Parking Brake Tensioner Nuts Are a B#$%^!

Wire brush the threads on the adjuster to remove as much corrosion as possible since that will jam up the threads. you will have to alternately tighten and loosen the nut as you go a little more each time you loosen. And use lots of penetrating oil. I would start by tightening the nut back up off the threads that are trying to jam it up, then clean the threads off as well as you can before proceeding. I would recommend using 2 stainless steel nuts to use as jam nuts, and some anti sieze when it goes back together, or just buy a new cable from rock auto.