When I got home today, Becki showed me that the microwave was not working. The timer would count, but it would not heat anything. After a quick Google search, I found a video that suggested the problem could be one of the door sensors. The video went on to show how to test the sensors with a volt meter. I do not have volt meter, but I do have electromagnets. The kids and I made them a while ago and then used them as demos when I taught the first Science By Immersion class.
There were 3 switches in the microwave that I needed to test (although I only saw 2 at first). I did not have the “right” equipment to test the switches, but I basically just needed to see if electricity would flow through them when the button was down and stop when the button was up.
The first thing that I noticed when I took the panel of off the microwave was a tight coil of wires. Do you know what it is?
The copper colored wire in the middle of the picture is an electromagnet! This one is much stronger than the ones that we made. At that point I was kind of hoping that I could not fix the microwave, because I wanted to take out that great electromagnet.
I laid out all of the pieces that I needed to test the switches (minus the 3rd switch that I did not see).
I connected one of the electromagnet wires to a lead on the switch and the other one to the battery. Then I held the other lead on the switch to the battery and tested to see if it would pick up the paperclip. It did not. Broken switch? No, I just forgot to push the button. Now it works.
So that switch was good. When I tested the next one, it picked up the paperclip before I pushed the button and dropped it when I did push it. Was it broken? Well I took them both apart to see what was happening.
As you can see, they are slightly different designs. One is supposed to close the circuit when the button is pushed and the other is designed to close the circuit when the button is not pushed in. So both switches were working correctly.
Here are some close ups so you can see how the switch works. (The curved piece is a spring that returns the button to its normal position.)
When I found the 3rd switch, I thought it might be the problem, because it looked a little melted.
I tested it and it did not work.
So I disassembled it and tried to fix it. The contact points inside the switch were covered with a thin black residue.
So I rubbed some sand paper on them to make them nice and shiny. I also bent the metal plate slightly to ensure that the contacts would reach each other.
Then I put everything back together, and the microwave is working again!
I showed the kids all of the steps as I did them. They were excited to see the electromagnet in the microwave, and thought it was fun that I was using the electromagnets that we made. Elijah is very interested in electricity, so he enjoyed seeing the inside of the switches.
Isaiah exclaimed, “I can’t believe it. You fixed the microwave with science!”
When something is broken, you might as well take it apart before you buy a new one. You might be able to fix it, and you might learn something.