ASTH30/34KNTA - AOTH30/34KNTA Single Phase Wall Hung R32 Split Systems
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 at least 5 minutes before touching electrical components. R32 is flammable refrigerant, so leak detection, ventilation and ignition-source controls must be followed before refrigerant circuit work.
Controller note: This wall hung article does not include a 3 wire wall-controller communication flow. The standard controller is wireless; optional wired remote control uses a non-polar 2-wire communication kit, not the older 3 wire Y1/Y2/Y3 process.
Document scopeError tableQuick mapLED / memoryFlowchartsLED identificationE:11 communicationE:51 indoor fanE:97 outdoor fanE:63 inverterE:64 PFCE:65 IPME:94 trip/overcurrentE:95 compressorE:A1 discharge tempE:A3 compressor tempIntakeLED memory SOPCommunication SOPIndoor fanOutdoor fanMain PCB testsIPM / diodeThermistorsEEVCompressorPressure switchTicket checklist
1. Document scope
| Area | Details |
|---|---|
| Indoor models | ASTH30KNTA, ASTH34KNTA |
| Outdoor models | AOTH30KNTA, AOTH34KNTA |
| Refrigerant / supply | R32 inverter heat pump. Outdoor unit power supply 220-240 V, 50 Hz, available voltage range 198-264 V. |
| Capacity / refrigerant charge | ASTH30/AOTH30: 8.5 kW cooling, 9.0 kW heating, R32 charge 1,700 g. ASTH34/AOTH34: 9.5 kW cooling, 10.3 kW heating, R32 charge 2,300 g. |
| Main service references | Indoor main PCB, indicator PCB, DC indoor fan motor, outdoor main PCB, inverter PCB, DC outdoor fan motor, EEV, pressure switch on AOTH34, thermistor circuits and compressor winding values. |
2. Error code quick reference
| Code | Indoor LED pattern | Fault description | Linked support flow |
|---|---|---|---|
| E:11 | Operation 1 / Timer 1 / Economy continuous | Serial communication error - reverse transfer outdoor or forward transfer indoor | E:11 communication |
| E:12 | Operation 1 / Timer 2 / Economy continuous | Wired remote controller communication error if optional 2-wire remote kit fitted | Optional 2-wire remote note |
| E:18 | Operation 1 / Timer 8 / Economy continuous | External communication error | External communication |
| E:22 | Operation 2 / Timer 2 / Economy continuous | Indoor unit capacity error | Capacity / combination |
| E:23 | Operation 2 / Timer 3 / Economy continuous | Combination error | Capacity / combination |
| E:32 | Operation 3 / Timer 2 / Economy continuous | Indoor unit main PCB error | Main PCB tests |
| E:33 | Operation 3 / Timer 3 / Economy continuous | Indoor unit motor electricity consumption detection error | Indoor fan flow |
| E:35 | Operation 3 / Timer 5 / Economy continuous | MANUAL AUTO button error | Manual auto button |
| E:39 | Operation 3 / Timer 9 / Economy continuous | Indoor unit power supply error for fan motor | Indoor fan flow |
| E:41 | Operation 4 / Timer 1 / Economy continuous | Room temperature sensor error | Thermistors |
| E:42 | Operation 4 / Timer 2 / Economy continuous | Indoor heat exchanger sensor error | Thermistors |
| E:51 | Operation 5 / Timer 1 / Economy continuous | Indoor unit fan motor error | Indoor fan flow |
| E:62 | Operation 6 / Timer 2 / Economy continuous | Outdoor unit main PCB error | Outdoor PCB |
| E:63 | Operation 6 / Timer 3 / Economy continuous | Inverter error | Inverter flow |
| E:64 | Operation 6 / Timer 4 / Economy continuous | PFC circuit error | PFC flow |
| E:65 | Operation 6 / Timer 5 / Economy continuous | IPM error / trip terminal L error | IPM flow |
| E:71 | Operation 7 / Timer 1 / Economy continuous | Discharge thermistor error | Thermistors |
| E:72 | Operation 7 / Timer 2 / Economy continuous | Compressor thermistor error | Thermistors |
| E:73 | Operation 7 / Timer 3 / Economy continuous | Outdoor heat exchanger / middle / outlet thermistor error | Thermistors |
| E:74 | Operation 7 / Timer 4 / Economy continuous | Outdoor temperature thermistor error | Thermistors |
