Service Quick Reference – ASTH18/22/24KMTD & AOTH18/22/24KMTD (R32)

Models covered (full model numbers): ASTH18KMTD, ASTH22KMTD, ASTH24KMTD, AOTH18KMTD, AOTH22KMTD, AOTH24KMTD

Refrigerant R32 (flammable). Use appropriate R32-rated service practices and tools.

Important Always follow local regulations, WHS requirements, and the product’s rating label where applicable.

Contents

  1. Safety and compliance
  2. R32 refrigerant requirements
  3. Tools and materials (R32/R410A rated)
  4. System overview (power, control, commissioning flow)
  5. Refrigerant piping requirements
  6. Electrical requirements
  7. Outdoor unit installation
  8. Indoor unit installation
  9. Pressure test, evacuation, commissioning
  10. Additional refrigerant charging
  11. Indoor function settings
  12. Test run and handover
  13. Pump down (forced cooling operation)
  14. Error codes (indoor/outdoor/controller consolidated)
  15. How to test the various components
 

1) Safety and compliance

Risk note: This equipment uses R32 (flammable). Control ignition sources, ventilate work areas, and use approved leak detection methods and service tools.

  • Isolate electrical supply before opening covers or handling wiring. Verify isolation with an approved meter.
  • Use appropriate PPE for electrical work and refrigerant handling.
  • Do not vent refrigerant. Use proper recovery procedures and equipment.
  • Confirm correct earthing/grounding and insulation integrity before returning to service.
  • Observe manufacturer instructions for correct commissioning, and record commissioning results.
 

2) R32 refrigerant requirements

R32-specific service requirements: Use special tools designed for R32, and check for refrigerant leakage using an R32 leak detector.

  • Use R32-rated service equipment (hoses, manifold, vacuum pump, recovery unit, cylinder, leak detector).
  • Maintain ventilation; keep ignition sources away from the work area.
  • After any refrigerant work, confirm system integrity and leak-free operation before handover.
 

3) Tools and materials (R32/R410A rated)

Use equipment rated for the pressure class and approved for R32. Where local practice differs, follow local requirements.

  • R32-rated manifold gauge set with low-loss fittings
  • R32-rated vacuum pump and vacuum gauge (micron gauge recommended)
  • Nitrogen cylinder with regulator suitable for pressure testing and purge/braze practices
  • R32-rated leak detector
  • Electronic refrigerant scale (for accurate charging by mass)
  • Recovery machine and recovery cylinder (R32 compatible)
  • Approved flare tools and torque wrench (if flared connections are used)
  • Electrical test equipment: multimeter, insulation tester where permitted, clamp meter
  • General installation tools: level, mounting hardware, anchors, pipe supports, insulation, UV-rated cable ties, weatherproofing materials
 

4) System overview (power, control, commissioning flow)

How the system works (high-level):

  • Indoor and outdoor units communicate via serial/control wiring; many faults present as communication or sensor errors.
  • Outdoor unit uses inverter control; several outdoor error codes relate to inverter, IPM, PFC, current sensing, and thermistors.
  • Indoor unit uses sensors (room temperature, indoor heat exchanger, and optionally human sensor depending on model configuration) and controls the indoor fan motor and louvres.

Commissioning flow (recommended): install → verify wiring and polarity → evacuate → open service valves → run test operation → verify temperatures/pressures/current draw → check for leaks → confirm function settings → handover.

 

5) Refrigerant piping requirements

5.1 Pipe sizes (no tables)

Applies to: ASTH18KMTD, ASTH22KMTD, ASTH24KMTD, AOTH18KMTD, AOTH22KMTD, AOTH24KMTD

  • Liquid line: Ø6.35 mm
  • Gas line: Ø12.70 mm

5.2 Allowable piping length and height

  • Maximum total piping length: 30 m
  • Maximum height difference: 20 m
  • Pre-charge length: 15 m

5.3 Refrigerant information (base charge)

  • Refrigerant type: R32
  • Base charge (factory charge): 1270 g
 

6) Electrical requirements

Supply fundamentals (confirm rating label and local standards):

  • Power supply: 1Ø, 230 V, 50 Hz (nominal)
  • Acceptable voltage range used in troubleshooting checks: AC 198 V to AC 264 V measured at outdoor unit terminal L–N
  • Always verify correct earthing/grounding and secure terminations before energising.

