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 appropriate PPE and has a suitable multimeter with diode test. For power-off tests, isolate supply and wait at least 5 minutes before touching electrical components. Do not instruct a customer or unqualified person to remove covers or perform electrical tests.
Document scope Error codes Quick map Flowcharts E:11 communication E:94 trip detection E:95 compressor control E:A1 discharge temp Fan motors EEV Thermistors Diode bridge IPM Ticket checklist
1. Document scope
| Area | Details |
|---|---|
| Indoor models | ARTH30KHTA, ARTH36KHTA, ARTH45KHTA, ARTH54KHTA, ARTH60KHTB |
| Outdoor models | AOTH30KCTA, AOTH36KCTA, AOTH45KCTA, AOTH54KCTA, AOTH60KCTA |
| System type | High static single phase high performance ducted R32 inverter heat pump. Power supply intake is at the outdoor unit. |
| Electrical range | System power supply 220-240 V ~ 50 Hz. Available voltage range 198-264 V. Indoor unit receives 220-240 V from the outdoor unit. |
| Core caution | Protective functions may operate when the unit is used outside the stated operating range. Always verify installation conditions before recommending parts. |
Single phase source note: This article has been rebuilt for the single phase AOTH30/36/45/54/60KCTA outdoor range. Do not use the previous three phase KRTA supply readings or single phase model-specific DC bus value bus reference on this product family.
How to use this guide on a call: Start with intake questions and safety gate, capture the exact error, then move to the relevant SOP. Each SOP gives the technical support operator a consistent script, expected readings and escalation point. Record readings and photos in the ticket before recommending parts.
2. Error code quick reference
Source: Working error code quick reference for the ARTH30-60KHT / AOTH30-60KCTA support article. Use the wired remote code first, then follow the linked SOP or flowchart. Confirm against the final single phase service manual when available.
| Code | Manual fault description | Phone support action / linked test | Wired remote display |
|---|---|---|---|
| E:11 | Serial communication error - reverse transfer error (Outdoor unit) | Run E:11 serial split | 11 |
| E:11 | Serial communication error - forward transfer error (Indoor unit) | Run E:11 serial split | 11 |
| E:12 | Wired remote controller communication error (Indoor unit) | Run wired remote controller test | 12 |
| E:15 | Automatic air flow adjustment error (Indoor unit) | Check indoor fan motor | 15 |
| E:18 | External communication error (Indoor unit) | Start with intake and wiring checks | 18 |
| E:23 | Combination error (Outdoor unit) | Start with intake and model confirmation | 23 |
| E:26 | Address setting error in wired remote controller (Indoor unit) | Check remote/controller setup | 26 |
| E:29 | Connected unit number error (Indoor unit) | Check remote/controller setup | 29 |
| E:32 | Indoor unit main PCB error (Indoor unit) | Record safety and PCB evidence | 32 |
| E:33 | Indoor unit motor electricity consumption detection error (Indoor unit) | Check indoor fan motor | 33 |
| E:39 | Indoor unit power supply error for fan motor (Indoor unit) | Check indoor fan motor | 39 |
| E:3A | Indoor unit communication circuit - wired remote controller error | Run wired remote controller test | 3A |
| E:41 | Room temperature sensor error (Indoor unit) | Run thermistor testing | 41 |
| E:42 | Indoor unit heat exchanger sensor error (Indoor unit) | Run thermistor testing | 42 |
| E:51 | Indoor unit fan motor error (Indoor unit) | Check indoor fan motor | 51 |
| E:53 | Drain pump error (Indoor unit) | Record fault and check drain pump circuit | 53 |
| E:5U | Indoor unit error (Indoor unit) | Start with intake and captured error | 5U |
| E:61.5 | Power supply detection error / phase-related display if shown (single phase outdoor) | Check single phase L-N supply, neutral, earth and voltage drop | 61 |
| E:62 | Outdoor unit main PCB error (Outdoor unit) | Record PCB evidence | 62 |
| E:62 | Outdoor Unit Model Information Error (Outdoor unit) | Confirm model / PCB information | 62 |
