Mitsubishi Electric Air Conditioners
40 fault codes documented
Outdoor Unit Recall: 1-time blink - Indoor/outdoor communication, receiving error
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks once, then stays OFF for 2.5 seconds. This indicates that normal signals cannot be received from the inverter P.C. board for 3 minutes, or incorrect signals were received consistently.
1-time blink 2.5 seconds OFF — Frequency drop by current protection (Outdoor unit operates)
The outdoor unit LED blinks 1 time with a 2.5-second pause, and the unit is still operating. This indicates the compressor frequency has lowered because the input current exceeded approximately 10A. This is a normal protective operation, but underlying conditions may need checking. For MUZ-AP71, the current from the power outlet is nearing breaker capacity.
1-time blink every 2.5 seconds — Outdoor unit overcurrent protection
The outdoor unit's overcurrent protection has activated three times within one minute after the compressor started. The outdoor unit LED blinks once with a 2.5-second pause.
10-time blink 2.5 seconds OFF — Outdoor fan motor fault
The outdoor unit LED blinks 10 times with a 2.5-second pause. This indicates that the outdoor fan has stopped three times consecutively within 30 seconds of starting.
Outdoor Unit Recall: 11-time blink - Compressor synchronous abnormality
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks eleven times, then stays OFF for 2.5 seconds. This indicates a compressor start-up failure protection has activated due to a distorted waveform of the compressor current.
11-time blink 2.5 seconds OFF — Stop valve detected closed
The outdoor unit LED blinks 11 times with a 2.5-second pause. This indicates that a closed stop valve has been detected based on the compressor current.
Outdoor Unit Recall: 12-time blink - Compressor synchronous abnormality
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks twelve times, then stays OFF for 2.5 seconds. This indicates a compressor start-up failure protection has activated due to a distorted waveform of the compressor current.
12-time blink 2.5 seconds OFF — Compressor phase current abnormality
The outdoor unit LED blinks 12 times with a 2.5-second pause. This indicates that each phase current of the compressor cannot be detected normally.
13-time blink 2.5 seconds OFF — Bus-bar voltage (DC) detection abnormality
The outdoor unit LED blinks 13 times with a 2.5-second pause. This indicates that the bus-bar voltage of the inverter cannot be detected normally. This can happen due to instantaneous power voltage drops or short-time power failures, especially for MUZ-AP71 models.
14-time blink 2.5 seconds OFF — Outdoor unit general abnormality
The outdoor unit LED blinks 14 times with a 2.5-second pause. This signals a general defect or other abnormality within the outdoor unit.
16-time blink 2.5 seconds OFF — 4-way valve or pipe temperature issue
The outdoor unit LED blinks 16 times with a 2.5-second pause. This indicates that the 4-way valve is not working correctly, or the indoor coil thermistor has detected an abnormal temperature.
17-time blink 2.5 seconds OFF — Outdoor refrigerant system abnormality
The outdoor unit LED blinks 17 times with a 2.5-second pause. This indicates a problem in the outdoor refrigerant system, such as a closed valve or air trapped in the circuit. This is detected by thermistor readings and compressor current.
Outdoor Unit Recall: 2-time blink - Outdoor heat exchanger temperature thermistor fault
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks twice, then stays OFF for 2.5 seconds. This pattern signifies a short circuit or an open circuit in the outdoor heat exchanger temperature thermistor.
2-time blink 2.5 seconds OFF — Outdoor unit overcurrent protection repeated
The outdoor unit LED blinks 2 times with a 2.5-second pause. The unit stops and restarts 3 minutes later, repeatedly, due to overcurrent protection (large current flowing into the power module).
Outdoor Unit Recall: 3-time blink - P.C. board temperature thermistor fault
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks three times, then stays OFF for 2.5 seconds. This specific pattern indicates a short circuit or an open circuit in the P.C. board temperature thermistor.
3-time blink 2.5 seconds OFF — Discharge temperature overheat protection
The outdoor unit LED blinks 3 times with a 2.5-second pause. This indicates that the discharge temperature thermistor exceeded 116°C, causing the compressor to stop. The compressor can restart when the temperature drops below 100°C.
3-time blink 2.5 seconds OFF — Frequency drop by high pressure protection (Outdoor unit operates)
The outdoor unit LED blinks 3 times with a 2.5-second pause, and the unit is still operating. This indicates the compressor frequency has lowered because the indoor coil thermistor exceeded 55°C in HEAT mode.
Outdoor Unit Recall: 4-time blink - Overcurrent detected
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks four times, then stays OFF for 2.5 seconds. This indicates a large current flow into the power module (IC700).
4-time blink 2.5 seconds OFF — Fin/P.C. board temperature overheat protection
The outdoor unit LED blinks 4 times with a 2.5-second pause. This means the fin temperature thermistor on the heat sink or the P.C. board temperature thermistor on the inverter P.C. board has exceeded its safe operating temperature (e.g., 75-86°C).
4-time blink 2.5 seconds OFF — Frequency drop by defrosting in COOL mode / discharge temperature protection (Outdoor unit operates)
The outdoor unit LED blinks 4 times with a 2.5-second pause, and the unit is still operating. This indicates the compressor frequency has lowered because the indoor coil thermistor read 8°C or less in COOL mode (defrosting), or the discharge temperature thermistor exceeded 111°C (discharge temperature protection).
Outdoor Unit Recall: 5-time blink - Nonvolatile memory data error
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks five times, then stays OFF for 2.5 seconds. This indicates that the nonvolatile memory data on the inverter P.C. board cannot be read properly.