Service diagnostic voltage checks:

  • If communication errors persist, check mains supply stability and noise sources (harmonic/noise equipment) and confirm grounding integrity.
  • Some serial signal checks reference a swinging AC value measured between specified terminals during communication diagnosis (follow the troubleshooting steps for the relevant error code).
 

7) Outdoor unit installation

  • Mount on a stable, level base with suitable anti-vibration measures as required.
  • Ensure clear airflow paths; avoid recirculation of discharge air.
  • Keep coil clean and unobstructed; blocked heat exchanger fins are a common contributor to inverter protection trips and over-current conditions.
  • Confirm service valve access and weatherproof any penetrations.
 

8) Indoor unit installation

  • Confirm correct mounting height and clearances; ensure condensate drainage is correctly graded and tested.
  • Confirm correct wiring and secure connectors (many indoor errors are connector/sensor related).
  • Verify indoor airflow is unobstructed and filters are correctly installed.
 

9) Pressure test, evacuation, commissioning

Manufacturer note (service manual): “Piping” air tightness test and vacuuming must be carried out firmly; refer to the installation manual for detailed procedures.

9.1 Pressure test (industry-standard approach)

  • Pressurise with dry nitrogen to an appropriate test pressure for the system and local standards (never use oxygen or compressed air).
  • Leak check all joints and service ports using an approved leak detection method (R32 compatible).
  • Hold pressure and confirm no drop over the required test period. Investigate and rectify any leakage.

9.2 Evacuation

  • Connect vacuum pump using short, large-diameter hoses where possible; minimise restrictions.
  • Evacuate to a confirmed deep vacuum (micron gauge recommended) and perform a standing vacuum test to verify dryness and tightness.
  • Only proceed to open service valves once evacuation integrity is confirmed.

9.3 Commissioning checks

  • Run test operation and confirm stable operation without error indication.
  • Verify indoor and outdoor fan operation, temperature change across the indoor coil, and stable compressor operation.
  • Confirm current draw is reasonable and no inverter protection events occur.
  • Final leak check after stabilisation.
 

10) Additional refrigerant charging

What the service manual provides: Base charge is 1270 g and pre-charge length is 15 m (maximum piping length 30 m).

The service manual does not state the “grams per metre” additional charge value in the extracted sections. If you require an exact additional charge rate, use the model’s installation manual/design manual charging table for the correct g/m figure.

10.1 Calculation framework (use the correct g/m from the installation manual)

Additional charge (g) = (Actual piping length (m) − 15 m) × Additional charge rate (g/m)
  • If actual piping length ≤ 15 m: additional charge is typically 0 g.
  • If actual piping length > 15 m: calculate additional charge and charge by mass using an electronic scale.
  • Always record final charge amount and piping length.
 

11) Indoor function settings

Entering function setting mode (indoor unit):

  1. While the air conditioner is stopped, press and hold the MANUAL AUTO button on the indoor unit for 10 seconds or more.
  2. Release the button when you hear the long “beep”. Function number is shown by the indicator lamps.
  3. Press the MANUAL AUTO button briefly to step through function numbers.
  4. Press and hold the MANUAL AUTO button to change the setting value for the selected function number.
  5. To finish: stop operation or allow the setting mode to time out as per unit behaviour; confirm operation afterwards.

Function settings in this section are transcribed as text (no tables) for AI readability.