| E:63 | Inverter error (Outdoor unit) | Run compressor / inverter checks | 63 |
| E:64 | PFC circuit error (Outdoor unit) | Run compressor / inverter checks | 64 |
| E:65 | Trip terminal L error (Outdoor unit) | Run compressor / inverter checks | 65 |
| E:71 | Discharge thermistor error (Outdoor unit) | Run thermistor testing | 71 |
| E:72 | Compressor thermistor error (Outdoor unit) | Run thermistor testing | 72 |
| E:73 | Outdoor unit heat exchanger liquid outlet thermistor error (Outdoor unit) | Run thermistor testing | 73 |
| E:73 | Heat exchanger (Middle/Outlet) temperature thermistor error (Outdoor unit) | Run thermistor testing | 73 |
| E:74 | Outdoor temperature thermistor error (Outdoor unit) | Run thermistor testing | 74 |
| E:77 | Heat sink thermistor error (Outdoor unit) | Run thermistor testing | 77 |
| E:84 | Current sensor error (Outdoor unit) | Run supply / inverter checks | 84 |
| E:86 | High pressure switch error (Outdoor unit) | Check airflow, coil and pressure switch circuit | 86 |
| E:86 | Pressure sensor error (Outdoor unit) | Check pressure sensor circuit and readings | 86 |
| E:94 | Trip detection (Outdoor unit) | Run E:94 flow | 94 |
| E:95 | Compressor motor control error (Outdoor unit) | Run E:95 flow | 95 |
| E:97 | Outdoor unit fan motor error (Outdoor unit) | Check outdoor fan motor | 97 |
| E:99 | 4-way valve error (Outdoor unit) | Check 4-way valve / thermistors / coil | 99 |
| E:A1 | Discharge temperature error (Outdoor unit) | Run E:A1 flow | A1 |
| E:A3 | Compressor temperature error (Outdoor unit) | Check refrigerant / compressor thermistor path | A3 |
| E:A5 | Low pressure error (Outdoor unit) | Check refrigerant, EEV / strainer and pressure sensor | A5 |
| E:AC | Heat sink temperature error (Outdoor unit) | Check heat sink, airflow and thermistor | AC |
Outdoor LED table note: The service manual also includes the outdoor error code table with POWER/MODE, ERROR, PUMP DOWN, LOW NOISE and PEAK CUT lamp patterns. Use the wired remote code first where available, then use the outdoor LED table when the remote code is unavailable.
3. Quick test selection map
| Error / symptom | Use this SOP first | Follow-on checks |
|---|---|---|
| E:11 serial communication | SOP 4 - Indoor / outdoor serial signal split | If no indoor signal: check indoor fan motor(s). If no outdoor signal: disconnect outdoor fan(s), re-check signal, then check outdoor fan motor(s), EEV, thermistors, diode bridge and IPM before approving PCB. |
| E:12 or E:3A remote communication | SOP 3 - Wired remote controller signal test | Remote controller, controller cable, indoor communication path. |
| E:51 or E:97 fan motor issue | SOP 9 - DC fan motor diagnosis | Fan motor diode test, mechanical rotation, Vm to GND condition, PCB damage risk. |
| Low pressure / hunting / suspected EEV issue | SOP 8 - Outdoor EEV coil and valve operation | EEV coil resistance, seating, PCB drive, valve movement. |
| E:A1 discharge temperature error | E:A1 flow - Discharge temperature error | Main cause is normally refrigerant leak / insufficient refrigerant. Also check 3-way valve open, EEV/capillary/strainer, outdoor fan and heat exchanger, discharge thermistor and main PCB. |
| E:71-E:77 thermistor errors | SOP 6 - Thermistor testing | Thermistor supply, return voltage, k-ohm resistance and temperature comparison. |
| E:94 trip detection | E:94 flow - Trip detection outdoor unit | Check outdoor fan operation and heat exchanger first, then visually inspect compressor harness, check compressor winding resistance and check IPM. |
| E:95 compressor motor control error | E:95 flow - Compressor motor control error | Listen for abnormal compressor noise, visually inspect compressor harness, check compressor winding resistance and check IPM. |
| E:63, E:64, E:65 | SOP 10 - Compressor, IPM and bridge rectifier diagnosis | Supply, DC bus, bridge rectifier, IPM, compressor winding resistance and insulation. |
4. Clickable diagnostic flowcharts
Main triage flow
↓
↓
↓
E:11 communication split flow
↓
↓
↓
Indoor side signal check Is indoor signal present?
