My rear defrost button burn out, there was a spark and a lot of nasty smells (wires burning) and not the button will not engage the defrost. Any ideas what I need to do to fix this? What caused it?
Wires wear out, fuses burn out. It's just one of those things. Take the car to a good mechanic and let them trace it down. I wouldn't try to do it myself, you may short out a bunch of other stuff.
Sometimes we just have to rely on a mechanic to identify the problem and fix it. We can learn from the mechanic by observation him/her while the car is being fixed. We can also ask questions on what do to when this type of problem reoccur.