GENERAL AIRSTAGE Technical Reference
ASTG09KMCB / ASTG12KMCB Service Reference
Specifications, controls, test operation, error codes, diagnostics and key service parts
Indoor units ASTG09KMCB / ASTG12KMCB with outdoor units AOTG09KMCB / AOTG12KMCB
This article consolidates the key information from the service instruction and service manual for the KMCB wall-mounted R32 split systems. It is intended as a field-service reference; use the full service documentation where detailed disassembly, PCB circuit or component-level procedures are required.
Qualified personnel only: Electrical and refrigerant-system testing must be carried out by appropriately qualified personnel. Isolate power before accessing electrical components and follow applicable electrical, refrigerant and safety requirements.
1. Applicable models and specifications
| Indoor unit | Outdoor unit | Cooling capacity | Heating capacity |
|---|---|---|---|
| ASTG09KMCB | AOTG09KMCB | 2.50 kW | 3.20 kW |
| ASTG12KMCB | AOTG12KMCB | 3.50 kW | 3.70 kW |
| Item | Specification |
|---|---|
| Power supply | Single phase 240 V, 50 Hz |
| Refrigerant | R32 |
| Factory refrigerant charge | 850 g |
| Liquid pipe | 1/4 in (6.35 mm) |
| Gas pipe | 3/8 in (9.52 mm) |
| Maximum piping length | 20 m |
| Maximum piping height | 15 m |
| Indoor dimensions (H x W x D) | 268 x 840 x 203 mm |
| Outdoor dimensions (H x W x D) | 540 x 790 x 290 mm |
Compressor operating frequency range
| Model | Cooling | Heating | Dry |
|---|---|---|---|
| AOTG09KMCB | 20-74 rps | 20-100 rps | 25-35 rps |
| AOTG12KMCB | 20-88 rps | 20-105 rps | 27-35 rps |
2. Key control operation
- Cooling: compressor frequency is modulated from the difference between room temperature and set temperature. Maximum frequency is also limited by fan setting and outdoor temperature.
- Heating: compressor frequency increases as room temperature falls below setpoint and is reduced or stopped as the room rises above setpoint.
- Dry: compressor frequency is controlled in fixed zones based on the indoor room-temperature sensor.
- Auto changeover: the system selects heating, cooling/dry or monitoring based on room temperature, setpoint and outdoor temperature.
- Indoor fan: Auto, Quiet, Low, Medium and High are available. Heating includes cool-air-prevention control based on indoor heat-exchanger temperature.
- Electronic expansion valve: opening is calculated from compressor frequency and temperature-sensor inputs. After the compressor stops, the valve is driven to 480 pulses after 110 seconds. On power-up it is initialised with 528 closing-direction pulses.
- Compressor restart protection: restart is inhibited for approximately 3 minutes after stopping.
- Compressor preheating: when the outdoor heat exchanger is below 5°C and the system has been stopped for 30 minutes, the compressor is energised for preheating. Preheating ends when operation starts or outdoor heat-exchanger temperature reaches 7°C or above.
Defrost: during heating, defrost is initiated according to compressor accumulated run time, outdoor temperature and outdoor heat-exchanger temperature. Defrost ends when the outdoor heat-exchanger sensor rises above approximately 16°C or the compressor has operated in defrost for 15 minutes.
3. Test operation / forced cooling
- If normal operation is prevented by room temperature, press and hold the MANUAL AUTO button on the indoor unit for more than 10 seconds.
- During cooling test operation, the OPERATION and TIMER indicators flash simultaneously.
- If HEAT is selected from the remote controller, heating test operation begins after approximately 3 minutes.
- To finish test operation, press the remote controller START/STOP button.
Forced cooling: holding MANUAL AUTO for 10 seconds or more also initiates forced cooling. Forced cooling operates regardless of room-temperature demand and is automatically released after 60 minutes. The OPERATION and TIMER LEDs flash 1 second ON / 1 second OFF during this operation.
4. Error code quick reference
The indoor unit uses the OPERATION, TIMER and ECONOMY lamps as a flashing error display. With a compatible wired remote controller, the corresponding error code is displayed directly.