| Outdoor side signal check Is outdoor signal present?
|
Important split: No indoor signal leads to indoor fan motor checks. No outdoor signal leads to outdoor fan disconnection, outdoor serial re-check, and the outdoor component checks before approving the outdoor controller PCB.
E:94 trip detection flow - Outdoor unit
↓
↓
↓
↓
↓
Harness burnt or loose connection found Repair or replace affected harness or terminal connection. Do not fit PCB until connection integrity is restored. | Compressor winding value abnormal or insulation failed Escalate as compressor fault after values are recorded. | IPM diode path abnormal Escalate as IPM / back power board fault after values are recorded. |
Important: For E:94, do not jump straight to inverter PCB replacement. Check airflow and heat exchanger condition first, then prove the compressor harness connection, compressor winding resistance and IPM diode readings.
E:95 compressor motor control error flow - Outdoor unit
↓
↓
↓
↓
↓
Abnormal compressor noise present Record noise evidence and continue compressor / harness checks before recommending compressor. | Harness burnt, loose, open or mis-wired Repair/replace affected harness or terminal connection, then reset power and retest. | Compressor winding value abnormal or insulation failed Escalate as compressor fault after values are recorded. | IPM diode path abnormal Escalate as IPM / back power board fault after values are recorded. |
Important: For E:95, the compressor harness and terminals must be physically inspected because the harness can burn, overheat or lose connection. Do not move directly to inverter PCB replacement without recording harness condition, compressor winding resistance and IPM diode readings.
E:A1 discharge temperature error flow - Outdoor unit
↓
↓
↓
↓
↓
↓
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 / capillary / strainer issue Confirm coil resistance, seating, operation noise and temperature difference across restriction. | Discharge thermistor abnormal Replace thermistor / repair harness only after value is confirmed against temperature. | All checks pass but E:A1 remains Main PCB becomes suspect after refrigerant, valves, EEV, airflow and thermistor are proven. |
Important: Treat E:A1 as a refrigerant / system condition fault first. The most common cause is refrigerant leak or insufficient refrigerant. Do not recommend main PCB until the refrigerant circuit, service valves, EEV/strainer, outdoor fan/heat exchanger and discharge thermistor have been checked and recorded.
5. Step-by-step phone support SOPs
SOP 1 - Intake and safety gate
Purpose: Confirm the caller, model and risk position before giving any electrical or refrigerant testing instruction.
- Confirm caller name, company, site address, indoor model/serial and outdoor model/serial.
- Confirm exact complaint: error code, operating mode, when it occurs and whether it is repeatable.
- Confirm safety: no burning smell, water ingress, damaged wiring, repeated breaker trips or refrigerant odour.
- Confirm tools: multimeter with AC/DC volts, resistance and diode test.
- For power-off testing, instruct isolation and a minimum 5 minute wait before touching electrical components.
Decision point: If the caller is not qualified or cannot identify terminals safely, stop at non-invasive checks and arrange authorised attendance.
SOP 2 - Capture the error correctly
Purpose: Avoid unnecessary parts replacement by identifying whether the fault is an indoor, outdoor, communication or protection error.
- Ask the technician to read the wired remote controller error exactly if available.
- If using indoor LEDs, capture the operation / timer / economy flash pattern.
- If using the outdoor display, confirm the outdoor error/LED pattern after safe access.
- Ask when the error occurs: at power-up, on fan start, on compressor start, during running, or during mode change.
- Record the error code and flash pattern in the ticket before commencing tests.
SOP 3 - Wired remote controller signal test
Purpose: Split a controller communication concern between the controller, cable and indoor PCB.
- Confirm the installation uses a wired remote controller before applying Y1 / Y2 / Y3 values.
