AC Fault Codes
Diagnostic guides for major HVAC brands.
Maintenance Log: Precision Gas Charging & Power Jet AC Service on OP Road, Vadodara
Maintenance Log: Precision Gas Charging & Power Jet AC Service on OP Road, Vadodara — root causes, multimeter test values (Post-service grill supply...
Industrial Panel AC Error Code Dictionary: Rittal, Advance Cooling & CNC Cabinet Coolers
Industrial Panel AC Error Code Dictionary: Rittal, Advance Cooling & CNC Cabinet Coolers — root causes, multimeter test values (Cabinet setpoint...
Voltas Split AC Error Code E6: Indoor-Outdoor Communication Fault
Voltas Split AC Error Code E6: Indoor-Outdoor Communication Fault — root causes, multimeter test values (Fluctuating 10V–28V DC pulse between N and S...
Voltas AC Error Code H6: Indoor Blower Motor No Feedback
Voltas AC Error Code H6: Indoor Blower Motor No Feedback — root causes, multimeter test values (1.5 µF – 2.0 µF indoor PCB fan capacitor), step-by-step...
Voltas AC Error Code E5: Low Voltage & Outdoor Overcurrent Protection
Voltas AC Error Code E5: Low Voltage & Outdoor Overcurrent Protection — root causes, multimeter test values (215V–240V AC under load), step-by-step fix,...
Voltas AC Error Code E2: Indoor Evaporator Coil Sensor Fault
Voltas AC Error Code E2: Indoor Evaporator Coil Sensor Fault — root causes, multimeter test values (10 kΩ / 15 kΩ at 25°C seated tightly inside copper...
Voltas AC Error Code E1: Room Temperature Thermistor Fault
Voltas AC Error Code E1: Room Temperature Thermistor Fault — root causes, multimeter test values (10 kΩ or 15 kΩ at 25°C (model dependent) with smooth...
Voltas AC Error Code F0: Refrigerant Shortage / Metering Blockage
Voltas AC Error Code F0: Refrigerant Shortage / Metering Blockage — root causes, multimeter test values (Frost-free liquid service valve), step-by-step...
Voltas AC Error Code EC: Refrigerant Leakage / Cooling Failure
Voltas AC Error Code EC: Refrigerant Leakage / Cooling Failure — root causes, multimeter test values (R32 running pressure 120–135 PSI), step-by-step fix,...
Samsung AC Error Code E464: Outdoor IPM DC Peak Overcurrent
Samsung AC Error Code E464: Outdoor IPM DC Peak Overcurrent — root causes, multimeter test values (Balanced 0.9 Ω – 2.1 Ω across U-V-W), step-by-step fix,...
Samsung AC Error Code E203: Main MCU to Inverter Micom Timeout
Samsung AC Error Code E203: Main MCU to Inverter Micom Timeout — root causes, multimeter test values (Stable 15V, 5V, and 3.3V DC isolated power rails...
Samsung AC Error Code E201: Unit Count & Communication Interruption
Samsung AC Error Code E201: Unit Count & Communication Interruption — root causes, multimeter test values (0.7V–3.5V differential RS485 signal on F1-F2...
Samsung AC Error Code E101: 1-Minute Communication Timeout
Samsung AC Error Code E101: 1-Minute Communication Timeout — root causes, multimeter test values (Oscillating DC communication voltage on F1/F2 or N/1...
Samsung AC Error Code C154: Indoor Fan Motor Feedback Error
Samsung AC Error Code C154: Indoor Fan Motor Feedback Error — root causes, multimeter test values (5V DC Hall supply and 2.5V square-wave FG feedback...
Panasonic AC Error Code H99: Indoor Heat Exchanger Freeze Prevention
Panasonic AC Error Code H99: Indoor Heat Exchanger Freeze Prevention — root causes, multimeter test values (Clean return filters & evaporator fins),...
Panasonic AC Error Code H19: Indoor Fan Motor Mechanism Lock
Panasonic AC Error Code H19: Indoor Fan Motor Mechanism Lock — root causes, multimeter test values (Smooth free-spin of cross-flow fan), step-by-step fix,...
Panasonic AC Error Code H11: Indoor-Outdoor Communication Failure
Panasonic AC Error Code H11: Indoor-Outdoor Communication Failure — root causes, multimeter test values (25V–45V DC fluctuating pulse between Terminal 2...
Panasonic AC Error Code F97: Compressor Overheat Protection
Panasonic AC Error Code F97: Compressor Overheat Protection — root causes, multimeter test values (Discharge thermistor ~50 kΩ at 25°C), step-by-step fix,...
Panasonic AC Error Code F93: Compressor Revolution & Drive Fault
Panasonic AC Error Code F93: Compressor Revolution & Drive Fault — root causes, multimeter test values (Equal winding resistance across U-V-W),...
