ART / AOT Single Phase Duct R410A Inverter Units

Freshdesk Solution Article - Technical Support Step-by-Step Phone Instructions
Safety position: This guide is for technical support coaching of licensed and competent service personnel only. Before live testing, confirm the person onsite is authorised, has PPE and suitable test equipment. For power-off tests, isolate supply and wait before touching electrical components. Do not instruct a customer or unqualified person to remove covers or perform electrical tests.

1. Document scope

AreaDetails
Indoor modelsAR*18LUAD, AR*24LUAN, AR*30LUAN, AR*36LUAN, AR*45LUAN, AR*45LUAK, AR*54LUAK
Outdoor modelsAO*18LMAKL, AO*24LMAKL, AO*30LMAWL, AO*36LMAWL, AO*45LJBYL, AO*45LJAYL, AO*54LJAYL
System typeR410A single phase inverter duct systems. Smaller models use single outdoor fan; AR*45/54 class uses upper/lower outdoor fans.
Core electrical focusOutdoor L-N supply AC198-264 V, reverse serial signal at outdoor terminal 1-3 AC70-130 V, remote controller DC12 V supply at CN17/CN6.
PurposeFreshdesk-ready call guide with linked flowcharts, component tests, expected readings and ticket evidence requirements.

2. Error code quick reference

CodeManual fault descriptionPhone support action / linked test
E:00Communication error - indoor unit remote controlRemote communication / 3 wire remote check
E:01Communication error - serial reverse transferSerial communication split flow
E:02 / E:03Room temperature sensor open / shortIndoor thermistor testing
E:04 / E:05Indoor heat exchanger sensor open / shortIndoor heat exchanger thermistor
E:06Outdoor heat exchanger temperature sensor errorOutdoor thermistor testing
E:09Water drain abnormalDrain / float switch
E:0AOutdoor temperature sensor errorOutdoor thermistor testing
E:0COutdoor discharge pipe temperature sensor errorDischarge thermistor
E:0F / E:16Pressure switch errorPressure switch
E:11Indoor EEPROM abnormal / Model No.Indoor EEPROM / PCB
E:12Indoor fan motor abnormalIndoor fan motor
E:13 / E:1bOutdoor unit fan motor errorOutdoor fan flow
E:14Outdoor communication signal error / forward transfer signal errorCommunication flow
E:15Compressor temperature sensor errorCompressor thermistor
E:17IPM errorIPM flow
E:18CT errorCT/current sensor
E:19Active filter module errorActive filter module
E:1ACompressor rotor location cannot detect / permanent stopCompressor rotor flow

3. Quick map

Symptom / error familyMost likely areaJump to
Remote blank / E:00Remote terminal wiring, CN17/CN6 remote supply, controller PCB, remote controller3 wire remote check
E:01 / E:14 communicationTerminal 1-2-3 wiring, L-N supply, external noise, active filter, main PCBCommunication split flow
E:02-E:06 / E:0A / E:0C / E:15Thermistor connector, resistance and PCB 5 V supplyThermistors
E:12Indoor fan rotation, capacitor, motor, controller/power PCBIndoor fan
E:13 / E:1bOutdoor fan rotation, motor resistance, output voltage, main PCBOutdoor fan
E:17 / E:18 / E:19IPM, CT/current, active filter, main PCB, compressor loadIPM / Active filter
E:1A / compressor start-up errorCompressor noise, harness, winding resistance, main PCBCompressor rotor
High discharge / compressor temperature trips3-way valve, EEV, strainer, fan/heat exchanger, refrigerant chargeDischarge/compressor temp

4. Outdoor LED and self-diagnosis guidance

Display itemFreshdesk instruction
Remote self-diagnosisWhen E:EE flashes, stop operation and hold the set temperature buttons together for 5 seconds or more. The remote displays the error code. Stop the display by the same buttons or no key input for 20 seconds.
Error historyStop operation. Press set temperature buttons and START/STOP together for 5 seconds, then press START/STOP and use set temperature buttons to select history number. Up to 16 memorised errors can be reviewed.
Outdoor LED - AO18/24Forward transfer 1 flash, outdoor heat exchanger 2 blinks, outdoor temperature 3 blinks, discharge pipe 4 blinks, pressure switch 8 blinks, IPM 10 blinks, CT 11 blinks, compressor rotor 12 blinks, compressor start-up 13 blinks.
Outdoor LED - AO30/36/45/54Forward transfer 1 flash, outdoor heat exchanger 2 blinks, outdoor temperature 3 blinks, discharge pipe 4 blinks, heat sink 8 blinks, pressure switch 9 blinks, IPM 10 blinks, CT 11 blinks, compressor rotor 12 blinks, compressor start-up 13 blinks, upper fan 15 blinks, lower fan 16 blinks.
Normal LED operationNormal operation is continuously lit; protected operation is 5 sec ON / 1 sec OFF; pump down is 1 sec ON / 1 sec OFF.

