Mitsubishi Electric Air Conditioning

The upper operation indicator lamp blinks rapidly with 0.5-second intervals of ON and OFF. This signifies a problem with the serial signal communication between the indoor and outdoor units, or potential miswiring.

The unit is operating normally or has no memorized errors. The '00' code indicates that no faults were detected during the last check or operation cycle.

The indoor unit beeps once when accessing the error display mode. This indicates the unit has a stored error, and this particular beep pattern might relate to a specific type of fault.

The indoor unit beeps once when trying to recall error codes. This indicates that the unit has detected an error, and this beep pattern might correspond to a different type or severity of error.

A single red flash from the operation indicator lamp usually points to a problem with the indoor fan motor. This could be a short or open circuit within the motor.

The indoor unit's operation indicator blinks once, indicating a problem with the room temperature thermistor. This means the thermistor may be shorted or open.

The left lamp of the OPERATION INDICATOR blinks once every 0.5 seconds. This indicates that the room temperature thermistor has a short circuit or an open circuit, detected during operation.

An 11-time blink of the operation indicator suggests a problem with the indoor fan motor. The unit may not be receiving the expected feedback signal from the fan during operation.

The left lamp of the OPERATION INDICATOR blinks eleven times, followed by a 2.5-second pause. This indicates that the rotational frequency feedback signal from the indoor fan motor was not emitted for 12 seconds after the fan motor started operation.

The operation indicator blinks 12 times, indicating an issue with the indoor electronic control system. The unit may not be able to read data correctly from its non-volatile memory.

The left lamp of the OPERATION INDICATOR blinks twelve times, followed by a 2.5-second pause. This indicates that the indoor electronic control P.C. board cannot properly read data from its nonvolatile memory.

The upper operation indicator lamp blinks fourteen or more times with a 2.5-second pause. This indicates an unspecified abnormality, possibly related to indoor thermistors or other system components.

The indoor unit beeps twice when attempting to access the error display mode. This confirms that the unit has detected and stored an error code.

The indoor unit beeps twice when trying to recall error codes. This confirms that the unit has detected an error that is stored in its memory.

This blinking pattern typically signifies a communication error between the indoor and outdoor units. It could be due to wiring issues or a fault in one of the units.

The operation indicator on the indoor unit blinks twice. This points to a fault with the indoor coil thermistor, which could be shorted or open.

The upper operation indicator lamp blinks twice with a 2.5-second pause. This indicates a short or open circuit in either the indoor coil thermistor or the room temperature thermistor.

The indoor unit's operation indicator lamp flashes red three times, indicating a communication error. This means the indoor unit cannot communicate with the outdoor unit.

The operation indicator blinks three times, signaling that the indoor unit is not receiving the serial signal from the outdoor unit. This can occur if the signal is lost for an extended period.

The upper operation indicator lamp blinks three times with a 2.5-second pause. This error means the rotational frequency feedback signal is not being detected from the indoor fan motor during operation.

The upper operation indicator lamp blinks four times with a 2.5-second pause. This indicates the indoor electronic control P.C. board cannot properly read data from its non-volatile memory.

The upper operation indicator lamp blinks five times with a 2.5-second pause. This error indicates repeated issues with the outdoor unit's power system, such as overcurrent protection trips or startup failures.

The upper operation indicator lamp blinks six times with a 2.5-second pause. This indicates that one or more thermistors in the outdoor unit have a short or open circuit during compressor operation.

The left lamp of the OPERATION INDICATOR blinks six times. This indicates poor contact in the i-see SENSOR wiring or a failure in loading corrected data for the i-see SENSOR.

This code refers to an A-Control fault, specifically E6 or E8, indicating communication issues between indoor and outdoor units.

This code indicates an A-Control fault, corresponding to E7 or E9 errors, which typically involve communication problems between indoor and outdoor units.

The upper operation indicator lamp blinks seven times with a 2.5-second pause. This error signifies that the outdoor electronic control board or inverter P.C. board cannot properly read data from its memory.

This fault occurs when the system capacity settings exceed the allowed limits, indicated by R2 index exceeding 150% or Y index exceeding 130%.

This error indicates an incorrect capacity setting, often due to misconfiguration of DIP switches on the indoor (SW2) or outdoor (SW5) units.

This fault occurs if there's an error in the number of connected units, often due to loss of M-Net voltage, power issues, or incorrect outdoor box settings.

This error indicates that either the outdoor unit (OC) or the branch controller (BC) has been assigned an incorrect address.