Mitsubishi AC Error Code U0: Refrigerant Undercharge Protection
Mitsubishi AC Error Code U0: Refrigerant Undercharge Protection — root causes, multimeter test values (Discharge superheat <35°C), step-by-step fix, and...
Mitsubishi AC Error Code P9: Condenser / Dual-Pipe Thermistor Fault
Mitsubishi AC Error Code P9: Condenser / Dual-Pipe Thermistor Fault — root causes, multimeter test values (10 kΩ at 25°C smooth negative temperature...
Mitsubishi AC Error Code P8: Pipe Temperature Abnormal in Cooling
Mitsubishi AC Error Code P8: Pipe Temperature Abnormal in Cooling — root causes, multimeter test values (Suction service valve open), step-by-step fix,...
Mitsubishi AC Error Code E7: Serial Transmission Circuit Fault
Mitsubishi AC Error Code E7: Serial Transmission Circuit Fault — root causes, multimeter test values (Clean switching waveform across indoor transmission...
Mitsubishi AC Error Code E6: Indoor/Outdoor Serial Reception Error
Mitsubishi AC Error Code E6: Indoor/Outdoor Serial Reception Error — root causes, multimeter test values (12V–24V DC intermittent pulse across S2 and S3...
MarQ AC Error Codes & Solutions: Complete Inverter & Split Guide
MarQ AC Error Codes & Solutions: Complete Inverter & Split Guide — root causes, multimeter test values (10 kΩ thermistors at 25°C), step-by-step fix, and...
Lloyd AC Error Code EC: Refrigerant Leak & Zero Cooling Alarm
Lloyd AC Error Code EC: Refrigerant Leak & Zero Cooling Alarm — root causes, multimeter test values (Suction line sweat temperature 7°C–11°C),...
Lloyd AC Error Code E5: Outdoor Sensor / Communication Protection
Lloyd AC Error Code E5: Outdoor Sensor / Communication Protection — root causes, multimeter test values (210V–245V AC input under load), step-by-step fix,...
Lloyd AC Error Code E3: Indoor Fan Speed Out of Control
Lloyd AC Error Code E3: Indoor Fan Speed Out of Control — root causes, multimeter test values (1.5 µF – 2.5 µF indoor fan capacitor within ±5% tolerance),...
Lloyd AC Error Code E2: Zero-Crossing Signal Detection Fault
Lloyd AC Error Code E2: Zero-Crossing Signal Detection Fault — root causes, multimeter test values (100Hz pulse train at MCU zero-cross pin), step-by-step...
LG AC Error Code CH 38: Refrigerant Gas Shortage Detection
LG AC Error Code CH 38: Refrigerant Gas Shortage Detection — root causes, multimeter test values (R32 standing pressure ~230–250 PSI), step-by-step fix,...
LG AC Error Code CH 21: Inverter IPM DC Peak Overcurrent
LG AC Error Code CH 21: Inverter IPM DC Peak Overcurrent — root causes, multimeter test values (Balanced 1.1 Ω – 2.4 Ω across U/V/W compressor terminals),...
LG AC Error Code CH 10: Indoor BLDC Fan Motor Lock / Feedback Error
LG AC Error Code CH 10: Indoor BLDC Fan Motor Lock / Feedback Error — root causes, multimeter test values (310V DC supply (Pin 1), 15V DC drive (Pin 4),...
LG AC Error Code CH 06: Indoor Outlet Pipe Sensor Error
LG AC Error Code CH 06: Indoor Outlet Pipe Sensor Error — root causes, multimeter test values (5 kΩ at 25°C (LG pipe sensor standard) on CN-TH2...
LG AC Error Code CH 05: Indoor-Outdoor Communication Fault
LG AC Error Code CH 05: Indoor-Outdoor Communication Fault — root causes, multimeter test values (DC voltage oscillating 5V–35V between terminal 2(N) and...
LG AC Error Code CH 01: Indoor Air Sensor Open or Short
LG AC Error Code CH 01: Indoor Air Sensor Open or Short — root causes, multimeter test values (10 kΩ at 25°C on CN-TH1 indoor PCB connector), step-by-step...
Hitachi AC Error Codes: Complete Timer LED Blink Diagnostic Guide
Hitachi AC Error Codes: Complete Timer LED Blink Diagnostic Guide — root causes, multimeter test values (4 blinks = Zero-cross/IPM), step-by-step fix, and...
Godrej AC Error Code E6: Indoor-Outdoor Communication Error
Godrej AC Error Code E6: Indoor-Outdoor Communication Error — root causes, multimeter test values (Pulsing DC voltage (8V–26V) between N and S...
Godrej AC Error Code E2: Evaporator Coil Frost Sensor Error
Godrej AC Error Code E2: Evaporator Coil Frost Sensor Error — root causes, multimeter test values (10 kΩ at 25°C), step-by-step fix, and on-site repair...
