Error Codes and Troubleshooting for Mitsubishi Electric Air Conditioners
| 0403 | Serial communication error |
| 0900 | Test run |
| 1102 | Discharge temperature fault |
| 1301 | Low pressure fault |
| 1302 | High pressure fault |
| 1500 | Refrigerant overcharge |
| 2500 | Drain sensor submergence |
| 2502 | Drain pump fault |
| 2503 | Drain sensor fault |
| 2600 | Water leak |
| 4102 | Open phase |
| 4106 | Transmission power supply fault |
| 4115 | Power supply signal sync error |
| 4116 | RPM error/Motor error |
| 4220 | Abnormal bus voltage |
| 4225 | Low bus voltage |
| 4230/4260 | Heatsink overheat protection activated |
| 4240 | Overload protection activated |
| 4250 | Overcurrent protection activated |
| 4255 | Outdoor unit fan error |
| 5101 | Temperature sensor fault |
| 5102 | Return air thermistor fault |
| 5110 | Outdoor unit inverter heatsink thermistor error |
| 5201 | Pressure sensor fault |
| 5301 | Current sensor fault |
| 5701 | Loose float switch |
| 6201 | Remote controller issue |
| 6600 | Address overlap |
| 6601 | Polarity setting error |
| 6602 | Transmission processor hardware error |
| 6603 | Transmission line busy |
| 6606 | Communication fault |
| 6607 | No ACK |
| 6608 | No response |
| 6831/6834 | MA controller signal reception error |
| 6832/6833 | MA controller comms fault |
| 7100 | Total capacity error |
| 7101 | Capacity code setting error |
| 7102 | Wrong number of connected units |
| 7105 | Address setting error |
| 7106 | Attribute setting error |
| 7110 | Signal transmission error |
| 7111 | Remote controller sensor fault |
| 7113 | Function setting error |
| 7117 | Model setting error |
| 7130 | Incompatible unit combination |
General Mitsubishi Electric Air Conditioner Error Codes
| Error Code Number and Letter | Air Conditioner Fault Description |
|---|---|
| P1 | Intake sensor error |
| P2 P9 | Pipe (Liquid or 2-phase pipe) sensor error |
| E6 E7 | Indoor/outdoor unit communication error |
| P4 | Drain sensor error |
| P5 | Drain pump 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.) |
| E0 E3 | Remote controller transmission error |
| E1 E2 | Remote controller control board error |
| E9 | Indoor/outdoor unit communication error (Transmitting error) (Outdoor unit) |
| UP | Compressor overcurrent interruption |
| U3, U4 | Open/short of outdoor unit thermistors |
| UF | Compressor overcurrent interruption (When compressor locked) |
| U2 | Abnormal high discharging temperature/49C worked/insufficient refrigerant |
| U1 Ud | Abnormal high pressure (63H worked)/Overheating safeguard operation |
| U5 | Abnormal temperature of heat sink |
| U6 | Compressor overcurrent interruption/Abnormal of power module |
| U7 | Abnormality of superheat due to low discharge temperature |
| U8 | Outdoor unit fan safeguard stop |
| U9 | UH Abnormality such as overvoltage or voltage shortage and abnormal synchronous signal to the main circuit/ Current sensor error. |
Mitsubishi Electric Air Conditioner Error Codes
| Error Code Number and Letter | Air Conditioner Fault Description |
|---|---|
| EA | Error detail Miswiring of indoor/outdoor unit. exceed the number of indoor unit connections. |
| EB | Error detail Miswiring of indoor/outdoor unit. (miswiring disconnection) |
| EC | Error detail Start-up time over |
| E6 | Error detail Indoor/outdoor unit transmission error (signal receiving error) |
| E7 | Error detail Indoor/outdoor unit transmission error (transmitting error) |
| E8 | Error detail Indoor/outdoor unit transmission error (signal receiving error) |
| E9 | Error detail Indoor/outdoor unit transmission error (transmitting error) |
| E0 | Error detail Remote control transmission error (signal receiving error) |
| E3 | Error detail Remote control transmission error (transmitting error) |
| E4 | Error detail Remote control transmission error (signal receiving error) |
| E5 | Error detail Remote control transmission error (transmitting error) |
| EF | Error detail M-NET transmission error |
| ED | Error detail Serial transmission error |
| P1 | Error detail Abnormality of room temperature thermistor (TH1) |