This fault is related to an incorrect attribute setting, specifically SW3-1 on a GUF unit.

The upper operation indicator lamp blinks nine times with a 2.5-second pause. This general error code indicates an abnormality not covered by other specific codes, often related to indoor thermistors.

This error means two or more Lossnay units have been assigned the same address, causing a conflict. Addresses need to be unique.

This fault indicates a hardware error within the transmission processor of a Lossnay unit. Check the communication wiring and the unit's board.

This error means that no data could be transmitted for an extended period (8 minutes), likely due to issues with the M-Net connections.

This fault indicates a communication error with the communication processor, specifically that the Lossnay address is not being transmitted. Check M-Net voltage.

This error means the system is not receiving an acknowledgment (ACK) signal. This could be due to wiring issues, transmission range exceeded, or a faulty converter.

This fault indicates that the M-Net system is not responding. Check wiring, ensure the transmission range is not exceeded, and verify the M-Net converter and wiring type.

The expected amplitude of 10 to 20 V DC is not detected between outdoor terminal block S2 and S3. This measurement is used to confirm the serial signal.

The required 5 VDC power supply is not present between the 5V (+) and GND (-) terminals on the indoor electronic control P.C. board. This indicates a power delivery problem on the board.

The required 9 to 13 VDC power supply is not present between the 12V (+) and GND (-) terminals on the indoor electronic control P.C. board. This points to a power supply problem on the board.

You will hear a single beep from the indoor unit each time it successfully receives a signal from the remote controller. This confirms the remote is communicating with the unit.

A beep tone is heard from the indoor unit when it successfully receives a signal from the remote controller and begins or changes its operation.

During the simple check for the i-see SENSOR (set temperature to 66°F/19°C and place hand over sensor), if the buzzer does not beep at 1-second intervals, it indicates a problem with the sensor or its connection.

The CN10A connector on the indoor electronic control P.C. board or its associated lead wires are disconnected. This disrupts power or signal to the board.

This fault signifies a communication error between the indoor unit and the remote controller. Check wiring, connections, and master/slave settings if applicable.

This code points to a problem with the remote controller, particularly when units are grouped. Addressing issues might be necessary.

These codes indicate a general error with the air conditioner system. The specific meaning can vary and may require referring to detailed service information.

Similar to E1, this error relates to remote controller issues in grouped systems. Ensure correct addressing and wiring, especially in twinned setups.

This error code indicates a transmitting error, often related to refrigerant address settings on the Ecodan system.

This error signifies a receiving error within the PAR W21 system, likely due to incorrect refrigerant address settings on the Ecodan.

Similar to E4, this receiving error usually stems from an incorrect refrigerant address configuration on the Ecodan unit.

This error occurs when the Ecodan unit is powered on before the FTC(2) unit, leading to an indoor/outdoor communication failure.

This error signifies a communication fault between the indoor and outdoor units. It may be related to a condensate pump or issues with the 12/24Vdc power supply.

This fault indicates a communication error between the indoor and outdoor units, typically because the Ecodan was powered up before the FTC(2).

Similar to E6 and E8, this error code signifies an indoor/outdoor communication failure, usually resulting from the Ecodan being powered on before the FTC(2).

This error points to improperly installed or loose connecting cables, or significant electrical noise interference affecting operation.

Similar to EA, this fault suggests issues with wiring or cable specifications, or electrical noise impacting the system.

This error means the unit failed to initialize within the expected time after power-up. Causes include noise interference or incorrect cable specifications.

This fault indicates a serial communication error between the Ecodan's main board and its inverter board, often due to loose cable connections.

The operation indicator lamp blinks seven times. This error occurs when the refrigerant types specified for the indoor and outdoor units do not match.

This is a general error code often caused by electrical noise interference. Power cycling the Ecodan unit may resolve the issue.

There is no electrical conduction (0 Ω resistance) between the connector CN201 on the indoor power P.C. board and S2 on the terminal block. This indicates a break in the wiring path.

This error means the phase rotation of the power supply is incorrect. This can prevent the unit from operating safely.

This fault indicates that the L3 phase of the power supply is not detected. This could be due to an issue with the power supply itself or protective devices.

This error relates to the low-pressure switch (63L) being open. This means the switch is not detecting the expected low-pressure condition.

This fault indicates that the compressor's internal thermostat (49C) has opened, likely due to overheating. This is a safety measure to protect the compressor.

This error code signifies that the high-pressure switch (63H) has opened. This switch is a safety device that trips if system pressure becomes too high.

