Mitsubishi Electric UF

What does Mitsubishi Electric UF mean?

The control interrupted the compressor on overcurrent because the compressor appears locked, and shows UF on a blinking display. When the compressor motor cannot turn, current spikes, so the inverter shuts it down to prevent damage. A locked compressor can be caused by a mechanical seizure, an electrical fault, or a refrigerant-side condition that stalls startup.

Symptoms

• UF shown on a blinking display
• Compressor attempts to start then stops immediately
• Humming or buzzing without the compressor running
• No cooling or heating output

Common causes

• Mechanically seized or locked compressor
• Compressor motor winding fault
• Abnormal supply voltage at startup
• Refrigerant migration causing a hard start
• Inverter or power-module fault

Diagnostic steps

1. 01

   Power down fully

   Switch off the outdoor unit and wait before any restart.

2. 02

   Check the power supply

   Confirm the outdoor unit receives correct, stable voltage on its terminals.

3. 03

   Attempt one reset

   Restore power once and observe whether the compressor starts or UF returns at once.

4. 04

   Listen at startup

   Note whether the compressor hums without turning, which suggests a lock.

5. 05

   Stop repeated restarts

   If UF persists, leave the unit off and arrange service to avoid further damage.

When to call a professional

UF points to a locked compressor and overcurrent trip, which a licensed technician must diagnose. Testing the compressor windings, the inverter, and the supply involves high-voltage work, and a seized compressor may require refrigerant recovery to replace. Repeated reset attempts can cause more damage, so have a qualified professional investigate before further operation.