Commercial HVAC & VRF Fault Code Library
Quick-reference fault codes for field technicians working across commercial facilities, VRF systems, and older equipment. Each code points to the area where the controller detected an abnormal condition—it does not automatically identify the failed part.
Important: Code meanings can change by model, generation, controller, firmware, and region. Record the complete model number and confirm every code in the model-specific service manual before replacing parts. Disconnect and verify power before opening equipment.
Daikin VRV — Common Codes
| Code | General meaning | First field checks |
|---|---|---|
| A6-01 | Indoor fan motor locked | Wheel/blower obstruction, bearings, motor connector, motor feedback, PCB output. |
| A6-10 | Indoor fan overcurrent | Mechanical drag, incorrect motor, wiring, supply, motor and fan PCB. |
| A6-11 | Fan position detection fault | Motor feedback connector, harness continuity, motor sensor and PCB. |
| A8-01 | Power-supply voltage abnormality | Measured line/control voltage, loose terminals, transformer and board supply. |
| A9-01 | Electronic expansion valve fault | Coil connection/resistance, valve body, harness, command and PCB output. |
| A9-02 | Refrigerant-leak detection | Follow leak-detection procedure; inspect joints and verify charge by approved method. |
| C1-01 | Indoor PCB-to-fan PCB transmission fault | Connectors, harness, control voltage, board compatibility and water damage. |
| E3 | High-pressure protection | Air/water flow, dirty heat exchanger, fan/pump, closed valves, overcharge and sensor reading. |
| E4 | Low-pressure protection | Charge/leak, restrictions, EEV operation, airflow/load and pressure sensor. |
| F3 | Discharge temperature too high | Charge, restriction, superheat, sensor accuracy, compressor cooling and EEV control. |
| P1 | Power-supply phase imbalance | Phase-to-phase voltage under load, terminals, contactor and incoming supply. |
| U1 | Reverse phase, open phase, or power fault | Phase sequence, all fuses, disconnect, contactor and terminal voltage. |
| U2 | Supply-voltage abnormality | Brownout/overvoltage, phase loss, DC bus and power connections. |
| U4-01 | Indoor/outdoor transmission fault | Power to every unit, communication wiring, polarity/topology, shorts, addressing and boards. |
| UA-13 | Refrigerant type/configuration error | Model combination, field settings, replacement board data and specified refrigerant. |
Official references: Daikin VRV IV HR service manual and Daikin VRV W T-series installation manual.
LG Multi V 5 — Outdoor-Unit Codes
| Code | General meaning | First field checks |
|---|---|---|
| 421 / 422 / 423 | Low-pressure sensor fault (master / slave 1 / slave 2) | Sensor supply/signal, connector, harness, actual pressure and outdoor PCB input. |
| 431 / 432 / 433 | High-pressure sensor fault (master / slave 1 / slave 2) | Compare sensor reading to gauges, then inspect power, signal and connector. |
| 441 / 442 / 443 | Outdoor ambient-temperature sensor fault | Thermistor resistance versus temperature, connector, placement and harness. |
| 451 / 452 / 453 | Outdoor heat-exchanger pipe sensor fault | Thermistor value, pipe contact/insulation, connector and wiring. |
| 461 / 462 / 463 | Compressor suction-pipe temperature sensor fault | Sensor resistance, pipe contact, moisture/corrosion, harness and PCB input. |
| 501 / 502 / 503 | Missing power phase | All three phases at unit under load, fuses, contactor, loose/burned terminals. |
| 511 | Connected indoor-unit capacity ratio out of range | Indoor model/capacity list, addressing, commissioning data and allowed ratio. |
| 512 | Heat-recovery unit branch capacity exceeded | Branch assignment, connected indoor capacity and HR-unit design limits. |
Official reference: LG Multi V 5 Outdoor Units service manual. Three-digit suffixes identify different outdoor modules on applicable systems.
Carrier 38VMH Single-Phase VRF — Outdoor Codes
| Code | General meaning | First field checks |
|---|---|---|
| E2 | Indoor/outdoor communication fault | Unit power, communication terminals, continuity, polarity/topology and addressing. |
| E4 | T3 or T4 temperature-sensor fault | Condenser/ambient thermistor resistance, connector and harness. |
| E5 | Power-voltage protection | Supply voltage under load, connections, line disturbance and board power section. |
| E6 | DC fan fault | Fan obstruction, motor connector, feedback, DC supply and inverter board. |
| E7 | Discharge-temperature sensor fault | Thermistor resistance, attachment to discharge line, harness and PCB input. |
| E9 | EEPROM fault | Power-cycle only after recording data; verify board configuration and replacement-board setup. |
| H0 | Driver-board to main-board communication fault | Internal harness/connectors, board supply, moisture/heat damage and compatible boards. |
| L0 | Compressor module fault | Compressor winding/ground test, inverter output, DC bus, connectors and module cooling. |
| L1 | DC-bus undervoltage | Line voltage, rectifier/PFC section, capacitors, connections and load condition. |
| L2 | DC-bus overvoltage | Incoming voltage, regeneration/load change, PFC/rectifier and voltage sensing. |
| P1 | High-pressure protection | Condenser airflow, fan, coil, valves, charge and high-pressure sensing. |
| P2 | Low-pressure protection | Refrigerant loss/restriction, EEV, load/airflow and low-pressure sensing. |
| P3 | Input-current overload | Actual current, voltage, compressor mechanical/electrical condition and inverter. |
| P4 | High discharge-temperature protection | Charge, restriction, superheat, sensor accuracy and compressor cooling. |
| P5 | Condenser-temperature protection | Coil cleanliness, airflow, fan speed, recirculation, sensor and charge. |
Official reference: Carrier 38VMH single-phase VRF engineering manual. Do not apply this table to unrelated Carrier product families.
Official Lookup Sources for More Brands
- Mitsubishi Electric CITY MULTI: use the model-specific service manual and troubleshooting data at MyLinkDrive.
- Fujitsu AIRSTAGE VRF: manuals and controller/service-tool resources are available in the official VRF download center.
- Samsung DVM: use the Samsung HVAC technical-document center and the official VRF Coder utility.
- Toshiba VRF: current and legacy product service manuals are linked from the official archived-products library.
- LG: additional manuals and service software are available through LG Design and Service Tools.
- Daikin: search by exact model in the Daikin Resource Center.
Five-Step Field Workflow
- Photograph the nameplate, controller display, board LEDs, and wiring before resetting anything.
- Record the first fault in history, affected unit address, operating mode, temperatures, pressures, and recent work.
- Verify power, phase balance, fuses, grounds, connectors, and communication wiring before condemning electronics.
- Compare sensor readings to measured conditions and follow the manufacturer troubleshooting tree for the exact model.
- Correct the root cause, clear the fault, run through all operating modes, and document the final readings.
Have a code that is not listed? Email the brand, full model number, code, and a photo of the display to codes@ifixauto.com, or use the contact page. Verified submissions can be added to a future update.