11.1 Function list (text format)

  • Function 11 – Filter sign setting: Setting 0 = Standard (400 hours); Setting 1 = Long interval (1000 hours); Setting 2 = No filter sign.
  • Function 30 – Room temperature correction (cooling) – “Central”: Setting 0 = 0°C; Setting 1 = +0.5°C; Setting 2 = +1.0°C; Setting 3 = +1.5°C; Setting 4 = +2.0°C; Setting 5 = +2.5°C; Setting 6 = +3.0°C.
  • Function 31 – Room temperature correction (heating) – “Central”: Setting 0 = 0°C; Setting 1 = −0.5°C; Setting 2 = −1.0°C; Setting 3 = −1.5°C; Setting 4 = −2.0°C; Setting 5 = −2.5°C; Setting 6 = −3.0°C.
  • Function 35 – Room temperature correction (cooling) – “Rear”: Setting 0 = 0°C; Setting 1 = +0.5°C; Setting 2 = +1.0°C; Setting 3 = +1.5°C; Setting 4 = +2.0°C; Setting 5 = +2.5°C; Setting 6 = +3.0°C.
  • Function 36 – Room temperature correction (heating) – “Rear”: Setting 0 = 0°C; Setting 1 = −0.5°C; Setting 2 = −1.0°C; Setting 3 = −1.5°C; Setting 4 = −2.0°C; Setting 5 = −2.5°C; Setting 6 = −3.0°C.
  • Function 40 – Auto restart: Setting 0 = Enabled; Setting 1 = Disabled.
  • Function 42 – Indoor temperature sensor switching (depending on controller configuration): Setting 0 = Default; Setting 1 = Alternate per controller requirements.
  • Function 44 – Cable length (communication/remote considerations): Setting 0 = Standard; Setting 1 = Long (use where specified).
  • Function 46 – IR receiver / remote control enabling: Setting 0 = Enabled; Setting 1 = Disabled.
  • Function 48 – Room temperature sensor switching (as applicable): Setting 0 = Default; Setting 1 = Alternate per controller requirements.
  • Function 49 – Room temperature control switching (as applicable): Setting 0 = Default; Setting 1 = Alternate per controller requirements.
  • Function 60 – Cool air prevention: Setting 0 = Enabled; Setting 1 = Disabled.

If a setting does not appear to apply, confirm the installed controller type and the indoor unit variant.

 

12) Test run and handover

12.1 Test run – recommended checks

  • Confirm the system starts and runs without error indication.
  • Confirm indoor fan, louvre operation (where fitted), and indoor coil temperature response.
  • Confirm outdoor fan operation and stable compressor behaviour.
  • Confirm no abnormal noise or vibration.
  • Confirm correct remote controller operation and confirm any configured function settings.

12.2 Error memory (service diagnosis support)

Erasing error memory (two methods):

  • Manual erase: press the MANUAL AUTO button on the indoor unit while the “Error memory display” is shown (short beep ~3 seconds).
  • Automatic erase: after continuing normal operation with no error for 2 hours or longer after displaying the error memory (except FAN mode).

12.3 Handover checklist

  • Explain basic operation and filter cleaning.
  • Confirm no leaks and stable operation; provide commissioning results if required.
  • Confirm customer understands any special constraints for R32 systems (e.g., no unauthorised refrigerant work).
 

13) Pump down (forced cooling operation)

Forced cooling operation is used for pump down / service. Use caution: ensure the correct valves are operated in the correct order, and monitor pressures and unit behaviour throughout.

Starting forced cooling operation (outdoor unit):

  • Press the TEST RUN button on the outdoor unit PCB for 2 seconds or more to start forced cooling operation.
  • Forced cooling is also started if you press the TEST RUN button for 2 seconds or more while the compressor is operating.
  • Forced cooling operation stops when the TEST RUN button is pressed again.

Use this mode as directed in the service documentation and apply standard pump-down methodology (close liquid valve first, monitor suction, then close gas valve, stop unit as required).

 

14) Error codes (indoor/outdoor/controller consolidated)

How to read: Each line includes: Error code | Description (unit) | Indoor LEDs: Operation flashes, Timer flashes, Economy status | Wired remote controller display

All error code information is presented on one line per code for AI readability.

