The Xantrex MS3000 is a 3000 W true sine‑wave inverter/charger designed for marine and industrial use, featuring a three‑stage battery charger and networking capability. Common failure points include the internal power factor correction circuitry, the AC input rectifier bridge, and the cooling fan or heat sink if operating near its 122 °F rating; the unit may also exhibit output voltage sag under high load or erratic charging behavior due to worn MOSFETs or capacitor degradation. First‑check diagnostics should verify the AC input voltage (90–135 VAC) and ensure the inverter’s internal fuses are intact, inspect the output waveform for THD compliance (<3%) with an oscilloscope, and review any diagnostic LEDs or error codes on the front panel to isolate charger stage faults.[oss-gpt-20b]