White countertop microwave on a kitchen counter

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Microwave door, interlock and leakage: what the federal standard requires and what to check after a door or switch repair

US microwave ovens are built to the FDA performance standard (21 CFR 1030.10): leakage may not exceed 1 mW/cm² as sold and 5 mW/cm² for the life of the oven, measured about 5 cm (2 in) from the surface, and every oven must have two independent interlocks plus a monitoring system that stops the oven if the interlocks fail. In the field that means a damaged door, hinge or seal is a stop-use condition, every interlock part goes back exactly as designed, and a door or switch repair should end with a leakage survey using a microwave survey meter. This guide covers the checks; it does not cover high-voltage work beyond the standard discharge warning.

Cross-checked ~30 min advancedBrands: All

Before you start

A microwave with a bent door, broken hinge, damaged seal or a door that does not close firmly must not be run; tag it out
Never defeat, jumper or bend an interlock or the monitor switch; the monitor switch is designed to blow the fuse if the interlocks fail
The high-voltage capacitor can hold a lethal charge after unplugging; only trained techs open the cabinet, and only after a proper discharge
Do not run the oven empty for a test; use a water load

Diagnostic steps

Unlock all 5 steps with expected values

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