14.1 Consolidated error code list (no tables)

  • E:11 | Serial communication error (Serial reverse transfer error) (Outdoor unit) | Operation 1 flash, Timer 1 flash, Economy Continuous | Wired display 11
  • E:11 | Serial communication error (Serial forward transfer error) (Indoor unit) | Operation 1 flash, Timer 1 flash, Economy Continuous | Wired display 11
  • E:12 | Wired remote controller communication error (Indoor unit) | Operation 1 flash, Timer 2 flashes, Economy Continuous | Wired display 12
  • E:18 | External communication error (Indoor unit) | Operation 1 flash, Timer 8 flashes, Economy Continuous | Wired display 18
  • E:22 | Indoor unit capacity error (Indoor unit) | Operation 2 flashes, Timer 2 flashes, Economy Continuous | Wired display 22
  • E:23 | Combination error (Outdoor unit) | Operation 2 flashes, Timer 3 flashes, Economy Continuous | Wired display 23
  • E:26 | Address setting error in wired remote controller (Indoor unit) | Operation 2 flashes, Timer 6 flashes, Economy Continuous | Wired display 26
  • E:29 | Connected unit number error (Indoor unit) | Operation 2 flashes, Timer 9 flashes, Economy Continuous | Wired display 29
  • E:32 | Indoor unit main PCB error (Indoor unit) | Operation 3 flashes, Timer 2 flashes, Economy Continuous | Wired display 32
  • E:33 | Indoor unit motor electricity consumption detection error (Indoor unit) | Operation 3 flashes, Timer 3 flashes, Economy Continuous | Wired display 33
  • E:35 | MANUAL AUTO button error (Indoor unit) | Operation 3 flashes, Timer 5 flashes, Economy Continuous | Wired display 35
  • E:39 | Indoor unit power supply error for fan motor (Indoor unit) | Operation 3 flashes, Timer 9 flashes, Economy Continuous | Wired display 39
  • E:3A | Indoor unit communication circuit (wired remote controller) error | Operation 3 flashes, Timer 10 flashes, Economy Continuous | Wired display 3A
  • E:41 | Room temperature sensor error (Indoor unit) | Operation 4 flashes, Timer 1 flash, Economy Continuous | Wired display 41
  • E:42 | Indoor unit heat exchanger sensor error (Indoor unit) | Operation 4 flashes, Timer 2 flashes, Economy Continuous | Wired display 42
  • E:44 | Human sensor error | Operation 4 flashes, Timer 4 flashes, Economy Continuous | Wired display 44
  • E:51 | Indoor unit fan motor error (Indoor unit) | Operation 5 flashes, Timer 1 flash, Economy Continuous | Wired display 51
  • E:62 | Outdoor unit main PCB error (Outdoor unit) | Operation 6 flashes, Timer 2 flashes, Economy Continuous | Wired display 62
  • E:63 | Inverter error (Outdoor unit) | Operation 6 flashes, Timer 3 flashes, Economy Continuous | Wired display 63
  • E:64 | PFC circuit error (Outdoor unit) | Operation 6 flashes, Timer 4 flashes, Economy Continuous | Wired display 64
  • E:65 | IPM error (Outdoor unit) | Operation 6 flashes, Timer 5 flashes, Economy Continuous | Wired display 65
  • E:65 | Trip terminal L error (Outdoor unit) | Operation 6 flashes, Timer 5 flashes, Economy Continuous | Wired display 65
  • E:66 | PFC error (Outdoor unit) | Operation 6 flashes, Timer 6 flashes, Economy Continuous | Wired display 66
  • E:68 | IPM terminal L error (Outdoor unit) | Operation 6 flashes, Timer 8 flashes, Economy Continuous | Wired display 68
  • E:71 | Discharge thermistor error (Outdoor unit) | Operation 7 flashes, Timer 1 flash, Economy Continuous | Wired display 71
  • E:72 | Compressor thermistor error (Outdoor unit) | Operation 7 flashes, Timer 2 flashes, Economy Continuous | Wired display 72
  • E:73 | Outdoor unit heat exchanger thermistor error (Outdoor unit) | Operation 7 flashes, Timer 3 flashes, Economy Continuous | Wired display 73
  • E:74 | Outdoor temperature thermistor error (Outdoor unit) | Operation 7 flashes, Timer 4 flashes, Economy Continuous | Wired display 74
  • E:84 | Current sensor error (Outdoor unit) | Operation 8 flashes, Timer 4 flashes, Economy Continuous | Wired display 84
  • E:86 | High pressure switch error (Outdoor unit) | Operation 8 flashes, Timer 6 flashes, Economy Continuous | Wired display 86
  • E:94 | Trip detection (Outdoor unit) | Operation 9 flashes, Timer 4 flashes, Economy Continuous | Wired display 94
  • E:94 | Over current error (Outdoor unit) | Operation 9 flashes, Timer 4 flashes, Economy Continuous | Wired display 94
  • E:95 | Compressor motor control error (Outdoor unit) | Operation 9 flashes, Timer 5 flashes, Economy Continuous | Wired display 95
  • E:97 | Outdoor unit fan motor error (Outdoor unit) | Operation 9 flashes, Timer 7 flashes, Economy Continuous | Wired display 97
  • E:A1 | Discharge temperature error (Outdoor unit) | Operation 10 flashes, Timer 1 flash, Economy Continuous | Wired display A1
  • E:A3 | Compressor temperature error (Outdoor unit) | Operation 10 flashes, Timer 3 flashes, Economy Continuous | Wired display A3
 

