I just recently swapped out my stock alternator for a mechman 220amp alternator and fits fine but a new problem has came up. Before I had my uncle install the new alt the electrical was running smooth. While installing the new alt, I saw a bunch of smoke coming from the battery positive wires and saw a small wire completely burnt in half. He was an idiot and did not disconnect the negative on the battery before performing any work.While he replaced that wire, I am now having gauge problems. The voltage at the battery and at the alternator are ideal running at 13.8-13.9v. However, the gauge inside the car reads less than 12v while running and the car is not receiving enough current to run correctly. It runs rough and the lights flicker at night. What are possible causes for this to happen?

 

sounds a little like it could be a bad ground to the body to me

 

I just remembered that another wire he fried was a ground to the body and has not been replaced since. Hopefully this is a simple fix. Thanks.