This indicates a fault within the phase detection circuit, often related to the outdoor unit's control board.

This error means the outdoor unit is not receiving the expected input signals, pointing towards a potentially defective outdoor board.

This fault code indicates that multiple protection devices within the system have triggered an open circuit. This requires checking each device individually.

This code indicates an issue with the 51CM connector, likely an open circuit. It could be due to a thermal relay disconnection or contact failure.

The operation indicator lamp blinks fourteen times, followed by a 3-second ON state. This points to a problem with the refrigerant sensor on the indoor unit.

The operation indicator lamp blinks fourteen times, followed by a 3-second ON state. This indicates a refrigerant leak detected by the sensor.

The operation indicator lamp blinks twelve times. This means the indoor electronic control board cannot properly read data from its non-volatile memory.

A blown fuse (F11) suggests an electrical issue within the indoor unit's control board. This often accompanies problems with the fan motor or electronic components.

Only the fuse (F11) on the indoor power P.C. board has blown. This could indicate a problem with the indoor fan motor or the electronic control P.C. board.

A blinking green LED on the Wireless LAN module indicates that it is trying to establish a connection to the Wi-Fi network. This is a normal status during network setup or reconnection.

When you turn on the power supply and press the emergency operation switch, the left lamp of the OPERATION INDICATOR on the indoor unit does not light up. This indicates that the indoor unit is not receiving electrical power.

The indoor and outdoor units will not operate. This indicates the serial signal from the outdoor unit has not been received for 6 minutes. Check for wiring issues or signal interruptions.

An abnormality other than the listed codes is detected, potentially related to indoor or ambient temperature thermistors. Do not restart operation without repair.

The left lamp of the OPERATION INDICATOR blinks fourteen times or more, followed by a 2.5-second pause. This signifies an abnormality in the outdoor unit not covered by other specific codes.

The left lamp of the OPERATION INDICATOR blinks two times, followed by a 2.5-second pause. This indicates a short or open circuit in either the indoor coil thermistor or the room temperature thermistor.

This blinking pattern means the indoor coil or room temperature thermistor is experiencing a short or open circuit. The unit will not operate.

The left lamp of the OPERATION INDICATOR blinks three times, followed by a 2.5-second pause. This indicates that the rotational frequency feedback signal was not emitted during the indoor fan operation.

This indicates that the rotational frequency feedback signal is not being emitted during indoor fan operation. The unit will not run.

The left lamp of the OPERATION INDICATOR blinks four times, followed by a 2.5-second pause. This signifies that the indoor electronic control P.C. board cannot properly read data in its nonvolatile memory.

The system cannot properly read data from the non-volatile memory of the indoor electronic control P.C. board. The unit will not operate.

The left lamp of the OPERATION INDICATOR blinks five times, followed by a 2.5-second pause. This means the compressor stopped three consecutive times within one minute after startup due to overcurrent protection or startup failure protection.

This occurs if the compressor stops due to overcurrent or startup failure protection three times within one minute of startup. The unit will not operate.

The left lamp of the OPERATION INDICATOR blinks six times, followed by a 2.5-second pause. This indicates a short or open circuit in the outdoor thermistors during compressor operation.

The outdoor thermistors have a short or open circuit during compressor operation. The unit will not run.

The left lamp of the OPERATION INDICATOR blinks seven times, followed by a 2.5-second pause. This indicates that the inverter P.C. board or the outdoor electronic control P.C. board cannot properly read data in its nonvolatile memory.

The system cannot properly read data from the non-volatile memory of the inverter P.C. board or the outdoor electronic control P.C. board. The unit will not operate.

The left lamp of the OPERATION INDICATOR lamp lights up continuously (solid), and the outdoor unit does not operate. This indicates that the inverter P.C. board or the outdoor electronic control P.C. board cannot properly read data in its nonvolatile memory.

This code indicates a general or unspecified abnormality detected in the outdoor unit that does not fit other specific error codes.

This indicates a problem with the room temperature thermistor or the indoor coil thermistor. The unit may not operate normally.

This indicates a problem with the indoor fan motor. The unit may not operate normally.

This indicates a fault within the indoor unit's control system, likely related to its electronic control P.C. board. The unit may not operate normally.

This indicates a problem with the outdoor unit's power system. It may be due to compressor overcurrent protection or startup failure protection.

This indicates a fault with the thermistors in the outdoor unit. These sensors are crucial for temperature monitoring during compressor operation.

This indicates a fault within the outdoor unit's control system, possibly related to its P.C. board memory. The unit may not operate normally.