| E:77 | Operation 7 / Timer 7 / Economy continuous | Heat sink thermistor error | Heat sink thermistor |
| E:84 | Operation 8 / Timer 4 / Economy continuous | Current sensor error | Current sensor |
| E:86 | Operation 8 / Timer 6 / Economy continuous | High pressure switch error | Pressure switch |
| E:94 | Operation 9 / Timer 4 / Economy continuous | Trip detection / over current error | Trip / overcurrent |
| E:95 | Operation 9 / Timer 5 / Economy continuous | Compressor motor control error | Compressor control |
| E:97 | Operation 9 / Timer 7 / Economy continuous | Outdoor unit fan motor error | Outdoor fan flow |
| E:99 | Operation 9 / Timer 9 / Economy continuous | 4-way valve error | 4-way valve |
| E:A1 | Operation 10 / Timer 1 / Economy continuous | Discharge temperature error | Discharge temp |
| E:A3 | Operation 10 / Timer 3 / Economy continuous | Compressor temperature error | Compressor temp |
| E:AC | Operation 10 / Timer 12 / Economy continuous | Heat sink temperature error | Heat sink thermistor |
3. Quick map
| Symptom / error family | Most likely area | Jump to |
|---|---|---|
| LEDs flashing but code uncertain | Operation / Timer / Economy flash pattern, error memory procedure | LED identification |
| E:11 communication | Terminal 1-2-3 wiring, L-N supply, external noise, fan motor loading, indoor/outdoor PCB | Communication flow |
| E:33/E:39/E:51 | Indoor crossflow fan, DC indoor fan motor, CN5, indoor main PCB | Indoor fan |
| E:97 | Outdoor propeller fan, P650 DC fan motor, inverter PCB output, fan loading | Outdoor fan |
| E:63/E:64/E:65/E:94 | Inverter PCB, PFC, IPM, fuses, diode bridge, compressor and fan motor loading | Inverter / IPM |
| E:95 | Compressor U/V/W resistance, harness, IPM / inverter PCB | Compressor control |
| E:A1/E:A3 | Refrigerant leak/undercharge, 3-way valves, EEV/strainer, fan/coil, discharge or compressor thermistor | Discharge temp / Compressor temp |
| Thermistor errors | Connector, thermistor resistance, PCB 5 V supply | Thermistors |
| No power | Outdoor L/N supply, fuses F100/F101/F102/F103, indoor terminal supply, main PCB | Main PCB tests |
4. Indoor LED and error memory guidance
| Item | Freshdesk instruction |
|---|---|
| Error memory | Stop operation, disconnect power, reconnect power, then during the 3 minute ST period start operation and press TEST RUN on the remote, or press MANUAL AUTO for 10 seconds or more. The display window is about 2 minutes 20 seconds. |
| Erase memory | Manual erase is by pressing MANUAL AUTO while error memory is being displayed. Automatic erase occurs after normal operation without error for 2 hours or more, excluding fan mode. |
| Outdoor display | If the outdoor ERROR LED blinks, press ENTER once on the outdoor unit to display the error code by LED pattern. |
| Evidence | Record indoor flash pattern, outdoor LED pattern, whether the error occurred at power-on or during operation, and whether the fault returns after reset. |
5. GREAT-style linked flowcharts
Indoor unit LED display flow - ASTH30/34KNTA
Use Operation, Timer and Economy LEDs to confirm the active fault before component testing
↓
Turn unit on with the wireless remote if no error is showing. Errors are stored in indoor PCB memory and can be displayed during the 3 minute ST period after power is restored.
↓
Record the indoor LED pattern: Operation green flash count, Timer orange flash count and Economy green continuous/other state.
↓
Cross-check the wired remote display number if fitted as an optional 2-wire remote system, but do not use the 3-wire remote controller process.
↓
Valid error code
Map the flash pattern to the error table and jump to the linked flowchart/SOP.
Status indication
Defrost, filter, demand response, timer issue or test run status may not be a component fault.
No code visible
Use error memory procedure or ask for a short LED video before parts are approved.
