Mijia Air Conditioner Pro Eco LABEL EGAT NO.5 (3 Star) 12000BTU Inverter FAQ

Serial Number

Error Code Category

New Error Code

Error Definition

Error explanation

Solution

1

Sensor Fault Protection

F1.1

Indoor ambient temperature sensor failure

Indoor unit ambient temperature sensing pack failure

1. Find the corresponding sensor according to the displayed error code, re-plug the sensor, and confirm whether the sensor failure is caused by poor contact;
2. Use a multimeter to test the sensor resistance to detect whether there is a short circuit, open circuit, or whether the resistance value. Hold the temperature sensor with your hand and detect its resistance. If it gradually decreases, it is normal. If there is a fault, replace the corresponding sensor;
3. You can use the "debugging mode" to see whether the corresponding displayed temperature is normal for auxiliary judgment. If it displays "50" or "0" or "--" and flashes, it means that the sensor is abnormal.

2

F1.2

Outdoor ambient temperature sensor failure

Outdoor unit ambient temperature sensing pack failure

3

F2.1

Indoor coil temperature sensor failure

Indoor unit pipe temperature sensing pack failure

4

F2.2

Outdoor coil temperature sensor failure

Outdoor unit pipe temperature sensing pack failure

5

F2.3

Indoor pipe temperature sensing pack failure

Indoor unit pipe temperature sensing pack failure protection

6

F2.4

Outdoor pipe temperature sensing pack failure protection

Outdoor unit pipe temperature sensing pack failure protection

7

F3.1

Outdoor exhaust temperature sensor failure

Outdoor unit exhaust temperature sensing pack failure

8

F3.2

Exhaust temperature sensing pack failure protection

Outdoor unit exhaust temperature sensing pack failure protection

9

Electronic Control Hardware Error

E1

Outdoor EEPROM failure

Outdoor unit electronic control program failure

1. If you use an after-sales board, check whether the EEPROM parameters match;
2. Replace the outdoor unit electronic control board.

10

E3

Communication failure between the indoor unit board and the display board

Communication failure between the indoor unit board and the display board

1. Check the connection wires between the main board and the display board to ensure that the wire sequence and connection are reliable: replug and connect;
2. If the wires are normal, replace the indoor unit board or display board.

11

E6.1

Indoor and outdoor communication: Data cannot be received indoors

Communication failure between the indoor and outdoor units main boards

1. Eliminate communication failures caused by poor power supply and wiring;
2. Check unit connections;
3. Test and determine the voltage of the indoor unit;
4. Check the outdoor unit.

12

E6.2

Indoor and outdoor communication: Data cannot be received outdoors

Communication failure between the indoor and outdoor units main boards

13

E8.1

Communication failure between the outdoor unit compressor chip and the fan chip

Outdoor unit electronic control communication failure

Replace the outdoor unit electrical control panel.

14

E8.2

Communication failure between indoor unit board and fan chip

Indoor unit electronic control communication failure

Replace the indoor unit electrical control panel.

15

FF

The indoor unit cannot receive the Internet module (SOC, Wi-Fi) communication failure

Indoor unit display panel communication failure

Request and replace the display board.

16

Fan Error

E0

Indoor PG/DC fan failure

Indoor unit fan failure

1. Move the fan to confirm whether it is stuck. If the fan blade is stuck, remove it and reassemble it;
2. Check the circuit between the circuit board and the motor line. If the terminal is out of place, oxidized, or disconnected, reconnect it and ensure the connection is reliable;
3. Detect the resistance between the motor terminals. If it is abnormal, replace the motor;
Note: When replacing the motor, connect the new motor to the main board and test it. If it works normally, replace it. If it is abnormal, continue to check the main board.
4. If there is no problem with the above inspection, check the output voltage of the main board to confirm whether it is a main board problem. If there is a problem, replace it.

17

E2 (E2.1/E2.2/E2.3/E2.4/E2.5/E2.6/E2.7)

Outdoor DC fan failure

Outdoor unit fan failure

1. Move the fan to see if it is stuck. If so, reassemble or replace the deformed parts;
2. Check the circuit between the circuit board and the motor line. If the terminal is out of place, contact is poor, or circuit is disconnected, reconnect it reliably;
3. Detect the resistance between the motor terminals. If it is abnormal, replace the motor.
Note: Before replacing the motor, connect the new motor to the main board for testing. If the new motor runs normally, replace it. If it runs abnormally, check whether it is a main board problem.