- Set meter to DC volts. With controller connected, measure Y1 to Y3. Expected value is 12 V DC, not less than 11.4 V DC.
- Isolate power before disconnecting Y2 from the rear of the controller.
- Measure between Y3 and the disconnected Y2 wire going back to the indoor unit. Expected value is a fluctuating 7-11 V DC pulse.
- Measure between Y3 and the Y2 terminal on the controller. Expected value is a fluctuating 7-11 V DC pulse.
SOP 4 - Indoor / outdoor serial communication split
Purpose: Diagnose E:11 and no communication faults by separating the indoor signal, outdoor signal, field cable and connected loads.
- Confirm correct field wiring and terminal order at both indoor and outdoor units. Look for loose terminals, open cable, mis-wiring and damaged conductors.
- Confirm supply. For the communication test reference, outdoor L-N must be within 198-264 V AC.
- Isolate power and remove the signal wire from terminal 3 at the outdoor unit. Secure the loose conductor.
- Reapply power safely. Set meter to DC volts.
- Check indoor side: black lead on neutral and red lead on the indoor signal wire. Expected indoor signal is 50-250 V DC.
- Check outdoor side: black lead on neutral and red lead on the outdoor terminal 3 signal output. Expected outdoor signal is 3-110 V DC.
- If both signals are present with the interconnect cable removed, suspect field cable, short to earth, crossed conductors or external electrical noise.
- If there is no indoor signal from the indoor side, check the indoor fan motor(s) using SOP 9A. If indoor fan motor(s) test OK and no signal remains, suspect the indoor controller PCB.
- If there is no outdoor signal from the outdoor PCB, disconnect the outdoor fan(s) and re-check the outdoor serial signal.
- If the outdoor signal returns after disconnecting the outdoor fan(s), complete outdoor fan motor diode testing using SOP 9B.
- If there is still no outdoor signal after disconnecting the outdoor fan(s), the outdoor controller PCB is likely defective. Before approval, complete and record:
| Check | Expected result / next action |
|---|---|
| Indoor signal | 50-250 V DC. If absent, check indoor fan motor(s). |
| Outdoor signal | 3-110 V DC. If absent, disconnect outdoor fan(s) and re-check signal. |
| Outdoor signal returns after fan disconnection | Outdoor fan motor is affecting the signal. Complete outdoor fan motor diode test. |
| Outdoor signal still absent after fan disconnection | Outdoor controller PCB likely defective, but only after outdoor component checks are completed and recorded. |
SOP 5 - Single phase supply and DC bus check
Purpose: Handle supply, inverter trip and no DC bus complaints on the single phase AOTH30/36/45/54/60KCTA outdoor units without applying the previous three phase KRTA values.
- Confirm this is a single phase AOTH30KCTA, AOTH36KCTA, AOTH45KCTA, AOTH54KCTA or AOTH60KCTA outdoor unit.
- Check supply at the outdoor unit L-N. Expected nominal supply is 220-240 V AC, 50 Hz.
- Confirm voltage remains within the available operating range of 198-264 V AC.
- Check active to earth and neutral to earth to identify neutral issues, poor earthing or site supply abnormalities.
- Confirm circuit protection and wiring are suitable: 25 A breaker for AOTH30/36KCTA and 32 A breaker for AOTH45/54/60KCTA, subject to local electrical rules.
- Confirm power cable is appropriately sized and that voltage drop is controlled. The design manual reference uses 4.0 mm² power cable, 1.5 mm² connection cable and a 76 m limited wiring length.
- For DC bus checks, use the single phase service data for the exact model. Do not use the previous three phase single phase model-specific DC bus value reference.
Decision point: If supply is outside 198-264 V AC, correct the site power issue before recommending PCB, inverter or compressor parts.
SOP 6 - Thermistor testing
Purpose: Validate sensor faults and protection faults before replacing PCB or refrigerant parts.
- Identify the exact sensor being tested: room, pipe, discharge, compressor, outdoor air, heat exchanger or heat sink thermistor.
- Power-on test: measure the supply from ground to one side of the thermistor. Expected supply is 5 V DC.