5. GREAT-style linked flowcharts

E:00 remote communication flow - Indoor unit

Indoor unit cannot receive wired remote signal more than 10 seconds after power ON or more than 1 minute during normal operation
↓
Power off and check remote control terminal connection between remote and indoor unit
↓
Check cable for open circuit, wrong terminal, loose conductor or damaged joint
↓
Check DC12 V remote supply at indoor controller PCB: AR18L = CN17, AR24L-54L = CN6
↓
Complete the 3 wire Y1/Y2/Y3 remote signal test
↓
DC12 V present, no remote signal
Remote controller is likely defective after wiring is confirmed.
DC0 V at PCB supply
Controller PCB likely defective after remote and wiring are checked again.
Wiring issue found
Repair terminal/wiring, reset power and retest.
Important: Do not approve an indoor controller PCB until the remote cable, terminal order and DC12 V supply have been proven.

3 wire remote controller communication check flow

E:00 indoor remote control communication error / remote signal check
↓
↓
↓
Y1-Y3 is 12 VDC
no less than 11.4 VDC
Remote has controller power. Continue to Y2 signal checks.
Y1-Y3 is 0 VDC
Check indoor controller PCB remote supply connector. AR18L uses CN17. AR24L-54L use CN6. Expected DC12 V.
Y1-Y3 below 11.4 VDC
Check cable length, poor joints, wrong polarity, damaged controller cable or loaded indoor PCB supply.
↓
Remove Y2 from the remote, keep conductor safe, then test between remote terminal Y2 and Y3
↓
Remote Y2-Y3 pulse present
Expected fluctuating 7-11 / 7-12 VDC. Remote is producing signal; continue to field cable signal check.
No remote Y2-Y3 pulse
Remote controller likely defective after confirming 12 VDC supply is correct.
↓
Test between disconnected Y2 wire going to indoor unit and Y3 COM
↓
Field Y2-Y3 pulse present
Indoor PCB is returning signal. Reconnect Y2. If communication still fails, inspect terminals, shielding/noise and controller condition.
No field Y2 pulse
Check open cable / short to COM / incorrect terminal. If wiring is sound, suspect indoor controller PCB.
Record in ticket: Y1-Y3 supply voltage, remote Y2-Y3 pulse result, disconnected field Y2-to-Y3 pulse result, cable condition and CN17/CN6 remote supply voltage.

E:01 communication split flow - ART / AR single phase duct

E:01 serial reverse transfer error / indoor cannot receive serial signal from outdoor
↓
↓
↓
Reverse transfer / outdoor signal path
Is AC70-130 V signal present at terminal 1-3?
YES
Outdoor reverse signal is present. Check field cable, noise, earthing and indoor receiving side.
NO
Check active filter module first. If active filter module is abnormal, replace it. If normal, main PCB becomes suspect.
Forward transfer / outdoor receiving path
Outdoor LED forward signal error present?
YES
Check field cable, terminal 1/2/3, noise and outdoor PCB signal receiving side.
NO
Return to remote/indoor checks if symptom is E:00 or no remote communication.
Important split: E:01 reverse transfer uses outdoor terminal 1-3 with AC70-130 V. Confirm L-N supply, field wiring, external noise/earthing and active filter before main PCB approval.

E:17 IPM / overcurrent protection flow - Outdoor unit

IPM error / abnormal current protection
↓
Check outdoor unit electrical component connections: removed connector, loose terminal, incorrect connection or open cable
↓
Check outdoor fan operation, heat exchanger obstruction and ambient recirculation
↓
Check outdoor fan motor and fan rotation by hand
↓
Check compressor harness and winding resistance
↓
If checks do not improve symptom, main PCB / transistor PCB sequence becomes suspect
↓
Connector issue found
Correct removed connector, loose terminal or mis-wiring and reset power.
Airflow or fan fault
Correct airflow/coil/fan issue before PCB approval.
Compressor abnormal
Escalate as compressor fault after values are recorded.
All checks pass
Escalate PCB/IPM decision only after connections, fans and compressor are documented.
Important: E:17/IPM should not be treated as board-only until electrical connections, outdoor fan/heat exchanger, compressor and IPM checks are documented.

