Mitsubishi U6: the inverter cut the compressor current before anything melted

What Does Error U6 Mean?

U6 is raised when the outdoor inverter detects compressor current or power module conditions outside the range it will drive. It is an electrical protection acting in milliseconds, which is why the code arrives as an abrupt stop rather than a gradual loss of output. The detection names the current, not the cause of the current. Applies to: Mitsubishi Electric inverter outdoor units publishing the U-series fault table, including M-Series single-zone and MXZ multi-zone equipment The entry described here belongs to Mitsubishi Electric outdoor units publishing the U-series table. Multi-zone outdoor units serving several indoor heads report the code centrally, so the address shown does not identify a room. Confirm the outdoor model from its plate before applying this reading. Owner-safe checks: Attempt at most one restart from the controller, then stop and note how long the outdoor unit ran before the code returned. | Check whether other appliances on the property are behaving normally and whether any protective device in the consumer unit or panel has operated. | Leave the isolator on and the operation off for several hours before any further attempt if the system has been unused for a long period. Qualified technician: Measuring compressor winding resistance, drive output, and supply voltage under load requires opening an energised outdoor enclosure and is qualified work. | A burning smell, visible scorching, or a protective device that trips when the unit starts is a stop condition. Isolate at the dedicated switch and arrange service without further attempts.