Mitsubishi Electric heat-pump — Mitsubishi Electric outdoor units publishing the U-series fault table, including M-Series and MXZ multi-zone outdoor equipment Error Codes Directory

Mitsubishi U2: high discharge temperature is a charge question, not a compressor verdict

U2 is an outdoor protection stop raised when the compressor discharge temperature rises beyond the limit the control allows, a condition the reference also ties to refrigerant shortage. High discharge temperature is what a compressor does when it has too little refrigerant returning to cool it, so the code is a symptom of the refrigerant circuit rather than proof the compressor is damaged. Applies to: Mitsubishi Electric outdoor units publishing the U-series fault table, including M-Series and MXZ multi-zone outdoor equipment This applies to Mitsubishi Electric outdoor units that publish the U-series table. The same two characters appear on other manufacturers with unrelated meanings, and Mitsubishi Heavy Industries is a separate company with its own code set. Take the reading from the outdoor unit model plate, not from the brand name on the indoor grille. Owner-safe checks: Turn the system off at the controller and leave it off, since repeated restarts run the compressor under the condition that triggered the limit. | Walk the visible line set and the outdoor unit looking for oil film, frost patches, or a disturbed insulation run, and photograph anything you find. | Write down how the system had been performing over the preceding weeks and the outdoor conditions when it stopped. Qualified technician: Measuring charge, searching for a leak, recovering refrigerant, and testing the discharge thermistor are certified refrigerant-handling activities under EPA Section 608 in the United States and F-Gas rules in the United Kingdom and Europe. | Do not add refrigerant, tighten a flare, or operate the system to see whether the code stays away. Running a compressor at high discharge temperature is what the protection exists to prevent.