- Measure the return voltage from ground to the other side of the thermistor. Expected return is below 5 V DC and must align with the temperature chart.
- Power-off test: isolate power, wait 5 minutes, unplug the thermistor and measure resistance in k-ohms.
- Inspect the bulb and harness for poor seating, sweating damage, corrosion, crushed cable or short to earth.
- Compare the measured resistance to actual bulb temperature and the chart before recommending replacement.
Record: thermistor location, actual temperature, resistance, return voltage and whether there is any short to earth.
SOP 8 - Outdoor EEV coil and valve operation
Purpose: Confirm EEV electrical condition, PCB drive and mechanical operation before diagnosing refrigerant starvation or low pressure.
- Identify the EEV connector and wire colours for the model. Isolate power, wait 5 minutes and unplug the EEV coil.
- Measure from red/common to blue, orange, yellow and white.
- Expected value is 46 ohms ± 3 ohms at 20°C.
- Check each wire to earth. Expected result is open circuit.
- Where required, check for PCB drive reference of DC 12 V.
- Listen for EEV operation noise at power-up and inspect physical seating of the coil.
- For E:A1, also check for capillary tube or strainer restriction. A temperature difference across a strainer or capillary path can indicate restriction.
| Check | Expected result |
|---|---|
| Red to blue / orange / yellow / white | 46 ohms ± 3 ohms at 20°C |
| Any wire to earth | Open circuit |
SOP 9 - DC fan motor diagnosis
Purpose: Determine whether fan faults are motor, mechanical restriction or PCB supply/feedback related.
SOP 9A - Indoor fan motor check for no indoor communication signal
- Use this section when the E:11 split test shows no signal coming from the indoor side.
- Isolate power and wait at least 5 minutes before unplugging the indoor fan motor.
- Check fan wheel / blower for free rotation, obstruction, water damage or bearing failure.
- Identify 5-wire fan motor pins: red = high voltage DC/Vm, black = ground/GND, white = 15 V control/Vcc, yellow = speed command/Vsp, brown/blue = feedback/FG.
- Perform the diode tests listed in the fan motor table below.
- If the indoor fan motor fails diode/resistance checks, resolve the fan motor fault before replacing the indoor PCB.
- If indoor fan motor checks are normal and the indoor serial signal remains absent, suspect the indoor controller PCB.
SOP 9B - Outdoor fan motor check for no outdoor communication signal
- Use this section when the E:11 split test shows no signal coming from the outdoor PCB.
- Isolate power and wait at least 5 minutes before unplugging the outdoor fan motor(s).
- With outdoor fan(s) disconnected, re-check outdoor serial signal. Expected signal is 3-110 V DC.
- If the outdoor serial signal returns after fan disconnection, complete diode checks on each outdoor fan motor.
- If the outdoor serial signal does not return after fan disconnection, continue to EEV, thermistor, diode bridge and IPM checks before recommending the outdoor controller PCB.
| Fan motor check | Expected result |
|---|---|
| Mechanical rotation | Free rotation with no obstruction or bearing fault |
| Vm to GND | Not shorted below 300 k-ohms |
| Red lead to red / black lead to black | Open circuit |
| Red lead to red / black lead to white | 0.5-1.8 V |
| Red lead to black / black lead to red | 0.8-1.1 V |
| Red lead to black / black lead to white | 0.4-0.6 V |
Important: Do not disconnect fan motors while power is applied. If a fan motor has failed destructively, assess associated PCB damage risk before reconnecting or fitting a new motor.
SOP 10 - Compressor, IPM and bridge rectifier diagnosis
Purpose: Guide high-risk inverter/compressor testing after supply, wiring, fan, EEV and thermistor checks have been considered.
- Start only when the symptom supports inverter / compressor diagnosis, such as E:63, E:64, E:65, E:94 or E:95, or no outdoor serial signal remains after the outdoor fan disconnection process.
- Isolate power, wait at least 5 minutes and confirm capacitors have discharged before touching inverter components.
- Check compressor terminal wiring: R(U) red, S(V) white and C(W) black. Check compressor winding resistance between U-V, V-W and U-W. All three readings should be equal and within the model value below.
