BROWN WHITE Striped wire from the Ignition switch Burnt what can cause this?

[petey-pablo]

I have a quick question My under dash wire harness burnt a couple of months ago I finally got around to replacing it with a new wire harness I spent over $300 for it.. Drove it for the first time the other day and the same thing happen.. The wire that is burrning up is The BROWN WHITE Striped wire from the Ignition switch to the fuse block Any one have any idea of what can be causeing this? I bassicly went through all my wiring since I replaced it but found nothing that could be causing this.. The truck was running fine with no problems prior to the first time it burnt. I cant remember if I did anything prior to this to cause the problem I did change out my fans and wired them up but I dont see how this could have caused it.. I will be checking over my alternator wiring again tomorrow.. Any thoughts of what can cause this or help would be greatly appreciated thanks Pablo....