Blue Star AC error codes – VRF V Plus
64 codes from the Blue Star service manual, with what each one means and the usual causes. Codes are from the user manual table; checks are standard VRF practice - confirm with the Blue Star service manual. "MANUAL reset" codes need a power reset after fixing.
You can safely switch the unit off at the switch, wait 5 minutes and switch on again. Don't open the unit, touch wiring or handle gas: these checks need a trained technician.
A0
AC over voltage (auto reset)
What our technician checks
- Measure supply at ODU terminal block, all three phases, under load.
A1
AC under voltage (auto reset)
What our technician checks
- Measure supply at ODU terminal block, all three phases, under load.
A2
Single phasing (auto reset)
What our technician checks
- Measure R-Y, Y-B, B-R voltages and check phase sequence and loose lugs at MCB/SFU.
A7
Phase imbalance (auto reset)
What our technician checks
- Measure R-Y, Y-B, B-R voltages and check phase sequence and loose lugs at MCB/SFU.
b0
Inverter compressor 1 overload (auto reset)
What our technician checks
- Check compressor winding resistance (U-V, V-W, W-U balanced), insulation to earth, refrigerant charge and blocked condenser.
b1
Inverter compressor 2 overload (auto reset)
What our technician checks
- Check compressor winding resistance (U-V, V-W, W-U balanced), insulation to earth, refrigerant charge and blocked condenser.
b6
Inverter compressor 1 over-current (auto reset)
What our technician checks
- Check compressor winding resistance (U-V, V-W, W-U balanced), insulation to earth, refrigerant charge and blocked condenser.
b7
Inverter compressor 2 over-current (auto reset)
What our technician checks
- Check compressor winding resistance (U-V, V-W, W-U balanced), insulation to earth, refrigerant charge and blocked condenser.
b8
Inverter drive 1 overheat (auto reset)
What our technician checks
- Check drive heat-sink fan/airflow, heat-sink paste and mounting screws, condenser cleanliness, ambient temperature.
b9
Inverter drive 2 overheat (auto reset)
What our technician checks
- Check drive heat-sink fan/airflow, heat-sink paste and mounting screws, condenser cleanliness, ambient temperature.
bA
Inverter drive 1 start error (auto reset)
What our technician checks
- Check the U/V/W compressor leads from drive, winding resistance, and pressure equalisation before start.
bb
Inverter drive 2 start error (auto reset)
What our technician checks
- Check the U/V/W compressor leads from drive, winding resistance, and pressure equalisation before start.
bC
ODU fan motor 1 feedback error (auto reset)
What our technician checks
- Spin the ODU fan by hand (bearing), check fan motor connector and feedback wire, fan board supply.
bd
ODU fan motor 2 feedback error (auto reset)
What our technician checks
- Spin the ODU fan by hand (bearing), check fan motor connector and feedback wire, fan board supply.
d0
Inverter drive 1 DC over-voltage (auto reset)
What our technician checks
- Measure incoming AC and the DC-link on the drive
- check for supply spikes or sags.
d1
Inverter drive 2 DC over-voltage (auto reset)
What our technician checks
- Measure incoming AC and the DC-link on the drive
- check for supply spikes or sags.
d2
Inverter drive 1 DC under-voltage (auto reset)
What our technician checks
- Measure incoming AC and the DC-link on the drive
- check for supply spikes or sags.
d3
Inverter drive 2 DC under-voltage (auto reset)
What our technician checks
- Measure incoming AC and the DC-link on the drive
- check for supply spikes or sags.
d8
Inverter drive 1 overheat (MANUAL reset)
What our technician checks
- Check drive heat-sink fan/airflow, heat-sink paste and mounting screws, condenser cleanliness, ambient temperature.
d9
Inverter drive 2 overheat (MANUAL reset)
What our technician checks
- Check drive heat-sink fan/airflow, heat-sink paste and mounting screws, condenser cleanliness, ambient temperature.
dA
Inverter drive 1 start error (MANUAL reset)
What our technician checks
- Check the U/V/W compressor leads from drive, winding resistance, and pressure equalisation before start.
db
Inverter drive 2 start error (MANUAL reset)
What our technician checks
- Check the U/V/W compressor leads from drive, winding resistance, and pressure equalisation before start.
dC
Inverter compressor 1 over-current (MANUAL reset)
What our technician checks
- Check compressor winding resistance (U-V, V-W, W-U balanced), insulation to earth, refrigerant charge and blocked condenser.
dd
Inverter compressor 2 over-current (MANUAL reset)
What our technician checks
- Check compressor winding resistance (U-V, V-W, W-U balanced), insulation to earth, refrigerant charge and blocked condenser.
dE
Inverter drive mismatch
What our technician checks
- Confirm drive part number / capacity setting matches the ODU model.
E1
HP switch trip (auto reset)
What our technician checks
- Check condenser fan running and coil clean, service valves fully open, overcharge, non-condensables, HP switch continuity.
E2
HP switch trip 3rd time in one hour (MANUAL reset)
What our technician checks
- Check condenser fan running and coil clean, service valves fully open, overcharge, non-condensables, HP switch continuity.
