Wiring Harness to Trunk
 

If you're certain it's wire abrasion, and you're able to track it down, you can fix it without soldering...get a pair of DT connector sets, some shrink tube and possibly some heavy-duty loom (not the cheap corrugated split stuff, look at wirecare's website for the good stuff), rent the tool, and you should be able to replace the abraded section in an afternoon. Use tinned, stranded automotive hookup wire, and it should be fine.