This indicates a problem with the connection or signal between the indoor and outdoor units. The indoor unit may not operate when the EMERGENCY OPERATION switch is pressed.

The left (or upper) lamp on the Operation Indicator blinks continuously at 0.5-second intervals. This signifies an abnormality within the indoor unit.

The indoor and outdoor units are not communicating. The serial signal from the outdoor unit has not been received for 6 minutes. The indoor unit and outdoor unit may not operate.

An abnormality has been detected that does not fall into the other specific categories. This requires further investigation.

The indoor coil temperature thermistor or the room temperature thermistor has a short or open circuit. The unit may not operate correctly.

The indoor fan motor is not sending a rotational frequency feedback signal during operation. This means the fan might not be spinning correctly or at all.

The system cannot properly read data from the non-volatile memory of the indoor electronic control P.C. board. This indicates a problem with the indoor unit's main circuit board.

The outdoor unit's power system has detected an issue. This occurs if the compressor protection (overcurrent or startup failure) trips 3 times within 1 minute of startup.

One or more thermistors in the outdoor unit have a short or open circuit while the compressor is running. This affects temperature sensing.

The system cannot properly read data from the non-volatile memory of the outdoor inverter P.C. board or the outdoor electronic control P.C. board.

The outdoor unit does not operate because the system cannot properly read data from the non-volatile memory of the inverter P.C. board.

The left (or upper) lamp on the Operation Indicator stays on for 3 seconds without any beeps. This indicates an abnormality with the outdoor unit.

When attempting to check the error code display mode, the indoor unit does not beep. This suggests that no relevant errors are currently stored or detectable by this mode, or there might be interference.

When attempting to recall error codes, the indoor unit does not beep. This usually means the diagnosis process failed, the remote controller batteries are low, or there are no errors stored that match the recall function.

The unit is not receiving the correct voltage from the main power source. This could be due to a tripped breaker, a power outage, or an issue with the electrical supply.

The left lamp of the OPERATION INDICATOR on the indoor unit stays ON for 3 seconds (without a beep) before starting to blink at 0.5-second intervals. This specific pattern indicates an abnormality in the outdoor unit.

The left lamp of the OPERATION INDICATOR on the indoor unit blinks quickly, with a beep at the same timing as the blink. This indicates a general abnormality in either the indoor or outdoor unit.

When recalling failure modes, if the left lamp of the OPERATION INDICATOR blinks at 0.5-second intervals with beeps, this points to an abnormality within the indoor unit. This pattern helps identify the specific problem.

When recalling failure modes, if the left lamp of the OPERATION INDICATOR blinks at 0.5-second intervals with no beep, this indicates an abnormality in the outdoor unit. This pattern helps identify the specific problem.

This blinking light can mean the unit is getting closer to the set temperature. It may also indicate standby mode, particularly in multi-system setups where different indoor units are operating. The blink rate can vary.

The air conditioner is actively running to adjust the room temperature to your desired setting. This light indicates normal operation is in progress.

When the lamp is not lit, the air conditioner is typically turned off or is in a normal standby state. No active cooling or heating is occurring.

The operation indicator lamp on the indoor unit is blinking on and off. This indicates that the air conditioner is experiencing an abnormal condition.

When the operation indicator lamp is steadily lit, it signifies that the air conditioning unit is currently running to reach the set temperature.

When the operation indicator lamp is not lit, the unit is either turned off or in standby mode. In multi-system operations, it might indicate standby status.

The LED on the outdoor control P.C. board is lit, which indicates abnormal communication or that the unit is not connected. This differs from normal blinking.

The LED on the outdoor control P.C. board repeats a specific blinking pattern (3.6 seconds off, 0.8 seconds on). This pattern typically indicates an issue with the indoor/outdoor connecting wire.

This error indicates a fault with the flow temperature sensor (TH1). It may be disconnected, short-circuited, or have an open circuit.

This fault is related to the liquid pipe thermistor (TH2), indicating it may be disconnected, have an open circuit, or a short circuit.

This error indicates an issue with the drain sensor (DS), reporting an open or short circuit. This sensor monitors the condensate drain.

This fault means the unit has detected a high level of condensate water, usually due to a drain pump failure or a blockage in the drain line.

This indicates the indoor unit's heat exchanger is either freezing (in cooling mode) or overheating (in heating mode). This is typically caused by restricted airflow through the indoor coil.

This fault suggests an abnormal temperature reading in the refrigerant pipes. The most common cause is a refrigerant leak, but incorrect thermistor placement can also be a factor.