- Compressor winding resistance:
- Isolate power and disconnect the compressor harness before resistance testing.
- Measure U-V, V-W and U-W. All three readings should be equal or very close to equal.
- Use the model-specific single phase KCTA service value where available. Do not use the previous KRTA three phase table values.
- As a general inverter compressor guide only, values are normally low-ohm. Record the actual values before recommending a compressor.
- If winding resistance is 0 ohms or infinite, stop and recommend compressor replacement path subject to site confirmation.
- Insulation test windings to earth should be greater than 1 megaohm.
SOP 10A - Compressor harness and terminal visual inspection
Use this test when: E:94 or E:95 is present, compressor does not start correctly, inverter over-current is suspected, or the unit has a history of intermittent compressor trip faults.
- Isolate supply and wait at least 5 minutes before touching compressor or inverter wiring.
- Remove the compressor terminal cover and visually inspect the compressor harness cable and terminal block.
- Look for burnt insulation, heat marks, loose terminals, poor contact, arcing marks, damaged spade terminals, loose crimping, open cable or signs the harness has been hot.
- Confirm R(U), S(V) and C(W) connections are secure and correctly seated.
- If the harness or terminal connection is burnt, loose, open or mis-wired, repair/replace the affected harness or connection before condemning the compressor or PCB.
- After harness condition is confirmed, continue to compressor winding resistance and IPM diode checks.
SOP 10B - Diode bridge on back power board
Use this test when: outdoor serial signal remains absent after the outdoor fan(s) are disconnected, DC bus is abnormal, or inverter-related faults are present.
- Power-on reference: L-N should be 220-240 V AC nominal and must remain within 198-264 V AC.
- Check active to earth and neutral to earth for site supply or neutral issues.
- DC OUT + to - must be checked against the single phase KCTA service data. Do not use the previous three phase single phase model-specific DC bus value reference.
- For power-off checking, isolate supply, wait 5 minutes and use diode function to verify the bridge is not shorted and each leg conducts one way only as per training procedure.
- If AC supply is correct but DC OUT is absent or clearly abnormal, suspect the bridge rectifier or associated power board path.
SOP 10C - IPM on back power board
Use this test when: outdoor serial signal remains absent after the outdoor fan disconnection process, inverter faults are present, or the back power board is suspected.
- Identify P, N and U/V/W on the IPM test points.
- Use diode test with power isolated and capacitors discharged.
- Training reference: approximately 0.4 V through each P-U / P-V / P-W path and each U-N / V-N / W-N path.
- P to N reference is approximately 0.7-0.9 V and N to P should be open circuit.
- Any hard short, fully open abnormal path, or inconsistent leg readings should be treated as an IPM/power board fault.
Decision point: Do not recommend the outdoor controller PCB from a missing outdoor serial signal alone. Record outdoor fan motor diode readings, EEV coil resistance, thermistor values, diode bridge results and IPM results.
SOP A1 - Discharge temperature error
Purpose: Diagnose E:A1 discharge temperature protection by proving refrigerant condition, service valve position, EEV/strainer operation, outdoor airflow and the discharge thermistor before considering main PCB.
SOP A1A - Refrigerant leak / insufficient refrigerant check
- Use this as the primary diagnostic path for E:A1, as refrigerant leak or insufficient refrigerant is the main cause.
- Ask whether the system has a history of gas top-up, previous leak repair, long pipe run, recent relocation or poor performance before the fault appeared.
- Check for signs of oil staining at flare joints, service valves, indoor coil, outdoor coil, brazed joints and pipework.
- Use an appropriate leak detector and pressure test process where required by service procedure.
- If refrigerant quantity is suspect, recover and weigh charge rather than relying only on pressure readings.
- After leak repair, pressure test, evacuate correctly and weigh in the correct charge before re-testing operation.
SOP A1B - 3-way valve open check
- Check that the 3-way valve is fully open before deeper diagnosis.
- For cooling operation, check the gas side of the 3-way valve.
- For heating operation, check the liquid side of the 3-way valve.
