Microwave Starts When Door is Opened

The microwave in my workplace started acting weird. It would start automatically when you open the door. Googling it revealed that this is a common issue that is caused by a malfunctioning door switch.

Alright, it was time to take it apart.

WARNING! Make sure to unplug the unit and then discharge the internal capacitor to avoid electrocuting yourself.

The high voltage capacitor is the one on the bottom right with red wires going out of it. To discharge hold a screwdriver to its left terminal and ground. If you look carefully, there’s anyway a resistor shunt that does this automatically but better to be safe than sorry.

Did you see? This was a GE microwave but all the main components are Samsung!

If you need a video on how to do this see https://youtu.be/OEet8SKsRc4?t=3m36s for more info.

Now, back to finding the malfunctioning switch. Let’s look behind the door panel.

Door switches are circled in green

There are three switches detecting the state of the door. I didn’t research what each of them were supposed to do but it was clear that one of them had lost its springy properties.

So, one of the normally open switches would close even when the door is open causing the microwave to start automatically. Below, is the faulty switch and on the right you can see its springy part (circled in red) is worn out.

I was able to fix it by bending this tiny pice of metal but overtime it would fail again, so I ended up purchasing a replacement switch from Amazon (https://www.amazon.com/gp/product/B074DYY29L/).

It was an easy fix, which saved what would otherwise have been a broken and scary microwave!