Godrej AC Error Code E1: Room Temperature Sensor Malfunction
Godrej AC Error Code E1: Room Temperature Sensor Malfunction — root causes, multimeter test values (10 kΩ at 25°C across 2-pin indoor PCB header),...
Resolved: Daikin AC U4 Error Code — Immediate Diagnosis & PCB Repair in Vadodara
Resolved: Daikin AC U4 Error Code — Immediate Diagnosis & PCB Repair in Vadodara — root causes, multimeter test values (Restored 15V/5V secondary SMPS...
Daikin AC Error Code U4: Indoor-to-Outdoor Transmission Fault
Daikin AC Error Code U4: Indoor-to-Outdoor Transmission Fault — root causes, multimeter test values (Oscillating 14V–30V DC signal between terminal 2...
Daikin AC Error Code U0: Refrigerant Shortage Warning
Daikin AC Error Code U0: Refrigerant Shortage Warning — root causes, multimeter test values (Discharge thermistor R3T <95°C), step-by-step fix, and...
Daikin AC Error Code L5: Inverter Instantaneous DC Overcurrent
Daikin AC Error Code L5: Inverter Instantaneous DC Overcurrent — root causes, multimeter test values (Diode drop 0.42V–0.52V across all 6 IPM bridge...
Daikin AC Error Code H6: Compressor Position Detection Sensor Fault
Daikin AC Error Code H6: Compressor Position Detection Sensor Fault — root causes, multimeter test values (Balanced winding resistance (0.8 Ω – 2.2 Ω)...
Daikin AC Error Code E4: Low-Pressure Switch Actuation
Daikin AC Error Code E4: Low-Pressure Switch Actuation — root causes, multimeter test values (Continuity across S1PH/LPS switch above 45 PSI),...
Daikin AC Error Code C4: Heat Exchanger Liquid Pipe Thermistor Fault
Daikin AC Error Code C4: Heat Exchanger Liquid Pipe Thermistor Fault — root causes, multimeter test values (20 kΩ at 25°C (Daikin standard NTC curve: ~25...
Daikin AC Error Code A5: Freeze-Up Protector & High-Pressure Control
Daikin AC Error Code A5: Freeze-Up Protector & High-Pressure Control — root causes, multimeter test values (Clean indoor blower wheel CFM), step-by-step...
Carrier AC Error Code EC: Low Refrigerant / Cooling Failure
Carrier AC Error Code EC: Low Refrigerant / Cooling Failure — root causes, multimeter test values (Target coil drop 12°C–16°C below return room air...
Carrier AC Error Code E3: Indoor Blower Fan Speed Out of Control
Carrier AC Error Code E3: Indoor Blower Fan Speed Out of Control — root causes, multimeter test values (310V DC high-voltage rail (BLDC) or 4–6 µF run...
Carrier AC Error Code E1: Indoor-Outdoor Communication Fault
Carrier AC Error Code E1: Indoor-Outdoor Communication Fault — root causes, multimeter test values (Fluctuating 12V–28V DC pulse between Neutral (N) and...
Blue Star AC Error Code F1: Outdoor Ambient Sensor Error
Blue Star AC Error Code F1: Outdoor Ambient Sensor Error — root causes, multimeter test values (10 kΩ – 15 kΩ at 25°C mounted behind outdoor condenser...
Blue Star AC Error Code P4: Inverter IPM & Compressor Drive Trip
Blue Star AC Error Code P4: Inverter IPM & Compressor Drive Trip — root causes, multimeter test values (310V–340V DC across main bus capacitors),...
Blue Star AC Error Code EE: EEPROM Memory Chip Fault
Blue Star AC Error Code EE: EEPROM Memory Chip Fault — root causes, multimeter test values (5.0V DC VCC on pin 8), step-by-step fix, and on-site repair...
Blue Star AC Error Code EC: Refrigerant Leakage Detection
Blue Star AC Error Code EC: Refrigerant Leakage Detection — root causes, multimeter test values (R32 running suction 115–135 PSI | R410A running suction...
Blue Star AC Error Code E3: Evaporator Coil Sensor Fault
Blue Star AC Error Code E3: Evaporator Coil Sensor Fault — root causes, multimeter test values (10 kΩ at 25°C inserted inside evaporator copper sensor...
Blue Star AC Error Code E1: Room Temperature Sensor Fault
Blue Star AC Error Code E1: Room Temperature Sensor Fault — root causes, multimeter test values (10 kΩ at 25°C (typical range 8.5 kΩ – 11.8 kΩ in Vadodara...
Daikin U4 Error Code: Communication Fault
How to diagnose and fix the Daikin U4 error code indicating a communication failure between the indoor and outdoor units.