Microwave trips the household circuit breaker or blows fuse when starting a cook cycle

Safety: Repeated breaker tripping indicates a potentially dangerous short. Avoid repeated reset attempts.

• Isolate the issue: Confirm that the breaker trips only when the microwave attempts to heat (not when just plugging in or using the light/fan).
• Visual inspection: With power disconnected, remove the cabinet and inspect for burnt wiring, melted insulation, or arcing marks near the transformer, capacitor, and line filter board.
• Do not touch HV parts: Do not attempt to disconnect or test the high-voltage capacitor or transformer unless trained.
• Professional repair: A technician should test the high-voltage capacitor, transformer, and line filter for shorts and replace the defective component.