15) How to test the various components

15.1 General service test approach

  • Confirm the reported symptom and check for stored error memory / current error indication.
  • Inspect connectors, wiring condition, and signs of heat damage or moisture ingress.
  • Validate supply voltage at the outdoor unit and confirm stable earthing/grounding.
  • Use the specific error code troubleshooting flow where applicable (check points and decision steps).

15.2 Communication and power supply checks (examples)

  • Supply voltage check for troubleshooting: confirm AC 198 V to AC 264 V at outdoor unit terminal L–N where directed by troubleshooting steps.
  • Noise/harmonics check: confirm no significant harmonic-producing equipment shares the circuit; confirm grounding insulation integrity.

15.3 High pressure switch test (for E:86)

Pressure switch characteristics (text format):

  • Contact: Short → Open at 4.2 to 4.05 MPa
  • Contact: Open → Short at 3.2 ±0.15 MPa

If the switch or wiring is open/disconnected, correct wiring/connector issues and reset power; otherwise follow the troubleshooting decision path (switch vs PCB).

15.4 Outdoor protection trips / over-current (E:94 examples)

  • Check outdoor airflow and heat exchanger condition (obstructions, clogged fins, recirculation, high ambient contribution).
  • Check outdoor fan operation and confirm correct fan performance.
  • If repeated inverter protection events persist, follow the service flow: inverter PCB → main PCB → compressor assessment as directed by troubleshooting.

15.5 Thermistor testing (general)

Method:

  1. Power off and isolate.
  2. Remove the thermistor connector from the relevant PCB.
  3. Measure resistance across the thermistor leads.
  4. Compare measured resistance to expected values at the current temperature (allow for normal tolerance and stabilise the sensor temperature).
  5. If the thermistor is open or shorted, replace it and reset power.

Thermistor resistance values: In the service manual, each thermistor has a resistance-vs-temperature reference and a PCB reference voltage (e.g., 5.0 V supply at thermistor input is referenced in troubleshooting steps). If you need the full numeric resistance list for each thermistor type in text form, add it in this section from the service manual’s “Thermistor resistance values” pages.

Note: This document is intentionally table-free. If you paste the thermistor value pages as text lines (temperature → resistance), the AI will reliably answer sensor-value questions.

Practical tip for AI-readability: When you add any numeric lists (thermistors, fan motor checks, PCB test points), format as “Item: value” lines or bullet points, not tables.

End of document.