| Code | Error description | Primary area to check |
|---|---|---|
| 11 | Serial communication error | Indoor/outdoor interconnect, supply, serial signal, PCB/fan-motor influence |
| 12 | Wired remote controller communication error | Remote cable/terminal, communication kit, controller PCB, remote controller |
| 23 | Combination error | Indoor/outdoor model combination |
| 32 | Indoor unit PCB model information error | Indoor controller PCB, connectors, EEPROM/model information |
| 35 | Manual auto switch error | Manual AUTO switch, indicator PCB, controller PCB |
| 41 | Room temperature sensor error | Room thermistor, CN4 wiring, 5 V sensor supply |
| 42 | Indoor heat-exchanger middle temperature sensor error | Pipe thermistor, CN4 wiring, 5 V sensor supply |
| 51 | Indoor fan motor error | Fan rotation, fan motor, ambient temperature, controller PCB |
| 62 | Outdoor main PCB model information error | Outdoor main PCB, power quality/noise, EEPROM/model information |
| 63 | Inverter error | Outdoor main PCB, wiring, supply/noise |
| 64 | PFC circuit error | Supply voltage, power-quality/noise, connectors, outdoor main PCB |
| 65 | Trip terminal L error | Outdoor main PCB / IPM trip signal |
| 71 | Discharge temperature sensor error | Discharge thermistor, CN70, outdoor main PCB |
| 73 | Outdoor heat-exchanger liquid temperature sensor error | Outdoor pipe thermistor, CN71, outdoor main PCB |
| 74 | Outdoor temperature sensor error | Outdoor thermistor, CN70, outdoor main PCB |
| 84 | Current sensor error | Outdoor current sensing / main PCB |
| 94 | Trip detection | Compressor/inverter current and outdoor PCB |
| 95 | Compressor rotor position detection error | Compressor, compressor wiring, inverter/main PCB |
| 97 | Outdoor unit fan motor error | Outdoor fan motor, CN800, outdoor main PCB |
| 99 | 4-way valve error | 4-way valve coil, refrigerant cycle, outdoor PCB output |
| A1 | Discharge temperature error | Refrigerant condition, discharge temperature, airflow, EEV, compressor |
5. Common diagnostic checks
E:11 - Serial communication
- Reset power and confirm whether the fault returns.
- Check the indoor-to-outdoor interconnecting cable for loose, removed or incorrect connections.
- Check outdoor supply at terminals L-N. The service instruction specifies approximately AC198-264 V.
- For reverse serial transfer, the service instruction specifies a varying measurement of approximately AC90-270 V at outdoor terminals L-3.
- For forward serial transfer, the service instruction specifies approximately AC30-130 V at outdoor terminals N-3.
- If communication remains abnormal, follow the service-instruction flow chart before replacing a PCB.
E:41 / E:42 - Indoor thermistors
| Sensor | 0°C | 20°C | 30°C |
|---|---|---|---|
| Room thermistor | 33.6 kΩ | 12.5 kΩ | 8.0 kΩ |
| Indoor pipe thermistor | 176.0 kΩ | 62.9 kΩ | 39.6 kΩ |
For E:41/E:42, inspect connector condition, wiring and thermistor resistance first. The service instruction also specifies checking for a DC5 V sensor supply at the indoor controller PCB.
Outdoor thermistor reference
| Sensor | 0°C | 20°C | 30°C |
|---|---|---|---|
| Discharge thermistor | 168.6 kΩ | 62.6 kΩ | 40.0 kΩ |
| Outdoor temperature thermistor | 35.2 kΩ | 12.6 kΩ | 8.0 kΩ |
| Outdoor pipe thermistor | 16.1 kΩ | 6.0 kΩ | 3.8 kΩ |
Protection reference: the service instruction shows discharge-temperature frequency reduction beginning at approximately 104°C, release at approximately 101°C, and compressor stop at approximately 110°C. Cooling pressure protection stops the compressor and outdoor fan if the outdoor heat-exchanger sensor reaches 65°C or higher.
6. Key service parts
Indoor unit
| Part | Part number | Notes |
|---|---|---|
| Main PCB | 9710608018 | ASTG09KMCB |
| Main PCB | 9710608025 | ASTG12KMCB |
| Display Assy | 9709642016 | Both models |
| Thermistor Assy | 9900627034 | Indoor thermistor assembly |
| Wireless LAN Adapter | 9382167042 | Factory service listing |
| Fan Motor | 9603318017 | Both models |
| Crossflow Fan Assy | 9316830004 | Both models |
| Evaporator Total Assy | 9332989120 | Both models |
Outdoor unit
| Part | Part number | Notes |
|---|---|---|
| Main PCB with grease | 9709681800 | AOTG09KMCB |
| Main PCB with grease | 9709681817 | AOTG12KMCB |
| Fan Motor | 9602864010 | Both models |
| Outdoor Thermistor | 9900565008 | Outdoor ambient sensor |
| Thermistor Assy | 9900628000 | Outdoor thermistor assembly |
| Compressor Assy | 9320416003 | Both models |
| Expansion Valve Coil | 9970095030 | Both models |
| 4-way Valve Assy | 9320412005 | Both models |
Parts ordering: Always verify the current part number against the latest GENERAL AIRSTAGE parts system before ordering. Service-manual part numbers can be superseded.
7. Service notes
- The outdoor unit uses a DC inverter rotary compressor and R32 refrigerant.
- The outdoor expansion valve coil is connected at CN40; the service manual specifies approximately 46 Ω coil resistance at 20°C.
- The outdoor fan motor connection is CN800.
- Outdoor thermistor connections are shown at CN70/CN71 in the service manual.
- Demand Response modes are supported. DR1 switches the compressor off; DR2 and DR3 limit energy consumption to 50% and 75% respectively of the rated half-hour energy reference described in the service manual.
- For component-level PCB diagnosis, refrigerant-cycle diagnosis, disassembly and no-error troubleshooting, refer to the full service instruction.
Technical information: Values in this article are taken from the ASTG09KMCB / ASTG12KMCB service instruction and service manual. Confirm model, serial number and current service documentation before replacing components or making refrigerant-system changes.