Midea AC error codes – Multi-split outdoor M5OA-36HRDN1-Q
17 codes from the Midea service manual, with what each one means and the usual causes. This model uses its own outdoor code list.
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
E2
Indoor / outdoor communication error
Usual causes
- Wrong / loose wiring between indoor and outdoor terminals
- Signal line S fault
- IPM or PFC board not powered (multi outdoor)
- Reactor disconnected
- Wrong number of indoor units detected
- Indoor or outdoor PCB fault
What our technician checks
- Power off at breaker, power on again
- Check wiring follows the wiring diagram
- Measure Vs (voltage between S and L2/N): it should swing between positive and negative
- With all indoors off, check IPM power LED on and PFC LED (qua-zone)
- Outdoor check button: press 18 times to see how many indoor units are detected (2 dual, 3 tri, 4 quad)
E3
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
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
E6
PFC module protection
Usual causes
- Loose cable main board-PFC
- PFC inductance (reactor) faulty
- PFC module faulty
What our technician checks
- Check cable
- IPM P-N voltage should be 380-390 V DC with PFC working
- Check PFC inductance
F1
Room A coil outlet sensor 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
F2
Room B coil outlet sensor 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
F3
Room C coil outlet sensor 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
F4
Room D coil outlet sensor 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
F5
Room E coil outlet sensor 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
P1
High pressure protection
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
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
Compressor discharge temperature protection
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
P5
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
P6
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
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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