Over-the-range microwave mounted above a stainless electric range
Generic photo: Curtis Adams · Pexels License

Replace the over-the-range microwave door interlock switches (discharge the HV capacitor first)

Microwaves have two or three interlock switches (primary, secondary and a monitor) at the door latch. They are high-safety parts: the monitor switch deliberately blows the line fuse if the others fail closed. On over-the-range units access is usually by removing the control panel or vent grille and the latch/switch bracket. Unplug, discharge the high-voltage capacitor, replace all the switches with the exact types for each position, replace the fuse, and test.

Single source ~60 min advancedBrands: All

Before you start

  • Unplug the microwave before removing any panel. The high-voltage capacitor can hold a lethal charge after the unit is unplugged: discharge it with an insulated resistor tool before touching anything inside.
  • Never operate the microwave with the outer case, grille or control panel removed, or with a switch bypassed.
  • Replace each switch with the exact part for its position; normally-open and normally-closed switches are not interchangeable.
  • If you are not trained for microwave high-voltage work, refer the job.

Diagnostic steps

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Replace the over-the-range microwave door interlock switches (discharge the HV capacitor first) · OnCall Tech