E:1A compressor rotor location flow - Outdoor unit

Compressor rotor location cannot detect / permanent stop
↓
Turn unit on and confirm whether abnormal compressor noise is present
↓
Isolate supply and visually inspect compressor harness cable, compressor terminals and main PCB connections
↓
Check compressor winding resistance U-V, V-W and U-W and record values
↓
If connection and winding checks are normal but error remains, main PCB becomes suspect
↓
If main PCB does not improve symptom, compressor becomes suspect
↓
Abnormal compressor noise present
Record noise evidence and consider compressor fault after wiring and winding checks.
Harness burnt, loose, open or miswired
Repair or replace affected harness or terminal connection, then reset power and retest.
Compressor winding abnormal
Escalate as compressor fault after values are recorded.
All checks pass
Escalate main PCB first, then compressor if fault remains after PCB sequence.
Important: For E:1A, physically inspect compressor harness and terminals. Do not replace compressor or PCB without recording compressor winding resistance and harness condition.

E:13 / E:1b outdoor fan motor flow

Outdoor fan motor error / upper-lower outdoor fan error
↓
Power off and rotate fan by hand. Check if fan is caught, locked, dropped or bearing is abnormal
↓
Check high ambient temperature or surrounding heat source around the motor
↓
Check outdoor fan motor using component test procedure
↓
Check output voltage from main PCB at fan connector where safe to do live test
↓
If fan motor abnormal, replace fan motor and main PCB as required by test result
↓
Fan/bearing locked
Replace fan or bearing assembly and retest.
Motor abnormal
Replace outdoor fan motor. Where fan motor shorts, protect PCB decision as required.
PCB output abnormal
Replace main PCB after fan motor is proven normal.
Ambient issue
Correct heat source/airflow first and restart operation.
Important: For AO30/36/45/54, identify whether the error is upper or lower fan by LED pattern before approving parts.

High discharge / compressor temperature protection flow

Discharge pipe or compressor temperature protection / refrigerant system condition
↓
Primary check: suspect refrigerant leak / insufficient refrigerant first
↓
Check 3-way valve is fully open
↓
Check EEV operation / coil resistance, capillary / strainer restriction and temperature difference across strainer
↓
Check outdoor fan operation and heat exchanger for foreign matter / blocked fins / recirculation
↓
Check discharge or compressor temperature thermistor value and DC 5 V PCB supply
↓
Check refrigerant amount / leak test and weigh charge where required
↓
Leak or insufficient refrigerant found
Repair leak, pressure test, evacuate and weigh in charge as required.
3-way valve closed / not fully open
Open valve fully and re-test operation.
EEV / strainer issue
Confirm coil resistance, start-up noise, operation and temperature difference across restriction.
Thermistor abnormal
Replace thermistor or repair harness only after value is confirmed against temperature.
All checks pass but fault remains
Main PCB/inverter control becomes suspect after refrigerant, valves, EEV, airflow and thermistor are proven.
Important: Treat discharge/compressor temperature faults as refrigerant and system-condition faults first. Do not approve PCB until refrigerant, valves, EEV/strainer, airflow and thermistor evidence is recorded.

6. Step-by-step phone support SOPs

SOP 1 - Intake and safety gate

  1. Confirm caller name, company, site address, indoor model/serial and outdoor model/serial.
  2. Confirm exact complaint: error code, operating mode, when it occurs and whether it is repeatable.
  3. Confirm safety: no burning smell, water ingress, damaged wiring, repeated breaker trips or refrigerant odour.
  4. Confirm tools: multimeter with AC/DC volts, resistance and diode test.
  5. Decision point: if caller is not qualified or cannot identify terminals safely, stop at non-invasive checks and arrange authorised attendance.

SOP 2 - E:01 serial communication

  1. Reset power and confirm if E:01 returns.
  2. Check external causes such as poor earth, noise or equipment causing harmonic wave near power cable.
  3. Check interconnect wiring between indoor and outdoor and check control-unit connections.
  4. Check outdoor supply: expected AC198-264 V at outdoor terminal L-N.
  5. Reverse transfer signal: check outdoor terminal 1-3. Expected swing AC70-130 V.
  6. If reverse transfer signal is abnormal, check active filter module. If active filter is abnormal, replace it. If active filter is normal, main PCB becomes suspect.

SOP 3 - Outdoor forward transfer / E:14

  1. Confirm outdoor LED pattern and remote error history.
  2. Check terminal 1/2/3 wiring and field cable continuity.
  3. Check for open cable, poor connection, crossed conductors and noise/earthing issues.
  4. If wiring and site conditions are proven normal, main PCB receiving path becomes suspect.

