smoke and heat. Not good?

[oldschooler]

Hey guys, I have a smoke and heat problem under dash. There is a rectangular little box right above where the steering column goes through the firewall. It has a 3 prong plug w/3 wires in it 1 red, 1 green and a smaller black one. The little silver box is so hot it is starting to melt the plug. Is the box bad or do I have a short some where? If I have a short what accessory would be most likely suspect? Thanks for any input. I would hate to make the old lady happy and have the truck(money pit) as she calls it, catch on fire. Thanks, Rich