rx slim

I have a 1994, and this electrical problem is driving me nuts. My problem started quite a while ago, when my lights were left on and I had to jump the car. Everything was fine for a short while, but then the battery died again. I charged the battery, but continued to have weird problems with the alternator light, along with about every other light in my dash, and the car running really rough. I replaced the alternator and battery, car ran fine for about a week. Then the same problems came on with rough ride and lights in dash. I inspected the harness into the alternator and both wires are frayed and fairly corroded as they come out of the harness, so I figured maybe they are shorting each other. (I believe these are L and S in the shop manual). The bottom wire "L" was so corroded it broke as I was messing with it. Now when I start the car it runs great, with no light problems, but as I connect L back together by toughing the frayed end to the harness problems immediately return. I don't think I can just leave it disconnected, but I'm not really sure what the real problem could be. Sorry so wordy, but I wanted to give a good description if anybody has encountered this before. If I replace it with better wire would it solve a resistance issue and probably run fine?? Or could it be another problem altogether. Any help is greatly appreciated.