SOP 4 - 3 wire remote signal test

  1. At the rear of the wall controller, confirm Y1 = 12 V/red, Y2 = signal/white, Y3 = COM/black.
  2. Measure Y1 to Y3: expected 12 VDC, no less than 11.4 VDC.
  3. Manual PCB supply reference: AR18L uses CN17; AR24L to AR54L use CN6. Expected remote supply is DC12 V.
  4. Remove Y2 from the remote. Measure between remote terminal Y2 and Y3: expected fluctuating 7-11 / 7-12 VDC pulse.
  5. Measure between the disconnected Y2 wire going to the indoor unit and Y3: expected fluctuating 7-11 / 7-12 VDC pulse.
  6. If no 12 V supply, check indoor PCB remote power supply. If remote has supply but no Y2 pulse, suspect remote controller. If field Y2 has no return pulse, check cable and indoor controller PCB.

SOP 5 - Thermistor testing

  1. Isolate power. Check connector is not loose, removed, miswired or open.
  2. Disconnect thermistor and measure resistance out of circuit. Compare to actual bulb temperature.
  3. Indoor room thermistor rough values: 0C 33.6 kΩ, 5C 25.9 kΩ, 10C 20.2 kΩ, 15C 15.8 kΩ, 20C 12.5 kΩ, 25C 10.0 kΩ, 30C 8.04 kΩ, 35C 6.51 kΩ, 40C 5.30 kΩ, 45C 4.35 kΩ, 50C 3.59 kΩ.
  4. Indoor heat exchanger thermistor rough values: 0C 176 kΩ, 5C 134 kΩ, 10C 103 kΩ, 15C 80.3 kΩ, 20C 62.9 kΩ, 25C 49.7 kΩ, 30C 39.6 kΩ, 35C 31.7 kΩ, 40C 25.6 kΩ, 45C 20.8 kΩ, 50C 17.1 kΩ.
  5. Outdoor heat exchanger thermistor rough values: -10C 27.5 kΩ, -5C 20.9 kΩ, 0C 16.1 kΩ, 5C 12.4 kΩ, 10C 9.73 kΩ, 15C 7.67 kΩ, 20C 6.10 kΩ, 25C 4.89 kΩ, 30C 3.95 kΩ.
  6. Outdoor temperature thermistor rough values: -20C 115 kΩ, -10C 62.3 kΩ, -5C 46.6 kΩ, 0C 35.2 kΩ, 5C 26.9 kΩ, 10C 20.7 kΩ, 15C 16.1 kΩ, 20C 12.6 kΩ, 30C 7.97 kΩ, 40C 5.18 kΩ, 50C 3.45 kΩ, 60C 2.36 kΩ, 70C 1.65 kΩ.
  7. Discharge thermistor rough values: 0C 176 kΩ, 20C 26.9 kΩ, 30C 12.5 kΩ, 60C 3.43 kΩ, 100C 1.98 kΩ, 120C 1.21 kΩ, 180C 0.51 kΩ.
  8. With thermistor removed, check PCB supply at thermistor connector: expected DC5.0 V.

SOP 6 - Indoor fan motor testing

  1. Power off. Rotate fan by hand and check for obstruction, bearing lock, dropped fan or casing contact.
  2. Check fan motor capacitor where fitted and inspect wiring to power PCB / controller PCB.
  3. Check ambient temperature around the motor and confirm no external heat source is affecting it.
  4. Check indoor fan motor using the component test method from service training.
  5. Record fan rotation, motor reading, connector condition and PCB decision.

SOP 7 - Outdoor fan motor testing

  1. Power off. Rotate fan by hand and check obstruction, bearing lock, fan guard contact or damaged fan.
  2. For AR45/54 class, identify upper or lower fan from LED blink pattern and check the correct fan.
  3. Check ambient temperature around the motor and confirm no external heat source is affecting it.
  4. Check outdoor fan motor using service parts / component test method.
  5. Live output reference varies by model; only test live output when qualified and safe.
  6. On communication faults, abnormal fan motor or loading can affect PCB operation; record fan condition before PCB approval.

SOP 8 - EEV and strainer testing

  1. Check EEV connector for loose connector or open cable.
  2. Remove connector and check EEV coil resistance. Common service training value: Yellow-Red, Orange-Red, Blue-Red, White-Red = 46 Ω ±4 Ω at 20C.
  3. Remove connector and check PCB drive voltage: expected DC12 V.
  4. Turn on power and listen/feel for EEV start-up operation noise.
  5. Check opening/closing effect by temperature difference. Closed valve creates inlet/outlet temperature difference; open valve has no temperature difference.
  6. Check strainer. A temperature difference across the strainer suggests internal clogging.