5-time blink 2.5 seconds OFF — High pressure protection
The outdoor unit LED blinks 5 times with a 2.5-second pause. This indicates high pressure protection activated because the indoor coil thermistor exceeded 70°C in HEAT mode, or the defrost thermistor exceeded 70°C in COOL mode.
5-time blink 2.5 seconds OFF — Outside temperature thermistor protection (Outdoor unit operates)
For MUZ-AP25/35/42 models, the outdoor unit LED blinks 5 times with a 2.5-second pause, and the unit is still operating. This indicates that the outside temperature thermistor has shorted or opened, and the unit is performing a protective operation without that thermistor.
Outdoor Unit Recall: 6-time blink - Power module or compressor winding short circuit
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks six times, then stays OFF for 2.5 seconds. This indicates an interface short circuit in the output of the power module (IC700) or a short circuit within the compressor winding itself.
6-time blink 2.5 seconds OFF — Serial communication failure
The outdoor unit LED blinks 6 times with a 2.5-second pause. This indicates that communication has failed between the indoor and outdoor units for 3 minutes.
Outdoor Unit Recall: 7-time blink - Fin or P.C. board over-temperature
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks seven times, then stays OFF for 2.5 seconds. This indicates an over-temperature condition on either the fin temperature thermistor or the P.C. board temperature thermistor of the inverter P.C. board.
7-time blink 2.5 seconds OFF — Low discharge temperature protection
The outdoor unit LED blinks 7 times with a 2.5-second pause. This indicates that the discharge temperature thermistor has read 50°C or less for 20 minutes, triggering low discharge temperature protection.
Outdoor Unit Recall: 8-time blink - Outdoor fan motor fault
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks eight times, then stays OFF for 2.5 seconds. This indicates that the outdoor fan has stopped 3 times consecutively within 30 seconds after it initially started up.
8-time blink 2.5 seconds OFF — PAM protection / Zero cross detecting circuit issue
The outdoor unit LED blinks 8 times with a 2.5-second pause. For MUZ-AP25/35/42/50/60 models, this indicates PAM protection due to overcurrent in PFC or high bus-bar voltage (394V+). For MUZ-AP71, it indicates the zero cross signal cannot be detected. Both can be caused by instantaneous power voltage drops or distortion of primary voltage.
Outdoor Unit Recall: 9-time blink - Nonvolatile memory data error
When the outdoor unit failure mode recall function is active, the indoor unit's upper lamp blinks nine times, then stays OFF for 2.5 seconds. This indicates that the nonvolatile memory data on the inverter P.C. board cannot be read properly.
9-time blink 2.5 seconds OFF — Inverter check mode (Compressor disconnected)
The outdoor unit LED blinks 9 times with a 2.5-second pause. This indicates that the inverter check mode has started because the compressor's connector is disconnected.
Outdoor unit abnormal - Indoor lamp stays ON for 3 seconds without beep
Before any blinking, the upper lamp on the indoor unit stays ON for 3 seconds without emitting a beep. This indicates an abnormality within the outdoor unit. Further steps are needed to determine the specific fault.
Indoor unit abnormal - Lamp blinks 0.5-second interval with beep
The upper lamp on the indoor unit blinks at a 0.5-second interval, accompanied by a beep. This indicates an abnormality within the indoor unit. Further investigation using the recall function or a specific indoor unit service manual is needed to pinpoint the exact issue.
Indoor unit 10-time blink — Low discharge temperature protection (Recall Function)
The indoor unit's upper lamp blinks 10 times, indicating that the discharge temperature thermistor has been 50°C or less for 20 minutes, triggering low discharge temperature protection.
Indoor unit 11-time blink, Outdoor unit 8-time blink — Bus-bar voltage (DC) abnormality (Recall Function)
The indoor unit's upper lamp blinks 11 times and the outdoor P.C. board LED blinks 8 times. This indicates that the bus-bar voltage of the inverter cannot be detected normally.
Indoor unit 14-time blink, Outdoor unit 14-time blink — Stop valve detected closed (Recall Function)
The indoor unit's upper lamp blinks 14 times and the outdoor P.C. board LED blinks 14 times. This indicates that a closed stop valve has been detected based on the compressor current.
Indoor unit 16-time blink, Outdoor unit 1-time blink — Outdoor refrigerant system abnormality (Recall Function)
The indoor unit's upper lamp blinks 16 times and the outdoor P.C. board LED blinks 1 time. This indicates a problem in the outdoor refrigerant system, such as a closed valve or air trapped in the circuit. This is detected based on temperature sensed by thermistors and compressor current.
Indoor unit 7-time blink — Outdoor unit nonvolatile memory error
The upper lamp of the indoor unit's OPERATION INDICATOR blinks 7 times. This indicates that the outdoor control system cannot properly read its nonvolatile memory data.
Indoor unit 9-time blink, Outdoor unit 9-time blink — Compressor phase current abnormality (Recall Function)
The indoor unit's upper lamp blinks 9 times and the outdoor P.C. board LED blinks 9 times. This indicates that each phase current of the compressor cannot be detected normally.
Outdoor unit does not operate — Outdoor thermistor fault detected
The outdoor unit is not operating due to a detected short or open circuit in one of the outdoor temperature thermistors. This includes thermistors for discharge temperature, fin temperature, defrost, P.C. board temperature, outdoor heat exchanger, or ambient temperature.