Mitsubishi Error Code U4: Outdoor Thermistor Short/Open
Warning: Your Mitsubishi HVAC system has detected an issue with the outdoor thermistor, which may affect its performance and efficiency.
How to Fix Mitsubishi Code U4
- Check for any visible damage or debris around the outdoor unit and remove if present
- Ensure that the outdoor unit is properly grounded and that all electrical connections are secure
- If the issue persists, contact a professional HVAC technician for further diagnosis and repair
How to Reset Mitsubishi Code U4
- 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.
What does U4 mean?
The U4 error code on your Mitsubishi HVAC system indicates a short or open circuit in the outdoor thermistor. The thermistor is a temperature-sensing component that plays a crucial role in maintaining your system's optimal performance. When it malfunctions, your HVAC system may not accurately sense the outdoor temperature, leading to incorrect operation and potential comfort issues.
Affected Models
Replacement Parts
| Part | OEM Number | Est. Cost |
|---|---|---|
| Outdoor Thermistor | 5401A000000 | — |
Related Codes on Same Models
| Code | Description | Severity |
|---|---|---|
| 1 | Indoor/Outdoor Mismatch | Warning |
| 2 | Power Supply Phase Error | Warning |
| 3 | Communication Error | Warning |
| 4 | Inverter Error | Warning |
| 5 | Outdoor Thermistor Open/Short | Warning |
| 6 | Indoor Freeze/Overheat | Warning |
| 7 | Outdoor Freeze/Overheat | Warning |
| E6 | Indoor/Outdoor Communication Error | Warning |
| E9 | Indoor/Outdoor Communication Fault | Warning |
| P1 | Intake Sensor Error | Warning |