Why Capacitors go bad

Way back in my teens we had a window air conditioner in our house. It stopped working & I figured out that the run capacitor was bad. It was a big honking electrolytic. It was a hot day, so I went rummaging through electronic parts we had in the basement. We had a lot. I came up with a two section paper wound capacitor. Didn’t understand the difference between AC & DC capacitors back then. It was the same value & voltage, but alot smaller, but I thought “what the heck, let’s give it a try.”

I hooked up to the ac, hanging out the front. It started right up. I was standing in front of the ac cooling myself off, very proud of myself. About 30 seconds later it exploded violently, sending paper flying everywhere. Scared the crap out of me. I was covered with paper shreds. That’s when I learned about different types of capacitors….