Wife called from work and said her brake lights were stuck on and would not go out. I advised her to go by parts store and pick up a brake light switch. On her way to parts store she called back and said smoke was coming out from under dash, I called my mechanic and told him, he rushed down there where she had pulled over. He said when he got there and got the battery lead off, smoke was boilng out of car. When he checked switch and the connector it plugs into, both were completely melted, red hot and wires burnt off. My question is two fold, 1st what would have caused this and 2nd why did it not blow a fuse before it got this bad ? Mechanic said it had two wire back to fuse box but no fuses blown.