This fault indicates an issue with the TH5 thermistor, which monitors the condenser or evaporator temperature. It may be disconnected or have an open/short circuit.

The operation indicator lamp blinks eleven times. This indicates that the indoor fan motor is not emitting a rotational frequency feedback signal after it should have started.

The expected rated voltage is not detected between the outdoor terminal block S1 and S2. This indicates a problem with the incoming power supply or the wiring to the unit.

The remote controller may not operate correctly if the batteries are weak, leaking, or if its internal microcomputer needs a reset. This can prevent you from controlling your air conditioner.

A resistance reading of 1 Megaohm or higher for the indoor fan motor indicates an open circuit, meaning the motor is not functioning electrically.

Measuring the resistance of the indoor fan motor and getting a reading of approximately 4 Ohms indicates that the motor coil is likely functioning correctly.

The resistance measurement of the indoor fan motor is very high (1MΩ or more), indicating an open circuit. This could be the motor itself or the fuse.

The resistance of the reactor L111 on the indoor power P.C. board is not approximately 4.3 ohms. This suggests a fault with the reactor or the associated circuitry on the board.

The resistance of resistor R111 on the indoor power P.C. board is not approximately 4 ohms. This indicates a fault with the resistor or the board itself.

After restarting the power or using the emergency operation switch, the system indicates a serial signal error, usually after about 6 minutes. This suggests a problem with communication between the indoor and outdoor units, or interference from external devices.

A serial signal error is indicated after 6 minutes of operation. This suggests a communication problem between the indoor and outdoor units or an issue with the connecting wires.

This error indicates a high-pressure condition within the system, which can be caused by several factors including outdoor fan failure or blockages.

This fault indicates excessively high discharge temperature, often due to insufficient refrigerant, a faulty thermistor, or high ambient operating conditions.

This error points to a fault with the discharge thermistor (TH4), indicating it might be open, shorted, or disconnected.

This fault indicates a problem with an outdoor thermistor (specific sensor not detailed here, but likely related to ambient or operational temperature).

This error means the inverter's heat sink temperature (TH8) is too high. This is usually due to insufficient airflow or a faulty thermistor.

This fault indicates the compressor is drawing too much current. This requires electrical checks of the compressor and inverter output.

This error suggests the discharge superheat is too low, meaning the refrigerant may not be properly absorbing heat. Check the TH4 reading and LEV operation.

The upper lamp blinks twice, followed by the lower lamp lighting up. This points to an issue with the refrigerant sensor itself.

The upper lamp blinks three times, and then the lower lamp turns on. This combination indicates a refrigerant leak has been detected by a sensor.

The indoor and outdoor units will not operate. This indicates the serial signal from the outdoor unit has not been received for 6 minutes. Check for wiring issues or signal interruptions.

An abnormality other than the listed codes is detected, potentially related to indoor or ambient temperature thermistors. Do not restart operation without repair.

This symptom indicates a problem with the refrigerant sensor on the indoor unit. It might be disconnected or have a broken wire. The fan may operate, but the unit cannot be controlled by the remote.

This blinking pattern means the indoor coil or room temperature thermistor is experiencing a short or open circuit. The unit will not operate.

This indicates a potential refrigerant leak detected by the sensor. The unit may emit a buzzer sound, and the fan will operate for an extended period. It cannot be controlled by the remote.

This indicates that the rotational frequency feedback signal is not being emitted during indoor fan operation. The unit will not run.

The system cannot properly read data from the non-volatile memory of the indoor electronic control P.C. board. The unit will not operate.

This occurs if the compressor stops due to overcurrent or startup failure protection three times within one minute of startup. The unit will not operate.

The outdoor thermistors have a short or open circuit during compressor operation. The unit will not run.

The system cannot properly read data from the non-volatile memory of the inverter P.C. board or the outdoor electronic control P.C. board. The unit will not operate.

This indicates that the indoor unit's operation mode is set differently from other indoor units in a multi-system setup. The first unit set has priority. Other units may not operate.

The outdoor unit operates, but the indoor unit does not. This happens when indoor units are set to conflicting modes like COOL (including DRY) and HEAT simultaneously. The first unit to operate sets the priority.

The outdoor unit does not operate because the system cannot properly read data from the non-volatile memory of the inverter P.C. board or the outdoor electronic control P.C. board.

Both the varistor and the fuse on the indoor power P.C. board have failed. This suggests a significant electrical issue within the indoor unit's power supply.