Record in ticket: model, serial, Operation flash count, Timer flash count, Economy state, error memory result and whether the code returns after reset.
E:11 communication split flow - ASTH30/34KNTA
Serial reverse or forward transfer communication error
↓
↓
↓
Reverse transfer / outdoor signal path
Is AC90-270 V signal present at terminal 1-3?
YES
Outdoor reverse signal is present. Check field cable, noise, earth and indoor receiving side.
NO
Check outdoor fan motor first. If outdoor fan motor is abnormal, replace fan motor and main PCB. If normal, main PCB is suspect.
Forward transfer / indoor signal path
Is AC30-130 V signal present at terminal 2-3?
YES
Indoor forward signal is present. Continue cable/noise/receiving side checks.
NO
Check indoor fan motor. If abnormal, replace indoor fan motor and main PCB. If normal, main PCB is suspect.
Important split: Reverse transfer uses outdoor terminal 1-3 with AC90-270 V. Forward transfer uses outdoor terminal 2-3 with AC30-130 V. Do not approve a PCB until wiring, supply, external noise/earth and fan motor loading are documented.
E:51 / E:33 / E:39 indoor fan motor flow - Indoor unit
Indoor DC fan motor error or fan power/consumption detection error
↓
Confirm LED pattern and whether fault occurs immediately or after fan tries to start
↓
Power off and rotate crossflow fan by hand. Check fan barrel, bearing, motor cover, casing contact and obstruction
↓
Check ambient temperature around motor and any external heat source
↓
Check indoor fan motor CN5: Vm red, GND black, Vcc white, Vsp yellow, FG blue
↓
Use component testing method. If fan motor is abnormal, replace indoor fan motor and assess main PCB. If fan checks OK, indoor main PCB becomes suspect
↓
Fan locked / bearing abnormal
Replace fan/bearing/correct obstruction and retest before PCB approval.
Fan motor abnormal
Replace indoor DC fan motor and record CN5/diode test results.
PCB supply missing
Indoor main PCB becomes suspect after motor and harness are proven.
Overheat condition
Remove heat source and restart operation once temperature normalises.
Important: DC brushless fan motors have internal electronics. Do not disconnect with power applied, and avoid relying on resistance only where diode testing is specified.
E:97 outdoor fan motor flow - Outdoor unit
Outdoor DC fan motor error
↓
Power off. Rotate propeller fan by hand and check obstruction, bearing lock, fan guard contact or weather damage
↓
Check ambient temperature around outdoor fan motor
↓
Check P650 DC fan motor connector: red Vm, black GND, white Vcc, yellow Vsp, brown FG
↓
Power off test: circuit-test Vm and GND. If short-circuited below 300 kΩ, replace outdoor fan motor and main PCB
↓
Power on test only if safe: check high voltage DC and 15 VDC control supply at inverter PCB side
↓
Fan/bearing issue
Clear obstruction or replace fan assembly before electrical approval.
Vm-GND below 300 kΩ
Replace outdoor fan motor and main PCB. Record resistance/diode result.
15 V / high DC missing
Inverter/main PCB output becomes suspect after input supply is proven.
Motor tests OK
Continue to inverter/main PCB and communication checks before approving parts.
Important: The manual states that if outdoor fan Vm-GND is short-circuited below 300 kΩ, replace outdoor fan motor and main PCB.
E:63 inverter error flow - Outdoor unit
Inverter PCB error or main-inverter communication/power issue
↓
Reset power and confirm if E:63 returns
↓
Check L-N supply at outdoor unit and confirm AC198-264 V
↓
Inspect main PCB to inverter PCB harnesses: P660/P662, P661/P663 and P350/P351
↓
Check fuses and DC bus / inverter power paths after isolating safely
↓
If wiring, supply and fuses are proven, inverter PCB or main PCB becomes suspect
↓
Supply issue
Correct supply / neutral / earth before parts are approved.
Connector issue
Repair loose/open/miswired connector and reset.
Fuse/DC bus abnormal
Record fuse and DC readings before PCB recommendation.
All checks pass
Escalate inverter PCB / main PCB sequence with evidence.
Important: Inverter faults require supply, connector and load checks before replacing inverter or main PCB.