SOP 9 - Compressor testing

  1. Check compressor terminal connection and main PCB connection for loose or incorrect wiring.
  2. Check winding resistance between U-V, V-W and U-W and record all three values.
  3. Manual resistance values at 20C: AR18/24 = 1.41 Ω; AR30/36 = 0.88 Ω; AR45/54 = 0.188 Ω.
  4. If resistance is 0 Ω or infinite, replace compressor.
  5. If compressor does not start or stops soon, check gas pipe valve open, refrigerant leak and strainer clogging before compressor approval.
  6. If connection and winding resistance do not improve symptom, follow manual sequence for main PCB and then compressor.

SOP 10 - Active filter module

  1. Use this for E:01 reverse transfer abnormal signal and E:19 active filter module error.
  2. Check external causes first: voltage drop, momentary power failure, defective contact, noise and grounding.
  3. Check connector condition between outdoor main PCB and filter/active filter section.
  4. Check active filter module using the service parts method.
  5. If active filter module is abnormal, replace it. If active filter is normal and E:01 remains, main PCB becomes suspect.

SOP 11 - IPM / CT / main PCB

  1. Use this for E:17 IPM error, E:18 CT error and compressor-related permanent stop faults.
  2. Confirm L-N supply is within range before board approval.
  3. Inspect transistor/IPM/main PCB connections and harnesses for loose connectors, corrosion, open cable or burn marks.
  4. Check compressor winding and outdoor fan motor loading before recommending PCB replacement.
  5. Attach photos and readings to ticket before board approval.

SOP 12 - Pressure switch

  1. Check pressure switch connector and wiring condition.
  2. Confirm operating conditions, outdoor airflow and coil condition.
  3. Check refrigerant circuit for restriction or overpressure causes before replacing pressure switch.
  4. Record actual pressure, mode, fan operation, coil condition and pipe temperatures.

SOP 13 - Drain / float switch

  1. Check drain pan, float switch and any blockage by dust.
  2. Remove float switch and check ON/OFF switching operation by meter.
  3. Check connector and shorted / pinched wire.
  4. Check drain hose for clogging, traps or poor fall.
  5. If all checks are normal and drainage error remains, controller PCB becomes suspect.

SOP 14 - Indoor EEPROM / model abnormal

  1. Reset power and confirm if E:11 returns.
  2. Check indoor controller PCB connectors for loose connector or incorrect wiring.
  3. Check PCB for damage, corrosion or water ingress.
  4. Check external cause such as poor earth or harmonic noise near power cable.
  5. If checks do not improve symptom, controller PCB becomes suspect.

SOP 15 - Current / CT error

  1. Reset power and confirm if CT error returns.
  2. Check external causes: voltage drop, momentary open circuit, noise and grounding.
  3. Check outdoor electrical component connectors, terminal tightness, miswiring and open cables.
  4. Check compressor operation and current draw where safe to do so.
  5. If checks do not improve symptom, main PCB / CT circuit becomes suspect.

7. R410A refrigerant service notes

RequirementInstruction
ToolsUse R410A-rated manifold, charge hoses, vacuum equipment, electronic scale and HFC leak detector.
ChargingCharge from liquid phase. Do not charge from gas phase because R410A is mixed refrigerant.
Moisture / contaminationKeep moisture and contamination out of the system. Use proper vacuum drying and avoid reverse oil flow from vacuum pump.
PipeworkUse R410A-rated pipe and correct flare tools / torque. Do not reuse unsuitable R22 pipework.

8. Ticket evidence checklist

Evidence requiredDetails to record
Model and serialIndoor and outdoor model/serial, controller type and exact error display.
Safety and site conditionWho is onsite, licence/competency confirmation, power isolation status, access limitations, water ingress/burning smell/short circuit risk.
Remote / LED evidenceRemote error code/history, outdoor LED blink pattern, whether error occurs after reset or during operation.
Electrical readingsL-N supply voltage, terminal 1-3 communication reading, remote Y1/Y2/Y3 readings, CN17/CN6 remote supply, fan motor checks, PCB 5 V / 12 V checks.
Component readingsThermistor kΩ and measured temperature, EEV coil Ω, compressor winding Ω, active filter/IPM observations.
Refrigeration evidenceValve positions, operating mode, ambient, fan operation, coil condition, pressures, leak test, strainer temperature difference, weighed charge details.
Approval decisionState what has been proven before recommending remote controller, controller PCB, fan motor, thermistor, compressor, active filter module, main PCB or IPM/transistor PCB.