McQuay Error Codes
Every McQuay error code we have catalogued, with what it means on site — 46 codes in total. In R-Pro, tap any code to get the meaning, likely causes and inspection steps, even with no signal in the plant room.
46 codes
| Code | What it means |
|---|---|
| U0 | Insufficient refrigerant / gas shortage |
| U2 | DC voltage out of range |
| U4 | Indoor/outdoor communication failure |
| U7 | Outdoor PCB signal transmission issue |
| UA | Installation issue / mismatched units |
| UF | Wiring or piping mismatch/damage |
| UH | Antifreeze function activated |
| A1 | Indoor main PCB defect |
| A3 | Drain water level abnormality |
| A5 | High pressure or freeze-up control |
| A6 | Indoor fan motor lock or overload |
| C4 | Indoor heat exchanger thermistor fault |
| C9 | Room temp thermistor fault |
| E1 | Outdoor main PCB defect |
| L1 | Outdoor main PCB defect |
| E3 | High pressure switch actuation |
| E4 | Low pressure switch actuation |
| E5 | Inverter compressor overload |
| E6 | Compressor lock or overcurrent |
| E7 | Outdoor DC fan motor fault |
| E8 | Input overcurrent (inverter) |
| E9 | EXV issue |
| EA | 4-way reversing valve malfunction |
| F3 | Discharge pipe overheating |
| F6 | Outdoor heat exchanger overheating |
| H0 | Compressor sensor system abnormality |
| H3 | High pressure switch defect |
| H6 | Position sensor abnormality |
| H8 | AC current sensor issue |
| H9 | Outdoor air thermistor fault |
| J1 | Pressure sensor malfunction |
| J3 | Compressor discharge pipe thermistor fault |
| J5 | Suction pipe thermistor fault |
| J6 | Outdoor heat exchanger thermistor fault |
| J7 | Subcooling heat exchanger thermistor fault |
| J8 | Liquid pipe thermistor fault |
| J9 | Gas pipe thermistor fault |
| LC | Transmission error (inverter to control PCB) |
| L3 | Electrical box temperature rise |
| L4 | Inverter heatsink overheating |
| L5 | IPM/IGBT overcurrent (compressor) |
| L8 | Compressor electrical thermal switch active |
| L9 | Stall prevention error |
| P1 | Open phase or voltage imbalance |
| P4 | Heatsink thermistor fault |
| PJ | Capacity setting error |
Official McQuay source / manual ↗
Look up any error code — offline — in R-Pro.
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