| P2 | Error detail Abnormality of pipe temperature thermistor/liquid (TH2) |
| P4 | Error detail Abnormality of drain sensor (DS) |
| P5 | Error detail Malfunction of drain-up machine |
| P6 | Error detail Freezing/overheating protection detect |
| P8 | Error detail Abnormality of pipe temperature |
| P9 | Error detail Anormality of pipe temperature thermistor/condenser/evaporator (TH5) |
| F1 | Error detail Reverse phase detection |
| F2 | Error detail L3 open phase detection |
| F3 | Error detail 63L connector open |
| F4 | Error detail 49C connector open |
| F7 | Error detail Reverse phase detection circuit (p.c.board) fault |
| F8 | Error detail Input circuit fault |
| F9 | Error detail Connector 2 or more open |
| FA | Error detail L2-phased open phase or 51CM connector open |
| U2 | Error detail Abnormal high discharging temperature |
| U2 | Error detail Inner thermostat (49C) operation |
| U1 | Error detail Abnormal high pressure (high pressure swicth 63H worked) |
| U1 | Error detail Direct cut operation |
| UE | Error detail High pressure error (ball valve closed) |
| UL | Error detail Abnormal low pressure |
| UD | Error detail Overheat protection |
| U6 | Error detail Compressor over current (overload) cut off |
| UA | Error detail Compressor over current (terminal relay operation) |
| UF | Error detail Compressor over current (start-up locked) cut off |
| UF | Error detail Compressor over current (operating locked) cut off |
| UH | Error detail Current sensor error |
| U3 | Error detail Discharge thermistor short/open |
| U4 | Error detail Outdoor thermistor short/open |
| Mr.Slim K-control | Display of remote controller |
| LED E0 | Diagnosis of malfunction Transmitting/receiving signal error |
| LED P1 | Diagnosis of malfunction Intake air sensor abnormal |
| LED P2 | Diagnosis of malfunction Pipe sensor abnormal |
| LED P3 | Diagnosis of malfunction System error (transmitting/receiving signal) |
| LED P4 | Diagnosis of malfunction Drain sensor abnormal |
| LED P5 | Diagnosis of malfunction Malfunctioning of the drain overflow protecting mechanism |
| LED P6 | Diagnosis of malfunction Abnormality of the coil frost/overheating protection mode |
| LED P7 | Diagnosis of malfunction System error (address) |
| LED P8 | Diagnosis of malfunction Outdoor unit malfunction |
| Mr.Slim K-control | PUH-EK Outdoor unit |
| LED ON | Operation status |
| LED Flash | Check code display |
| LED LD1 | LED ON Compressor directive LED Flash Reverse phase detect |
| LED LD2 | LED ON Heating directive LED Flash Open phase detect |
| LED LD3 | LED ON During 63H1 operation LED Flash Pipe sensor short/open |
| LED LD4 | LED ON Compressor ON LED Flash High pressure switch (63H2) operation |
| LED LD5 | LED ON Outdoor fan ON LED Flash Over current relay (51CM) operation |
| LED LD6 | LED ON 4-way valve ON LED Flash Thermal switch (26C) operation |
| LED LD7 | LED ON Bypass valve ON LED Flash Thermistor (TH3) overheat protection |
| LED LD8 | LED ON Crankcase heater ON LED Flash Defective input |
Mitsubishi Electric Air Conditioner Error Codes
| Error Code Letter and Number | Air Conditioner Fault Description |
|---|---|
| EO | During individual unit control: Bad contact of transmission wire Signal transmitting/receiving circuits are abnormal |
| P1 | Bad contact with the thermistor Damaged thermistor |
| P2 | Bad contact with the thermistor Damaged thermistor |
| P3 | Bad contact of transmission wire Signal transmitting/receiving circuits are abnormal Wrong operation due to noise wave emitted by other appliances |
| P4 | Bad contact of transmission wire Damaged thermistor |
| P5 | Malfunction of the drain pump Damaged drain sensor |
| P6 | Short cycle of air cycle Dirty air filter Damaged fan Abnormal refrigerant |
| P7 | Wrong address-setting Signal transmitting/receiving circuit of the remote controller is abnormal Wrong SW6-setting |
| P8 | Wrong wiring of indoor/outdoor connecting wire Reversed phase The protection device is working Damaged outdoor coil thermistor |
Mitsubishi Electric Air Conditioner Not Heating
First check all the not cooling issues as these are interchangable.