18

Outdoor Unit Electronic Control Drive Protection

U0

U0.0: Inverter DC over-voltage fault
U0.1: Inverter DC low voltage fault
U0.2:Inverter DC voltage mutation fault
U0.3:AC input low voltage (effective value) detection fault

Outdoor unit electronic control voltage failure

1. First check whether the input voltage at both ends of the N and L lines on the white wiring terminal of the outdoor unit is within the normal allowable range (160V, 260V) and test it in the power-on state. If it exceeds this range, it is normal protection;
2. Check whether the grid voltage fluctuates greatly and has mutations, and restart the machine after a period of time;
3. If the voltage is normal, there is a problem with the voltage sampling circuit, and replace the outdoor electric control board.
Note:
Before replacing the outdoor main board, test whether the compressor is short-circuited to the copper pipe and whether the three-phase resistance is consistent.

19

U1.1

Inverter module fault/inverter module hardware over-current fault

Outdoor unit electric control module current fault

1. Check the compressor wiring, if the wiring is bad, rewire
2. Unplug the UVW line at the compressor end and re-power on. If the fault cannot be cleared, replace the outdoor unit electronic control;
3. If the impedance between the compressor phase line and the casing is too low, replace the compressor;
4. If the electronic control board is a common spare part, it could be that the electronic control and compressor parameters do not match, and the E-side program needs to be refreshed;
5. Replace the outdoor unit electronic control board;
6. Check whether the system condensing pressure is too high: abnormal fan (replace the motor), too much refrigerant (refill), capillary blockage (replace the capillary), dirty blockage inside the two devices (replace the two devices);
7. Replace the compressor.

20

U1.2

Outdoor current sensor failure

Outdoor unit electric control current fault

21

U1.3

Compressor phase current circuit detection fault

Outdoor unit compressor current fault

22

U2(U2.1/U2.2/U2.3)

Over-current protection

Outdoor unit electric control over-current protection

1. Check if the voltage is too low;
2. Check if the outdoor unit heat exchanger is dirty or blocked; the outdoor unit does not exchange heat well in the grille
3. Check if the indoor/outdoor unit air outlet is not smooth;
4. Check if the indoor unit filter is dirty or blocked;
5. Check if the indoor/outdoor motor speed drops;
6. Check if the indoor/outdoor fan blades are damaged;
7. Check if the refrigerant is abnormal: After eliminating the actual current over-current protection, if the actual current is lower than the rated current and the protection is still on, the current detection circuit can be faulty, causing the detected current to be greater than the actual current value. Replace the outdoor unit electric control board.
In addition, if the protection code appears under high temperature and other conditions, the machine can operate properly, which is normal. The protection will be eliminated when the temperature drops.

23

U3

Drive initialization fault

Outdoor unit drive start failure

1. Check whether the main power supply voltages of the outdoor unit (DC310V, DC15V, DC12V, DC5V) are normal;
2. Replace the outdoor unit control board (if the abnormal voltage is caused by the electronic expansion valve coil or the DC fan, replace the electronic expansion valve coil or the DC fan).

24

U4（U4.1/U4.2/U4.3/U4.4）

Step loss detection/Compressor step loss protection

Outdoor unit compressor out-of-step protection

1. System pressure imbalance, insufficient shutdown time-wait for 3-5 minutes before restarting;
2. Abnormal input voltage-use a voltage stabilizer;
3. Check whether the compressor wiring is properly connected and in the correct sequence-reconnect if necessary;
4. Faulty external fan motor-replace the motor;
5. Poor heat dissipation-clean the heat exchangers and improve the heat dissipation environment;
6. Control board phase sampling resistor value deviation or sampling circuit failure-replace the control board;
7. Excess refrigerant-recharge according to the required specifications;
8. Compressor failure (such as seizure, winding short circuit, or open circuit)-replace the compressor.

25

U5

Compressor phase loss/Reverse phase protection

Outdoor unit compressor missing/reverse phase protection

26

U6.1

Module temperature protection

Outdoor unit electronic control module temperature protection

1. Check the voltage; it should be between 170V and 270V—use a voltage stabilizer;
2. Check if the outdoor unit heat exchanger is dirty or blocked—remove obstructions or clean the condenser;
3. Ensure smooth airflow from the outdoor unit-remove any obstructions;
4. Check if the outdoor unit motor speed has decreased or if the fan blades are damaged-replace the motor or fan blades if needed;
5. If the module temperature detection circuit is faulty-replace the outdoor unit control board.

