In the townhouse on Cornell, The customer had me install a fixture that was very pretty, and I wish I would have taken a picture of that to post here as well. I have to try to strive to be not only mechanical but artistic, decorative and aesthetically pleasing in my posts. A shot of that lovely "bird's nest" fixture would have been a a nice compliment to the cutaway (break away) view of these switches.
At any rate, after the fixture was done, she showed me two switches that were not controlling their respective lights. They were soft and spongy to the touch. They very easily slide up and down from "on" to "off" without giving that crisp, "snapping into place" feeling. To me, that is a sure sign that the switches themselves are broken internally. Upon removal of the trim plate, it was obvious that was the case. In essence, these switches are just little "gate-keepers" for the electricity. They are plastic housings that contain 2 metal screws, called terminals, on the outside. To one of those terminals you attach the wire from the circuit breaker panel that is "hot" (has live electricity as long as breaker is on) and to the other terminal you attach the "switch leg." (the wire that will carry the electricity to the light fixture when you flip the switch to the on position.) By code, the hot wire should be black or red, and the switch leg wire should be blue, yellow, brown or orange. I say SHOULD BE with a grain of salt because in reality I have seen every color wire available used for both sides of the switch. (There is an old saying among electricians..."the electricity don't care what color the wire is!" ) Sadly, guys will often use whatever color they have left over on the truck, hence all the calls I get from bewildered DIYers who say they followed the instructions in the book exactly but it keeps sparking and tripping the breaker when they turn it on.
But essentially, the switch just has a small piece of metal inside, and internally it connects those two brass terminals so that the electricity can pass through and flow to the load (fixture) when the switch is turned on. It has a small spring inside that helps snap the toggle handle into place when you move it up and down, on and off. But these things don't last forever, and eventually the plastic components or housing can develop cracks a and break for repeated mechanical stress over the years. The plastic housing can start to come apart, and that spring inside can fall out of place, rendering it "mushy and listless" to the touch. By that time, the metallic connections inside can se shot as well, and moving the switch up and down may have no effect on the light. Often, but not always, the switch will make a popping, sizzling sound, blacken, or overheat, as the no longer aligned internal metallic contacts arc by making poor contact. Eventually, The switch will reach a point where it is severely broken down, being held in place by inertia, by the wires that are attaching to it, and by the mounting screws. When you remove the decorative trim plate, and then back out the mounting screws to remove the switch, it will literally fall apart before your very eyes. (second from top picture) I have included a picture of the replacement switch I installed (bottom before taping, second to bottom after taping), a picture of the completely disintegrated switch, and at the top, an array of various switch parts that were left over when I replaced the switch.
Remember, if your switches feel soft or mushy, or you hear a fizzing or cracking sound coming from them, call your licensed Electrician ASAP!