| Problem | Treatment |
|---|---|
| Standby showing on control panel | The air conditioner must warm up the coils when it is set to heating mode. This is standard functioning, and it lasts for around five to ten minutes after which the device starts heating normally. While the equipment is on standby, do not switch it off as this will just prolong the procedure. |
| Defrost or Standby showing on control panel | The temperature of the external coil in a heat pump system can drop significantly while it is heating. Frost can occasionally build up on the coil. To get rid of this frost from the coil, the machine has to periodically enter “defrost” mode. After this procedure, which typically takes five to ten minutes, the machine will resume its regular functions. To avoid this procedure, do not try to switch the machine off and on again; it will just reset and begin the “defrost” process once more. |
| Blowing cool air when on | Because the ceiling duct is located in the surrounding air. The interior fan will release this unconditioned air through the outlets when the device is switched on. This is standard procedure and shouldn’t take longer than a minute or two. |
Air Conditioner Not Cooling
If your air conditioner is operating but it doesn’t seem to be cooling there are various symptoms.
| Problem | Treatment |
|---|---|
| Filter Blocked | Clean or replace the return air filter. |
| There a too many zones on at once | The majority of ducted systems are zoned and made to operate as many places as possible. Switch off any unused, superfluous zones. |
| There is a low refrigerant warning | Refrigerant might progressively leak over time as a result of aging or improper installation. A professional is required to fix the leak and add refrigerant, if feasible. |
| Faulty Part | There may be a fault with a part such as an electronic control board, fan motor or even the compressor. This will need to be diagnosed by a technician. |
| Hot air is blowing when the AC unit is on. | Because the ductwork is often located in a heated roof space in a standard ducted air conditioner installation. When the fan runs, the heated air is released via the outlets. This is standard procedure and should take no more than a minute or two. |
Common Troubleshooting Solutions
No Power
Check your circuit breaker in the meter box. If it’s tripped, turn it back on.
Check the isolating switch near the outdoor unit. Ensure it’s turned on.
If the circuit breaker trips frequently or the isolating switch is loose or hard to move, call an electrician.
No Airflow
Check for a faulty motor damper; this regulates airflow and may need replacement.
Inspect your ducts in the ceiling. Sometimes they can be damaged or disconnected during other work.
Leaking Water
Water dripping outside is normal during heating.
Indoor leaks often mean a blocked drain. Check the condensate drain for blockages or disconnections.
In heating mode, condensation under the outdoor unit is normal.
If water is leaking into your ceiling, the drain line may be blocked, dislodged, or broken.
Not Heating
Standby light showing? The system is warming up. Wait 5-10 minutes.
Defrost mode? Frost on the outdoor coil is melting. Wait 5-10 minutes.
Blowing cool air briefly? This can happen when starting up or during standby.
Not Cooling
Clean or replace filters.
Ensure zones are closed if not in use.
Call a professional if refrigerant levels might be low.
Hot air from vents briefly? This can happen when the ductwork is in a hot roof space.