E:64 PFC circuit error flow - Outdoor unit
PFC circuit protection / power factor correction fault
↓
Confirm L-N supply and check for temporary voltage drop, open circuit or incorrect grounding
↓
Check noise/harmonic source near power cable
↓
Inspect power supply wiring, fuses and main PCB to inverter PCB harnesses
↓
Check diode bridge / PFC path using power-off diode tests where accessible
↓
If checks do not improve symptom, follow PCB sequence
↓
External supply/noise
Correct supply, earthing or harmonic source and retest.
Wiring/fuse issue
Repair connector/fuse issue and record before reset.
PFC/diode abnormal
Escalate PCB/PFC decision with readings.
All checks normal
Main/inverter PCB becomes suspect after evidence is complete.
Important: PFC errors are supply-sensitive. Always document supply quality, earth/noise checks and power-off diode/fuse tests.
E:65 IPM / trip terminal L flow - Outdoor unit
Abnormal current / IPM protection
↓
Confirm whether fault occurs on compressor start or during operation
↓
Check L-N supply, grounding, noise and connector condition
↓
Check outdoor fan operation and heat exchanger condition
↓
Check compressor harness and U-V, V-W, U-W winding resistance
↓
Check IPM diode paths and inverter PCB outputs
↓
Supply/noise issue
Correct supply/earth/noise and retest.
Fan/airflow issue
Correct fan, coil or recirculation before PCB approval.
Compressor abnormal
Escalate compressor after all winding values are recorded.
IPM abnormal
Escalate inverter/main PCB after compressor is proven.
Important: Do not treat E:65 as board-only until supply, airflow/fan, compressor and IPM evidence is recorded.
E:94 trip detection / over current flow - Outdoor unit
Trip detection or over current protection
↓
Check outdoor fan operation, outdoor heat exchanger, air passages and ambient temperature
↓
Check whether discharged air is being sucked back into the outdoor unit
↓
Check compressor harness and winding resistance
↓
Check IPM / inverter PCB diode path
↓
If airflow and IPM checks are normal, main PCB then compressor sequence becomes suspect
↓
Airflow / heat exchanger issue
Clean coil, clear obstruction or correct recirculation before parts replacement.
Compressor abnormal
Escalate as compressor fault after winding values are recorded.
IPM abnormal
Escalate inverter/main PCB after compressor is proven.
All checks normal
Follow manual sequence and attach readings to ticket.
Important: For overcurrent/trip, prove outdoor airflow, fan operation, heat exchanger condition, compressor windings and IPM path before PCB or compressor approval.
E:95 compressor motor control flow - Outdoor unit
Compressor motor control / rotor control error
↓
Turn unit on and confirm whether abnormal compressor noise is present
↓
Isolate supply and inspect compressor harness, terminals P400 U, P401 V, P402 W and inverter PCB solder joints
↓
Check compressor winding resistance: AOTH30KNTA approximately 1.125 Ω at 25°C; AOTH34KNTA approximately 1.120 Ω at 20°C
↓
Check IPM diode path and DC bus / inverter output
↓
If compressor winding is abnormal, escalate compressor. If winding is normal but IPM path abnormal, escalate PCB/IPM
↓
Abnormal compressor noise
Record noise and complete winding/IPM checks before compressor approval.
Harness burnt/loose/miswired
Repair or replace harness/terminal, reset and retest.
Winding abnormal
Escalate compressor after all U-V/V-W/U-W values are recorded.
IPM abnormal / windings OK
Escalate inverter/main PCB with compressor readings attached.
Important: Do not approve a compressor or PCB without recording U-V, V-W, U-W resistance, harness condition and IPM diode readings.
E:A1 discharge temperature error flow - Outdoor unit
Discharge temperature protection after compressor operation
↓
Primary check: suspect refrigerant leak / insufficient refrigerant first
↓
Check 3-way valves are fully open
↓
Check EEV operation / coil resistance, capillary tube and strainer restriction
↓
Check outdoor fan operation and heat exchanger for foreign matter, blocked fins or recirculation
↓
Check discharge thermistor value at P15 and PCB 5 V return voltage
↓
Only after refrigerant, valve, EEV, airflow and thermistor checks are proven should PCB be considered
↓
Leak / insufficient refrigerant
Repair leak, pressure test, evacuate and weigh in correct R32 charge.