27

U6.2

Module temperature sensor circuit fault

The temperature sensing pack of the outdoor unit electronic control module is faulty

1. Check if the module board is making proper contact with the heat sink. Ensure tight, debris-free, and seamless contact between the module and the heat sink. Secure the module board screws properly. If needed, replace the outdoor unit control board;
2. Abnormal outdoor system or excessive compressor current—refer to U6.1;
3. Module temperature detection circuit failure—replace the outdoor unit control board.

28

U8.1

PFC hardware over-current

Outdoor unit electronic control PFC circuit over-current protection

1. System pressure imbalance, insufficient shutdown time—wait for 3–5 minutes before restarting
2. Abnormal input voltage—use a voltage stabilizer;
3. Check if the compressor wiring is properly connected and in the correct sequence—reconnect if necessary;
4. Faulty outdoor fan motor-replace the motor;
5. Poor heat dissipation-clean the heat exchangers and improve the heat dissipation environment;
6. Control board phase sampling resistor deviation or sampling circuit failure-replace the control board;
7. Excess refrigerant-recharge according to the required specifications;
8. Compressor failure (such as seizure, winding short circuit, or open circuit)-replace the compressor.

29

U8.2

PFC software over-current

Outdoor unit electronic control PFC circuit over-current protection

1. Sudden fluctuation in mains voltage—normal protection; use a voltage stabilizer;
2. Inductor (reactor) short circuit or PFC detection circuit failure-replace the outdoor unit control board.

30

U8.3

PFC RMS over-current protection

Outdoor unit electronic control PFC circuit over-current protection

1. System pressure imbalance, insufficient shutdown time-wait for 3–5 minutes before restarting;
2. Abnormal input voltage—use a voltage stabilizer;
3. Check if the compressor wiring is properly connected and in the correct sequence-reconnect if necessary;
4. Faulty outdoor fan motor-replace the motor;
5. Poor heat dissipation-clean the heat exchangers and improve the heat dissipation environment;
6. Control board phase sampling resistor deviation or sampling circuit failure-replace the control board;
7. Excess refrigerant-recharge according to the required specifications;
8. Compressor failure (such as seizure, winding short circuit, or open circuit)-replace the compressor.

31

Drive Limit Frequency Reduction (display 17)

C1

Module current (compressor phase current) protection limit/frequency reduction

Outdoor unit electric control module current limit/frequency reduction

1. Check if the voltage is too low; use a voltage stabilizer;
2. Check if the outdoor unit's heat exchanger is dirty or clogged; if the outdoor unit has poor heat dissipation due to being inside a grille: clean both heat exchangers and improve the heat dissipation environment;
3. Check if the airflow of the indoor/outdoor unit is obstructed; improve the heat dissipation environment;
4. Check if the indoor unit's filter is dirty or clogged; clean the filter and improve the heat dissipation environment;
5. Check if the rotation speed of the indoor/outdoor motor has decreased; replace the motor;
6. Check if the indoor/outdoor fan blades are damaged; replace the indoor and outdoor fans.
After excluding the actual current over-large protection, for example, if the actual current is lower than the rated current but the protection is still on, it may be due to a fault in the current detection circuit, causing the detected current to be greater than the actual current value. Replace the outdoor unit electronic control board.