- If the valve is closed or partially open, open fully and re-test operation.
- If the system has run with a closed or restricted valve, continue with discharge thermistor and compressor/inverter checks as required.
SOP A1C - Discharge temperature thermistor check
- Isolate power, wait at least 5 minutes, then disconnect the discharge temperature thermistor from the PCB for resistance testing.
- Measure thermistor resistance and compare it to actual sensor temperature.
- Training reference at 20°C: discharge temperature thermistor is approximately 64.50 kΩ and approximately 0.83 V DC return.
- Power-on reference: thermistor supply should be 5 V DC and return voltage should be plausible for the measured temperature.
- Inspect harness for open circuit, poor plug seating, rubbed insulation, corrosion or short to earth.
- If the thermistor reading is outside expected range for the actual temperature, replace thermistor or repair harness as applicable.
SOP A1D - Main PCB consideration
- Main PCB is a final consideration, not the first recommendation.
- Only consider main PCB after refrigerant leak/charge, 3-way valve position, EEV/capillary/strainer, outdoor fan/heat exchanger and discharge thermistor have been checked.
- Record all measured values and observations before approving PCB replacement.
Linked tests:
6. Ticket checklist before recommending parts
Record the following in the ticket:
- Exact indoor and outdoor model numbers and serial numbers.
- Exact error code and when it occurs.
- Supply readings taken.
- Whether outdoor terminal 3 was removed for the communication split test.
- Indoor serial signal reading. If absent, record indoor fan motor test results.
- Outdoor serial signal reading. If absent, record whether outdoor fan(s) were disconnected and whether the signal returned.
- Outdoor fan motor diode readings if outdoor no-signal path was used.
- Outdoor EEV coil resistance results.
- Outdoor thermistor identity, temperature, resistance and return voltage.
- Diode bridge results on the back power board.
- IPM results on the back power board.
- Photos of wiring, PCB area and meter readings where practical.
- E:94 trip detection checks: outdoor fan / heat exchanger condition, compressor harness visual inspection, compressor winding resistance and IPM diode results.
- E:95 compressor motor control checks: abnormal compressor noise, compressor harness visual inspection, connector condition, compressor winding resistance and IPM diode results.
- E:A1 discharge temperature checks: refrigerant leak / charge condition, 3-way valve position, EEV/capillary/strainer checks, outdoor fan and heat exchanger condition, discharge thermistor value and main PCB consideration.
Recommended wording for E:A1 cases: “E:A1 discharge temperature error checked. Refrigerant leak / insufficient refrigerant considered as primary cause. 3-way valve position confirmed. EEV/capillary/strainer checked. Outdoor fan operation and heat exchanger condition checked. Discharge thermistor resistance and DC return checked against actual temperature. Main PCB only considered after the above checks were recorded.”
Recommended wording for E:95 cases: “E:95 compressor motor control error checked. Compressor operation noise reviewed. Compressor harness and terminals visually inspected for burning, loose connection, open cable or mis-wiring. Compressor winding resistance checked across U-V, V-W and U-W. IPM diode test completed and recorded. Recommendation based on recorded values.”
Recommended wording for E:94 cases: “E:94 trip detection checked. Outdoor fan operation, air passage, heat exchanger and ambient/recirculation conditions reviewed. Compressor harness visually inspected for burning, loose terminals and poor connection. Compressor winding resistance checked across U-V, V-W and U-W. IPM diode test completed and recorded. Recommendation based on recorded values.”
Recommended wording for E:11 outdoor no-signal cases: “E:11 serial communication split test completed. Outdoor terminal 3 isolated. Outdoor serial signal absent. Outdoor fan(s) disconnected and signal re-tested. Follow-on checks completed on outdoor fan motor diode readings, EEV coil resistance, outdoor thermistor values, diode bridge and IPM. Based on recorded results, outdoor controller PCB recommendation supported.”
Recommended wording for E:11 indoor no-signal cases: “E:11 serial communication split test completed. Indoor serial signal absent. Indoor fan motor(s) checked for mechanical condition and diode readings. Based on recorded results, indoor controller PCB / indoor fan motor recommendation supported.”