The wires connecting to the normally closed switch have a short circuit across them, which is causing the switch to stay closed all the time! The clock works, but when you try to cook something the fuse blows. What could be causing the short?

  • what switch are you talking about?
    – jsotola
    Dec 5 '19 at 7:11
  • 2
    Please consider re-wording this question to provide additional information such as the make and model of the microwave unit, which microswitch you are talking about, and what fuse you are talking about. What you have written here makes no sense at all and it's impossible for someone to assist you based on it.
    – jwh20
    Dec 5 '19 at 10:34

Typical microwave ovens will have multiple micro switches that are designed to provide safe use of the unit. Safe use translates to making sure the door is closed before the unit is able to produce the microwave energy.

The safety feature is normally designed so that the multiple switches have to sequence on/off properly when the when the microwave door is opened and closed. If the switch sequencing fails (broken mechanism, misaligned switches or user attempted defeat of safety feature) the wiring is designed to place a short across the AC power line in the microwave downwind from the fuse. The result is that the fuse blows and prevents operation of the oven in the unsafe mode.

In your case the problem is likely to be one of the other switches has failed or the interlock mechanism that triggers these switches is broken or misaligned.

You may want to reference this older question and additional links therein:

Microwave door interlock switch keeps failing

Pay particular attention to comments regarding OEM replacement switch costs versus buying switches from an electronics supplier.

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