3-way valve 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.
Discharge thermistor abnormal
Replace thermistor or repair harness after value is confirmed against temperature.
All checks pass
PCB becomes suspect only after refrigerant circuit evidence is complete.
Important: The main cause to prove first is refrigerant leak or insufficient refrigerant. Do not jump directly to PCB replacement.
E:A3 compressor temperature error flow - Outdoor unit
Compressor temperature protection
↓
Primary check: confirm refrigerant amount, return gas condition and whether compressor is overheating due to undercharge or restriction
↓
Check 3-way valves are fully open
↓
Check EEV operation, strainer restriction and pipe temperature split
↓
Check outdoor airflow, fan operation and coil condition
↓
Check compressor temperature thermistor at P10 and compare resistance/voltage to actual temperature
↓
If refrigerant, airflow, EEV and thermistor are proven normal, PCB/control fault becomes suspect
↓
Refrigerant issue
Repair leak or restriction, evacuate and weigh in R32 charge.
Valve/EEV issue
Correct valve or EEV/strainer issue and retest.
Airflow issue
Correct fan/coil/recirculation before parts approval.
Thermistor abnormal
Replace thermistor after measured value is confirmed against temperature.
All checks pass
PCB/control becomes suspect with full evidence.
Important: Compressor temperature faults are system-condition faults first; verify refrigerant circuit and thermistor before PCB decision.
6. Step-by-step phone support SOPs
SOP 1 - Intake and safety gate
- Confirm caller name, company, site address, indoor model/serial and outdoor model/serial.
- Confirm exact symptom: LED flash pattern, mode, when it occurs and whether repeatable.
- Confirm R32 safety controls: area ventilated, no ignition sources, suitable leak detector, qualified refrigerant handler for refrigerant circuit work.
- Confirm electrical safety: no burning smell, water ingress, damaged wiring or repeated breaker trips.
- Confirm tools: multimeter with AC/DC volts, resistance and diode test.
- If caller is not qualified or cannot safely identify terminals, stop at non-invasive checks and arrange authorised attendance.
SOP 2 - LED memory and outdoor display
- Stop operation and disconnect power.
- Reconnect power. During the 3 minute ST period, start operation and press TEST RUN on wireless remote, or press MANUAL AUTO for 10 seconds or more.
- Record indoor Operation/Timer/Economy flash pattern. Error memory display window is approximately 2 minutes 20 seconds.
- If outdoor ERROR LED blinks, press ENTER once on outdoor unit and record LED pattern.
- Erase only after recording evidence: press MANUAL AUTO during error memory display, or allow automatic erase after 2 hours normal operation without error.
SOP 3 - E:11 serial communication
- Reset power and confirm if E:11 returns.
- Check connection between indoor and outdoor: loose connector, open cable, mis-wiring, terminal 1-2-3 polarity and earth.
- Check outdoor supply: AC198-264 V at terminal L-N.
- Reverse transfer signal: outdoor terminal 1-3 should swing AC90-270 V.
- Forward transfer signal: outdoor terminal 2-3 should swing AC30-130 V.
- If reverse signal is abnormal, check outdoor fan motor first. If outdoor fan motor is abnormal, replace outdoor fan motor and main PCB. If fan motor is normal, main PCB becomes suspect.
- If forward signal is abnormal, check indoor fan motor. If indoor fan motor is abnormal, replace indoor fan motor and main PCB. If fan motor is normal, main PCB becomes suspect.
- Check external cause: grounding insulation and harmonic wave source near power cable.
SOP 4 - Indoor fan motor
- Power off. Rotate crossflow fan by hand and check for obstruction, dropped fan, bearing issue, dust build-up and casing contact.
- Check indoor fan motor connector CN5 and harness.
- CN5 reference: 1 Red Vm, 4 Black GND, 5 White Vcc, 6 Yellow Vsp, 7 Blue FG.
- Perform diode/circuit test as per component training. Do not disconnect or reconnect fan motor with power applied.
- Where fan motor is proven abnormal, replace fan motor and assess main PCB if motor has loaded/shorted the circuit.
