Mitsubishi Electric Error Code LED LD2
(Flash)

Full Diagnosis

Diagnosis of malfunction: this LED flash pattern indicates the outdoor unit's phase-monitoring circuit has detected a missing (open) power leg on the incoming supply feeding the compressor, distinct from LD1, which flags a reversed phase sequence where all three legs are present but wired in the wrong rotational order. It is the LED-blink equivalent used on outdoor control boards without a digital display, corresponding to the same class of fault reported as F2 (L3 open phase) or FA (L2 open phase/51CM) on units read through a digital remote or service tool. Because a missing phase leg would cause the compressor to single-phase and overheat, the outdoor board locks out compressor and often fan operation immediately and holds the lockout until incoming power is restored to all legs.

All Recorded Causes

Blown fuse or tripped breaker on one incoming phase leg. Loose, corroded, or disconnected terminal on the outdoor unit's main power block. Failed contactor with a contact not closing on one leg. Utility-side single-phasing or a downed/failed phase conductor. Damaged phase-monitoring relay or its wiring harness. Miswired or incomplete power disconnect installation.

Verify Before Replacing Parts

1. Confirm the exact Mitsubishi Electric model family and default context before acting on a generic code description.
2. Confirm filter condition, blower operation, and coil cleanliness before replacing any controls — start by ruling out whether blown fuse or tripped breaker on one incoming phase leg.
3. Measure airflow-related readings that match the symptom, such as temperature split or static pressure, and check whether loose, corroded, or disconnected terminal on the outdoor unit's main power block.
4. After the correction, run the system long enough to confirm the default fault does not return under normal load.