The service manual identifies abnormal inverter input DC voltage above approximately 430 V or below approximately 110 V as one detection condition.
- 65 IPM: Check outdoor electrical connectors, outdoor heat exchanger obstruction, outdoor fan operation and compressor condition before replacing the main PCB.
Outdoor thermistors – 71 / 72 / 73 / 74 / 76
For each thermistor fault, use the same basic process: inspect the connector/wiring, disconnect and compare resistance against the specified temperature/resistance table, then verify approximately DC 5 V from the main PCB. Replace the thermistor if open/shorted; investigate the main PCB if the sensor is correct but the PCB supply is absent.
CT / pressure sensor – 84 / 86
- 84 CT: Reset power, inspect outdoor electrical connections and external electrical noise/voltage-drop causes. If the error remains after these checks, investigate the outdoor main PCB.
- 86 Discharge pressure sensor: Check CN92 and pressure-sensor wiring. The fault can be generated when sensor output remains below approximately 0.3 V for 30 seconds or is detected above approximately 5.0 V. Main PCB CN92 pins 1–3 should provide approximately DC 5 V.
Over current / compressor / outdoor fan – 94 / 95 / 97
- 94 Over current: Check outdoor heat exchanger for blockage, outdoor fan operation, ambient temperature and compressor condition.
- 95 Compressor control: Inspect compressor terminal wiring and connections. If wiring is correct, follow the manual sequence through main PCB and compressor checks.
- 97 Outdoor fan: Check mechanical rotation, ambient temperature, fan motor wiring and PCB output. A stalled or abnormally slow fan can trigger the fault.
4-way valve / EEV / temperature protection – 99 / 9A / A1 / A3
- 99 4-way valve: Compare indoor heat-exchanger and room temperature, check indoor thermistors, solenoid coil resistance, four-way valve operation and PCB output.
- 9A EEV coil: Check connector seating, coil wiring, winding resistance and PCB output. Also inspect for abnormal start-up noise and for a mechanically stuck or clogged valve/strainer where relevant.
- A1 Discharge temperature: Check 3-way valve position, EEV/strainer, outdoor fan/heat exchanger, discharge thermistor and refrigerant quantity. The manual identifies protection when discharge pipe temperature reaches approximately 110°C twice within 24 hours.
- A3 Compressor temperature: Follow the same refrigerant-cycle checks using the compressor thermistor. The manual identifies protection when compressor temperature reaches approximately 108°C twice within 24 hours.
4. Troubleshooting when there is no error code
| Symptom | Primary checks |
|---|---|
| Indoor unit – no power | Breaker, removed/open cable, voltage drop/noise, AC 198–264 V supply at outdoor L1–L2, filter PCB fuse and varistor, filter PCB. |
| Outdoor unit – no power | Breaker/cabling, voltage drop/noise, AC 198–264 V supply, main PCB fuse, active filter module, main PCB. |
| No operation – power is ON | Indoor/outdoor installation condition, correct indoor model/remote compatibility, communication wiring, external voltage/noise, remote controller and controller PCB. |
| No cooling / no heating | Indoor fan and filters, blocked airflow, heat exchanger, outdoor operation, outdoor airflow, valve open, capacity/room size, piping/communication, refrigerant cycle, strainer, EEV and compressor. |
| Abnormal noise | Indoor/outdoor mounting, vibration, fan guard, loose or damaged fan, piping contact noise and compressor noise. |
| Water leaking | Indoor mounting/level, drain hose connections, drain trap, blocked drain hose, drain pump/fan and refrigerant gas pressure if water is spitting from the outlet. |
| Too warm / too cool | Building insulation function setting, selected temperature-sensing location, remote temperature indication, Function 42/48 sensor selection, remote-controller location and temperature-correction function settings. |
5. Key service test values
| Component / test | Reference value | Action if abnormal |
|---|---|---|
| Outdoor supply | AC 198–264 V at L1–L2 | Investigate supply, connections and voltage-drop/noise causes. |
| Compressor winding | Approximately 0.642 Ω ±8% at 20°C between phases | Open/infinite or abnormal winding resistance indicates compressor fault. |
| EEV coil | 46 Ω ±4 Ω at 20°C for each specified winding pair | Replace EEV coil if winding resistance is abnormal. |
| EEV PCB output | Approximately DC 12 V pulse/output check at specified connector | If output is absent after wiring/coil checks, investigate main PCB. |
| Pressure sensor supply | DC 5 V at CN92 pins 1–3 | If 5 V supply is absent with sensor disconnected, investigate main PCB. |
| Pressure sensor characteristic | Approx. 0.5 V at 0 MPa rising linearly to approx. 4.5 V at 5.0 MPa | Replace sensor if output is inconsistent with applied pressure. |
| Outdoor fan PCB output | Red–Black: DC 260–400 V; White–Black: DC 15 ±1.5 V | If fan motor checks normal but PCB output is incorrect, investigate main PCB. |
| Fan motor short check | Manual states below 300 kΩ indicates short-circuit condition | Indoor: replace fan motor and controller PCB. Outdoor: replace fan motor and main PCB. |
6. Main PCB replacement caution
Important: The service manual warns that if the outdoor main PCB is replaced without completing the required service-level / check-run procedure, normal operation may not be possible. After replacement, perform CHECK RUN, review the result and correct any detected terminal/wiring mismatch before returning the system to service.
Source: LBLA36/45 Multi Troubleshooting manual. Use the applicable installation and service manual for the exact model and production revision before replacing components.