Mitsubishi Error Code U1: High Pressure Trip
Warning: Your Mitsubishi HVAC system has experienced a high pressure trip. It's safe to operate, but you should schedule a professional repair soon.
LED Blink Pattern
How to Fix Mitsubishi Code U1
- Check and replace your air filter if it's dirty.
- Turn off your HVAC system and wait for the pressure to equalize (about 24 hours).
- If the system still doesn't work, call a professional HVAC technician.
How to Reset Mitsubishi Code U1
- Turn off the unit using the remote control or wall controller.
- Turn off the circuit breaker for the outdoor and indoor units. Wait 60 seconds.
- Restore power at the breaker.
- Turn the unit on with the remote control. If the error returns, the fault needs professional diagnosis.
Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.
What Does Mitsubishi Error Code U1 Mean?
The U1 error code on your Mitsubishi HVAC system indicates that the high pressure switch has been activated, causing the system to shut down. This is a safety feature designed to prevent damage to the compressor. The most common causes of this error are a refrigerant leak, a faulty expansion valve, or a clogged air filter.
Common Causes
- Refrigerant leak
- Faulty expansion valve
- Clogged air filter
- Dirty evaporator coil
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| You notice ice buildup on the outdoor unit | The refrigerant level | Normal (not low) |
| The system doesn't cool properly | The air filter | Clean |
Applicable Mitsubishi Models
- City Multi (VRF)(electric)
- City Multi (Y)(electric)
- Diamond (PJ)(electric)
- Diamond Plus(electric)
- Diamond Series(electric)
- Ducted Systems(electric)
- M-Series(electric)
- MSZ(electric)
- MSZ Series(electric)
- MSZ-AP(electric)
- MSZ-AP Series(electric)
- MSZ-AP5 Series(electric)
- MSZ-AS(electric)
- MSZ-FD(electric)
- MSZ-FE(electric)
- MSZ-FS(electric)
- MSZ-FS/FD Series(electric)
- MSZ-FT(electric)
- MSZ-FY(electric)
- MSZ-GE(electric)
- MSZ-LV(electric)
- MUZ-FE Series(electric)
- P-Series(electric)
- PUMA(electric)
- PUMY(electric)
- Puff (P-Series)(electric)
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| High pressure switch | 510140-0000 | — | Find Part |
| Expansion valve | 510180-0000 | — | Find Part |
| Refrigerant | — | — | — |
Related Codes on Same Models
Other codes that affect the same Mitsubishi model families as U1.
| Code | Description | Severity |
|---|---|---|
| 1 | Indoor/Outdoor Mismatch | Warning |
| 2 | Power Supply Phase Error | Warning |
| 4 | Inverter Error | Warning |
| 7 | Outdoor Freeze/Overheat | Warning |
| E6 | Indoor/Outdoor Communication Error | Warning |
| E9 | Indoor/Outdoor Communication Fault | Warning |
| P2 | Indoor Pipe Thermistor Error | Warning |
| P4 | Drain Sensor Error | Warning |
| P6 | Coil Freeze/Overheat Protection | Warning |
| U2 | Low Voltage/Overcurrent | Warning |