Heart Interface 34‑5005‑01 AC Monitor is an industrial power‑monitoring module that measures line voltage, current and power for use in battery‑inverter systems. Common failures on this model include a burned‑out shunt resistor, damaged MOSFETs in the DC‑to‑AC conversion stage, or a cracked PCB due to vibration; symptoms often appear as erratic or no display, flashing error LEDs, or sudden loss of power output. First‑check diagnostics: verify that the input AC supply is within spec and that all connectors are secure; inspect the board for visible burn marks or loose solder joints; read any fault codes from the module’s diagnostic port or LED status indicators before proceeding to component replacement.[oss-gpt-20b]