Midea AC error codes – Multi-split outdoor M2/M3/M4 OC - outdoor digital tube
15 codes from the Midea service manual, with what each one means and the usual causes. Outdoor LED shows "--" standby, running frequency when running, "dF" in defrost. Press SW1 to step through check data (1 demand, 2 mode, 4 fan, 5-8 coil outlet temps, 9 condenser, 10 ambient, 11 discharge, 12 inverter current).
You can safely switch the unit off at the switch, wait 5 minutes and switch on again. Don't open the unit, touch wiring or handle gas: these checks need a trained technician.
E0
Outdoor EEPROM malfunction
Usual causes
- EEPROM chip loose (socket type)
- Outdoor main board fault
E1
Room A indoor coil outlet sensor (T2B) or its connector defective
Usual causes
- Coil outlet (T2B) sensor of that indoor room or its connector on the OUTDOOR board loose
- Sensor open/short
- Outdoor PCB
What our technician checks
- Check T2B sensor of that room and connector on outdoor PCB
- Measure resistance. Sensor table (Appendix 1, T1/T2/T2B/T3/T4): 10 kΩ at 25°C, 12.64k at 20°C, 7.97k at 30°C, 5.18k at 40°C, 35.2k at 0°C
E2
Room B indoor coil outlet sensor (T2B) or its connector defective
Usual causes
- Coil outlet (T2B) sensor of that indoor room or its connector on the OUTDOOR board loose
- Sensor open/short
- Outdoor PCB
What our technician checks
- Check T2B sensor of that room and connector on outdoor PCB
- Measure resistance. Sensor table (Appendix 1, T1/T2/T2B/T3/T4): 10 kΩ at 25°C, 12.64k at 20°C, 7.97k at 30°C, 5.18k at 40°C, 35.2k at 0°C
E3
Room C indoor coil outlet sensor (T2B) or its connector defective
Usual causes
- Coil outlet (T2B) sensor of that indoor room or its connector on the OUTDOOR board loose
- Sensor open/short
- Outdoor PCB
What our technician checks
- Check T2B sensor of that room and connector on outdoor PCB
- Measure resistance. Sensor table (Appendix 1, T1/T2/T2B/T3/T4): 10 kΩ at 25°C, 12.64k at 20°C, 7.97k at 30°C, 5.18k at 40°C, 35.2k at 0°C
E6
Room D indoor coil outlet sensor (T2B) or its connector defective
Usual causes
- Coil outlet (T2B) sensor of that indoor room or its connector on the OUTDOOR board loose
- Sensor open/short
- Outdoor PCB
What our technician checks
- Check T2B sensor of that room and connector on outdoor PCB
- Measure resistance. Sensor table (Appendix 1, T1/T2/T2B/T3/T4): 10 kΩ at 25°C, 12.64k at 20°C, 7.97k at 30°C, 5.18k at 40°C, 35.2k at 0°C
E4
Outdoor temperature sensor open/short
Usual causes
- Sensor connector loose
- Sensor open or short
- PCB input circuit fault
What our technician checks
- Check sensor-to-PCB connection
- Measure sensor resistance against table. Sensor table (Appendix 1, T1/T2/T2B/T3/T4): 10 kΩ at 25°C, 12.64k at 20°C, 7.97k at 30°C, 5.18k at 40°C, 35.2k at 0°C
E5
Compressor voltage protection
Usual causes
- Supply voltage wrong (should be about 220 V AC, unit works 190-264 V)
- Power board fault
- Bridge rectifier fault
- IPM board fault
What our technician checks
- Measure outdoor L-N: about 220 V AC
- Measure IPM board P-N: 280-400 V DC
- Rectifier: input 220-230 V AC gives about 310 V DC
E7
Communication fault between IPM board and outdoor main board
Usual causes
- IPM-to-main-board cable loose
- IPM board fault
- Outdoor main PCB fault
What our technician checks
- Check IPM board for its own error display
- Re-seat connecting cable
P0
Compressor discharge or top temperature protection (M4OC-27/36: discharge only)
Usual causes
- Gas shortage / leak
- Discharge sensor wiring wrong
- Discharge sensor faulty
- Outdoor main board fault
What our technician checks
- Is discharge temperature really above 115°C?
- Check sensor wiring to PCB
- Check for leaks
- Measure discharge sensor. Discharge sensor T5 (Appendix 2): 54.9 kΩ at 25°C, 29.2k at 40°C, 19.7k at 50°C, 5 kΩ at 90°C
P1
High pressure protection (M4OC1-27, M4OC-27, M4OC-36)
Usual causes
- HP switch wiring loose
- HP switch broken
- Very high outdoor temperature
- Poor ventilation around outdoor unit
- Dirty condenser
- Blocked refrigerant pipe
- Outdoor main board
What our technician checks
- Check HP switch wiring
- Short the HP switch socket temporarily - if unit runs, switch is bad
- Check site temperature, airflow, condenser
P2
Low pressure protection (M4OC1-27, M4OC-27, M4OC-36)
Usual causes
- LP switch wiring loose
- LP switch broken
- Outdoor temperature too low
- Refrigerant leak (pressure below 0.14 MPa)
- Blocked pipe
- Outdoor main board
What our technician checks
- Check LP switch wiring
- Short the LP switch socket temporarily - if unit runs, switch is bad
- Gauge on service port: below 0.14 MPa = leak
P3
Compressor current protection
Usual causes
- Input current too high (limits: 8.5 A small units, 15 A for 18-21K and 27K 1x3, 18.5 A 27K 1x4, 21.5 A 36K)
- High outdoor temperature
- Poor ventilation
- Dirty condenser
- Blocked pipe
- Outdoor main board
What our technician checks
- Clamp the supply current
- Check refrigerant system, site temperature, airflow, condenser
P4
IPM module protection
Usual causes
- IPM P-N voltage wrong (needs 277-356 V DC for 14-27K, 277-410 V DC for 36K)
- Supply not 220-240 V
- Loose cable main board-IPM
- Compressor leads loose / wrong
- Bridge rectifier shorted
- Reactor wire broken (∞ Ω) or PFC module faulty (M5OA-36)
- IPM module, main board or compressor faulty
What our technician checks
- Measure P-N on IPM
- Check supply voltage and wiring
- Check cable main board-IPM and compressor connections
- Measure bridge rectifier: no terminal pair should read 0 Ω
- Measure reactor: open (∞) = broken
- Compressor phase-phase U-V, U-W, V-W 60-150 V AC when running
P6
Condenser high temperature protection
Usual causes
- Condenser temperature above 65°C (stops
- restarts below 52°C)
- High outdoor temperature
- Dirty condenser
- Blocked pipe
- Condenser sensor wrong
- Outdoor main board
What our technician checks
- Measure condenser temperature
- Check T3 sensor resistance. Sensor table (Appendix 1, T1/T2/T2B/T3/T4): 10 kΩ at 25°C, 12.64k at 20°C, 7.97k at 30°C, 5.18k at 40°C, 35.2k at 0°C
P7
Inverter compressor drive protection
Usual causes
- Same as IPM protection: supply, P-N voltage, IPM, compressor, reactor
What our technician checks
- Follow IPM module protection checks
Code not here, or still showing?
Send a photo of the display and the model sticker on WhatsApp. We'll tell you what it means and whether it needs a visit.
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