SOP 5 - Outdoor fan motor
- Power off. Rotate outdoor propeller fan by hand and check obstruction, bearing, guard contact, weather damage and water ingress.
- Check P650 DC fan motor connector.
- P650 reference: 1 Red Vm, 4 Black GND, 5 White Vcc, 6 Yellow Vsp, 7 Brown FG.
- Power off circuit-test Vm and GND. If short-circuited below 300 kΩ, replace outdoor fan motor and main PCB.
- Power on testing if qualified and safe: confirm high voltage DC rail and 15 VDC control at PCB side.
- Do not disconnect fan motor with power applied.
SOP 6 - Main PCB / inverter PCB power tests
- Power on tests, if safe: AC supply at L-N, DC bus, fan high-voltage DC, 13 V / 15 V / 5 V control supplies where shown on board diagram.
- Power off tests: fuse continuity F100 30A, F101/F102 10A, F103 3.15A; diode bridge; IPM diode path; compressor winding resistance; fan motor circuit test.
- Check main PCB to inverter PCB harnesses P660/P662, P661/P663 and P350/P351.
- Boards may have protective coating. Ensure probe contact is made to solder joints/test points.
- Record all readings before PCB approval.
SOP 7 - IPM and diode bridge
- Power off and discharge safely before diode tests.
- Check diode bridge using diode mode, not resistance mode.
- Check IPM diode paths between P/N and U/V/W outputs.
- Check compressor winding balance before condemning IPM.
- If IPM path is abnormal and compressor winding is normal, escalate inverter/main PCB decision with readings.
SOP 8 - Thermistor testing
- Isolate power. Check connector is not loose, removed, pinched, miswired or open.
- Disconnect thermistor and measure resistance out of circuit. Compare to actual bulb temperature.
- Indoor CN1 values: pipe thermistor 0°C 176.03 kΩ, 20°C 62.91 kΩ, 30°C 39.57 kΩ; room thermistor 0°C 33.62 kΩ, 20°C 12.54 kΩ, 30°C 8.04 kΩ.
- AOTH30 outdoor values: compressor P10 0°C 168.60 kΩ, 20°C 62.55 kΩ, 30°C 40.01 kΩ; pipe mid/discharge P15 includes discharge 168.60/62.55/40.01 kΩ and pipe mid 176.03/62.91/39.57 kΩ at 0/20/30°C; outdoor P5 35.21/12.64/7.97 kΩ at 0/20/30°C; heat sink P700 15.83/5.90/3.78 kΩ at 0/20/30°C.
- AOTH34 outdoor values: compressor P10 168.60/62.55/40.01 kΩ; P15 discharge 168.60/62.55/40.01 kΩ and pipe mid 16.05/5.98/3.84 kΩ; P1 pipe out 16.05/5.98/3.84 kΩ; P5 outdoor 35.21/12.64/7.97 kΩ; P700 heat sink 15.83/5.90/3.78 kΩ at 0/20/30°C.
- With thermistor removed, check PCB thermistor supply, commonly 5 VDC on these circuits.
- Replace thermistor only when open/short/out of table. Replace PCB only when sensor and wiring are proven.
SOP 9 - EEV coil / strainer
- Check EEV connector P30 and cable for damage or loose connection.
- Power off and check EEV coil resistance. P30 reference: Red common; Blue/Orange/Yellow/White phase wires. Coil resistance is 46.0 Ω at 20°C between red and each phase.
- Power on restart and listen/feel for EEV initialisation noise.
- Check for temperature difference across strainer/capillary indicating restriction.
- If coil is normal but drive voltage is missing, PCB output becomes suspect.
SOP 10 - Compressor
- Power off. Inspect compressor harness and inverter PCB terminals P400 U, P401 V, P402 W.
- Check winding resistance U-V, V-W and U-W.
- AOTH30KNTA compressor winding reference is approximately 1.125 Ω at 25°C.
- AOTH34KNTA compressor winding reference is approximately 1.120 Ω at 20°C.
- If resistance is 0 Ω, open or materially imbalanced, escalate compressor.
- Check abnormal compressor noise only after confirming correct mode/demand and IPM readings.
SOP 11 - Pressure switch
- AOTH34KNTA includes a high pressure switch. Check connector P770 and wiring to pressure switch.
