Mitsubishi Electric air conditioning systems are renowned for their ultra-quiet operation and cost-effective performance, offering significant savings on both installation and running costs.
Mitsubishi Electric Error Codes List:
City Multi Systems:
- 403:Communications fault between boards. Check the inverter error details to identify the specific boards involved, and inspect the transformer, bus voltage, and interconnecting cables.
- 900:The Lossnay unit is in a test run.
- 1102:Compressor discharge temperature is too high (exceeded 110°C). This may indicate a refrigerant shortage or a discharge thermistor issue.
- 1301:Low pressure fault detected before starting. Inspect thermistors (TH2, TH3, TH4), refrigerant charge, indoor fan, heat exchanger, and filters.
403:Communications fault between boards. Check the inverter error details to identify the specific boards involved, and inspect the transformer, bus voltage, and interconnecting cables.
900:The Lossnay unit is in a test run.
1102:Compressor discharge temperature is too high (exceeded 110°C). This may indicate a refrigerant shortage or a discharge thermistor issue.
1301:Low pressure fault detected before starting. Inspect thermistors (TH2, TH3, TH4), refrigerant charge, indoor fan, heat exchanger, and filters.
Mr. Slim P Series (A-Control):
- A0:Green LED – 2 flashes, Red LED – 5 flashes, Controller 6600: Lossnay units have the same address. Change the addresses and reset the unit.
- A2:Green LED – 2 flashes, Red LED – 5 flashes, Controller 6602: Transmission processor hardware error. Check communications wiring and the Lossnay board for faults.
- A6:Green LED – 2 flashes, Red LED – 5 flashes, Controller 6606: Communication error with the communication processor. Check the M-Net voltage.
- E0:Green LED – 2 flashes, Red LED – 3 flashes: Communication error with the remote controller. Verify wiring, voltage, and connections. If multiple systems are connected, check the master/slave settings.
A0:Green LED – 2 flashes, Red LED – 5 flashes, Controller 6600: Lossnay units have the same address. Change the addresses and reset the unit.
A2:Green LED – 2 flashes, Red LED – 5 flashes, Controller 6602: Transmission processor hardware error. Check communications wiring and the Lossnay board for faults.
A6:Green LED – 2 flashes, Red LED – 5 flashes, Controller 6606: Communication error with the communication processor. Check the M-Net voltage.
E0:Green LED – 2 flashes, Red LED – 3 flashes: Communication error with the remote controller. Verify wiring, voltage, and connections. If multiple systems are connected, check the master/slave settings.
Mr. Slim P Series (K-Control):
- E0:System transmission error. There could be a communication fault between the indoor and remote controllers.
- P4:Drain sensor fault. Check the drain sensor resistance and connections.
- P5:Drain fault. High levels of condensate detected; inspect for blockages in the drain, tray, or possible pump failure.
- P7:System error due to an address setting fault.
E0:System transmission error. There could be a communication fault between the indoor and remote controllers.
P4:Drain sensor fault. Check the drain sensor resistance and connections.
P5:Drain fault. High levels of condensate detected; inspect for blockages in the drain, tray, or possible pump failure.
P7:System error due to an address setting fault.
Additional Common Error Codes:
- P1:Intake sensor error.
- P2 – P9:Pipe (liquid or 2-phase) sensor error.
- E6 – E7:Indoor/outdoor unit communication error.
- PA:Forced compressor error.
- P6:Freezing/overheating safeguard operation.
- EE:Communication error between indoor and outdoor units.
- P8:Pipe temperature error.
- E4:Remote controller signal receiving error.
- Fb:Indoor unit control system error (memory error, etc.).
- E1 – E3:Remote controller transmission error.
- E9:Indoor/outdoor unit communication error (transmitting error) in the outdoor unit.
- UP:Compressor overcurrent interruption.
- U3 – U4:Open/short circuit of outdoor unit thermistors.
- UF:Compressor overcurrent interruption (when compressor is locked).
- U2:Abnormal high discharging temperature or insufficient refrigerant.
- U1 – Ud:Abnormal high pressure or overheating safeguard operation.
- U5:Abnormal temperature of heat sink.
- U8:Outdoor unit fan safeguard stop.
- U6: Compressor overcurrent interruption
P1:Intake sensor error.
P2 – P9:Pipe (liquid or 2-phase) sensor error.
E6 – E7:Indoor/outdoor unit communication error.
PA:Forced compressor error.
P6:Freezing/overheating safeguard operation.
EE:Communication error between indoor and outdoor units.
P8:Pipe temperature error.
E4:Remote controller signal receiving error.
Fb:Indoor unit control system error (memory error, etc.).
E1 – E3:Remote controller transmission error.
E9:Indoor/outdoor unit communication error (transmitting error) in the outdoor unit.
UP:Compressor overcurrent interruption.
U3 – U4:Open/short circuit of outdoor unit thermistors.
UF:Compressor overcurrent interruption (when compressor is locked).
U2:Abnormal high discharging temperature or insufficient refrigerant.
U1 – Ud:Abnormal high pressure or overheating safeguard operation.
U5:Abnormal temperature of heat sink.
U8:Outdoor unit fan safeguard stop.
U6: Compressor overcurrent interruption
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Written by
Ali Elm
Ali is the Head of Operations at Be Cool Refrigeration with over a decade of hands-on experience in HVAC and commercial refrigeration. He oversees every installation, repair, and maintenance project, making sure the work meets the highest standards. Ali holds full F-Gas certification and has worked across residential, commercial, and industrial refrigeration systems throughout London and the South East. When he is not on site, he writes these guides to help business owners and homeowners understand their cooling systems better.