32

C2

External AC current protection limit/frequency reduction

Outdoor unit electric control AC current limit/frequency reduction

33

C3

Compressor module temperature limit frequency reduction

Outdoor unit electric control module temperature limit/frequency reduction

34

C4

Whole machine current peak limit frequency reduction

Outdoor unit electric control current peak limit/frequency reduction

35

C5

Drive protection limit/frequency reduction

Outdoor unit electric control drive protection limit/frequency reduction

36

System Protection

P1

Outdoor unit exhaust temperature over-high protection

Outdoor unit exhaust temperature over-high protection

1. Check if the outdoor unit is operating under extreme high-temperature conditions. This protection is for the safety of the air conditioner;
2. Check if the outdoor unit is improperly installed, such as having obstructions at the air outlet, intense sun exposure, or poor ventilation. If so, adjust the installation position;
3. Check if the outdoor unit condenser or the indoor unit filter is dirty or blocked. If so, clean them promptly;
4. Check if the indoor and outdoor fans are not operating or running too slowly;
5. Check if the motor power supply circuit on the control board is normal, and if the motor capacitor is functioning properly. If not, replace the motor;
6. Check if the refrigeration system is clogged, and if the capillary tube is frosted and not melting. If so, replace the capillary tube or other clogged components;
7. Check if the system's operating pressure is normal (Connect a pressure gauge to measure the low-pressure side operating pressure. Normal cooling system pressure range is approximately 0.8-1.3MPa, and the normal heating system pressure range is approximately 2.0-3.6MPa) to determine if there is refrigerant leakage or air intake. If so, refill with the appropriate amount of R32 refrigerant;
8. Confirm if the exhaust temperature sensor is sensing the temperature correctly (resistance is normal). If the actual pipe temperature is low, and the detected temperature exceeds 100°C (for example, after 30 minutes of shutdown, there is a significant difference between 15 and 14), compare the sensor's resistance with the resistance table. If the resistance is abnormal, replace the sensor;
9. If all the above checks are normal, replace the outdoor unit control board.

37

P2

Limit/Reduction frequency (display 17)

38

P2.1

Exhaust protection limit/reduction frequency

Outdoor unit exhaust temperature over-high limit/reduction frequency

P2.1 Check according to P1

39

P2.2

Anti-freezing protection limit/reduction frequency

Refrigerant anti-freezing limit/reduction frequency

P2.2 Check according to P5

40

P2.3

Anti-condensation protection limit/reduction frequency

Indoor unit evaporator anti-condensation limit/reduction frequency

P2.3 Anti-condensation protection: When humidity is too high and the device is operating at low speed, reduce the frequency to prevent excessive condensation. This is a normal protection. Close windows and doors or adjust the fan speed to high.

41

P2.4

Power over-high limit/reduction frequency

Overall unit power over-high limit/reduction frequency

P2.4 Check according to U2

42

P2.5

Overload protection limit/reduction frequency

Overall unit overload limit/reduction frequency

P2.5 Heating overheat protection: Same as P4 or P6

43

P5

Over-cooling protection in cooling mode

Evaporator over-cooling protection in cooling mode

1. Check if the indoor unit filter is clogged. If so, clean it;
2. Check if the indoor unit's air intake is blocked by foreign objects (curtains, paper, etc.). If so, remove the objects blocking the air intake;
3. Check if the indoor unit's cross-flow fan is stuck. If so, replace the bearings or fan, and tighten the fan screws;
4. Check if the indoor fan is not running or running too slowly;
5. Check if the motor power supply circuit on the control board is normal and whether the motor capacitor is functioning properly. If not, replace the motor;
6. The internal coil temperature sensor's IPT resistance can drift, causing the temperature sampled by the chip to deviate from the actual temperature. Replace the internal coil temperature sensor. Use the remote control to check the device's detected internal coil temperature with code 12. If the reading is significantly low (it shouldn't normally be lower than 5°C), replace the internal coil sensor. If the fault cannot be cleared, replace the indoor control board;
7. Check if the system's operating pressure is normal (Connect a pressure gauge to check the low-pressure side's operating pressure. The normal cooling system pressure range is about 0.8~1.3MPa). If there is refrigerant leakage, refill with the required amount of R32 refrigerant;
8. If all the above are normal, it can be an issue with indoor and outdoor communication data, and the indoor control board needs to be replaced.

44

P8

Outdoor unit high/low temperature protection

Outdoor unit high/low temperature protection

1. Check if the outdoor ambient temperature is normal for cooling operation. If the ambient temperature is abnormal, it is normal protection. This occurs when the cooling temperature exceeds the protection range (low-temperature cooling is more likely to occur);
2. Observe if the outdoor unit is located in a confined or narrow space where heat dissipation is poor, causing the outdoor environment temperature to be too high or too low. If heat dissipation is confirmed to be poor, move the outdoor unit to ensure proper ventilation and heat dissipation;
3. If this code appears when the ambient temperature of the overall unit is within the normal range, it indicates that the outdoor ambient temperature sensor is faulty, resulting in inaccurate temperature sampling. First, replace the outdoor ambient temperature sensor. If replacing the sensor does not clear the fault, replace the outdoor power board.

45

PA

Refrigerant shortage protection/abnormal refrigerant circulation protection

Overall unit refrigerant shortage protection/abnormal refrigerant circulation protection