E3
Low pressure error (auto reset)
What our technician checks
- Check for refrigerant leak / low charge, closed service valves, blocked strainer or EEV, IDU filters/coil.
E4
Low pressure error 3rd time (MANUAL reset)
What our technician checks
- Check for refrigerant leak / low charge, closed service valves, blocked strainer or EEV, IDU filters/coil.
E5
Inverter compressor 1 high discharge line temp (auto reset)
What our technician checks
- Check refrigerant charge (low charge = high discharge temp), EEV operation, DLT sensor value and fixing on pipe.
E6
Inverter compressor 2 high discharge line temp (auto reset)
What our technician checks
- Check refrigerant charge (low charge = high discharge temp), EEV operation, DLT sensor value and fixing on pipe.
E8
Inverter compressor 1 high DLT 4th time (MANUAL reset)
What our technician checks
- Check refrigerant charge (low charge = high discharge temp), EEV operation, DLT sensor value and fixing on pipe.
E9
Inverter compressor 2 high DLT 4th time (MANUAL reset)
What our technician checks
- Check refrigerant charge (low charge = high discharge temp), EEV operation, DLT sensor value and fixing on pipe.
Eb
ODU fan motor 1 feedback error (MANUAL reset)
What our technician checks
- Spin the ODU fan by hand (bearing), check fan motor connector and feedback wire, fan board supply.
EE
ODU fan motor 2 feedback error (MANUAL reset)
What our technician checks
- Spin the ODU fan by hand (bearing), check fan motor connector and feedback wire, fan board supply.
EC
Inverter compressor 1 overheat (MANUAL reset)
What our technician checks
- Check refrigerant charge (low charge = high discharge temp), EEV operation, DLT sensor value and fixing on pipe.
Ed
Inverter compressor 2 overheat (MANUAL reset)
What our technician checks
- Check refrigerant charge (low charge = high discharge temp), EEV operation, DLT sensor value and fixing on pipe.
F1
Ambient temperature sensor failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
F2
DLT sensor (inverter compressor 1) failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
F3
DLT sensor (inverter compressor 2) failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
F5
ODU liquid temp sensor (HEX1) failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
F6
ODU gas temp sensor (HEX1) failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
F7
ODU liquid temp sensor (HEX2) failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
F8
ODU gas temp sensor (HEX2) failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
F9
High-pressure sensor failure
What our technician checks
- Check sensor connector and 5 V supply
- compare reading with gauge pressure.
FA
Low-pressure sensor failure
What our technician checks
- Check sensor connector and 5 V supply
- compare reading with gauge pressure.
Fb
Fire alarm input from ODU
What our technician checks
- Check fire-alarm input terminals and the building fire panel signal.
Fc
Fire alarm input from IDU
What our technician checks
- Check fire-alarm input terminals and the building fire panel signal.
C1
Communication error: ODU control board ↔ ODU power board
What our technician checks
- Check the internal ribbon/communication cables and connectors between the named boards inside the ODU.
C2
Communication error: ODU control board ↔ ODU fan board
What our technician checks
- Check the internal ribbon/communication cables and connectors between the named boards inside the ODU.
C3
Communication error: master ↔ slave ODU
What our technician checks
- Check communication cable polarity, shielding, continuity and spacing from power cables (min 600 mm)
- confirm all units powered.
C4
Communication error: master ODU ↔ IDUs
What our technician checks
- Check communication cable polarity, shielding, continuity and spacing from power cables (min 600 mm)
- confirm all units powered.
C5
Communication error: IDU ↔ wired handset
What our technician checks
- Check wired handset cable and connector at IDU PCB.
C6
Auto-addressing error
What our technician checks
- Check number of IDUs vs setting, duplicate addresses and communication wiring.
C7
Communication error: inverter drive 1
What our technician checks
- Check the internal ribbon/communication cables and connectors between the named boards inside the ODU.
C8
Communication error: inverter drive 2
What our technician checks
- Check the internal ribbon/communication cables and connectors between the named boards inside the ODU.
C9
Communication error on another IDU (shown on the IDUs that are fine)
What our technician checks
- Check communication cable polarity, shielding, continuity and spacing from power cables (min 600 mm)
- confirm all units powered.
U3
IDU room temp sensor failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
U4
IDU liquid temp sensor failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
U5
IDU gas temp sensor failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
U6
IDU supply-air temp sensor failure
What our technician checks
- Unplug sensor and measure resistance against the temperature table
- check for open/short and crushed wiring.
U7
IDU float switch error (drain)
What our technician checks
- Check drain pump runs, float switch moves freely, drain pipe slope and blockage.
U8
IDU fan motor error
What our technician checks
- Check IDU fan motor connector, blower free rotation and motor supply from PCB.
U9
Mode conflict (IDU mode differs from ODU mode)
What our technician checks
- Compare IDU selected mode with the mode the ODU is running.
Code not here, or still showing?
Send a photo of the display and the model sticker on WhatsApp. We'll tell you what it means and whether it needs a visit.
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