- Pressure switch characteristic: contact changes around 4.2 to 4.05 MPa and returns at 3.2 ±0.15 MPa.
- Confirm operating conditions, outdoor airflow and coil condition before replacing pressure switch.
- Record actual pressure, mode, fan operation, coil condition and pipe temperatures.
SOP 12 - Optional 2-wire remote / external communication
- Standard controller is wireless remote. Optional wired remote requires communication kit and is non-polar 2-wire type.
- For E:12, check terminal connection between optional wired remote controller and indoor unit, cable disconnection and CN13 power supply to remote controller.
- If CN13 is DC12 V, the wired remote controller is suspect. If CN13 is DC0 V, indoor main PCB is suspect after checking remote once again.
- Do not use a 3-wire Y1/Y2/Y3 test for this product family.
SOP 13 - External communication
- Use for E:18 when optional external input/output PCB is fitted.
- Check connection between main PCB and external input/output PCB for loose connector, open cable or mis-wiring.
- If connection checks do not improve symptom, replace external input/output PCB.
- If replacement does not improve symptom, indoor main PCB becomes suspect.
SOP 14 - Combination / capacity
- Use for E:22 and E:23.
- Confirm indoor/outdoor model combination matches service manual and installation manual.
- Check if applied refrigerant information and capacity match the connected outdoor unit.
- Correct model/wiring/application issue before PCB replacement.
SOP 15 - Manual auto button
- Use for E:35.
- Check whether MANUAL AUTO button is stuck or being held.
- Check indicator/display PCB and button operation.
- Replace affected button/indicator PCB or indoor main PCB only after physical button condition is confirmed.
SOP 16 - Current sensor
- Use for E:84.
- Check supply voltage, temporary power drop, grounding and connector condition.
- Inspect CT / current sensing connector and main/inverter PCB path.
- Check compressor and fan load before PCB approval.
SOP 17 - 4-way valve
- Use for E:99.
- Check 4-way valve solenoid connector and coil.
- Confirm relevant thermistors are fitted correctly and not pinched or out of holder.
- Check piping temperature change to prove valve position.
- If solenoid and thermistors are normal but valve does not change state, 4-way valve becomes suspect.
7. R32 refrigerant service notes
| Requirement | Instruction |
|---|---|
| Competency | Only competent personnel holding relevant refrigerant handling certification should work on or open the R32 refrigerant circuit. |
| Ignition risk | Check the area with a suitable flammable refrigerant leak detector before and during work. Control ignition sources and avoid confined spaces. |
| Charging | Use correct R32 charging procedure, recover/evacuate properly and weigh in the specified charge. AOTH30KNTA charge is 1,700 g; AOTH34KNTA charge is 2,300 g. |
| Refrigeration evidence | Before recommending parts on temperature/pressure faults, record valve positions, pipe temperatures, coil condition, fan operation, leak test and weighed charge evidence. |
8. Ticket evidence checklist
| Evidence required | Details to record |
|---|---|
| Model and serial | ASTH30KNTA or ASTH34KNTA indoor model/serial and matching AOTH30KNTA or AOTH34KNTA outdoor model/serial. |
| Safety and site condition | Qualified technician onsite, isolation status, R32 controls, leak detector, ignition source controls, water ingress/burning smell/short circuit risk. |
| LED / memory evidence | Operation/Timer/Economy flash counts, outdoor LED display, error memory result, whether fault occurs at power-up or during operation. |
| Electrical readings | Outdoor L-N supply, serial signal 1-3 and 2-3, fan motor Vm/GND test, 15 VDC/5 VDC/13 VDC supplies, fuse continuity, diode bridge and IPM diode readings. |
| Component readings | Indoor fan CN5 result, outdoor fan P650 result, thermistor kΩ and measured temperature, EEV P30 coil Ω, compressor U/V/W winding Ω. |
| Refrigeration evidence | Valve positions, mode, ambient, fan operation, coil condition, pressures, leak test, strainer temperature difference and weighed R32 charge. |
| Approval decision | State what has been proven before recommending indoor main PCB, outdoor main PCB, inverter PCB, fan motor, thermistor, EEV, compressor, pressure switch or 4-way valve. |