single wire alt

[kglowacky]

Took my oem alt to get it tested at a very reputable alt shop/ It tested 14.2 . He said all good. My problem is it charges at around 13 at idle but when I turn on my a/c the eclectic fans it come on and it drops to around 11.5. Turn the ac off back to 13. He says I need a bigger gauge cable from alt to battery. says 4 gauge I currently have the factory 2002 Camero cable on it BUT I did splice it to make length. After talking awhile he says either to small of cable or need bigger amp alt. factory is 100 he says he can sell me a 175, My question is does this sound correct ? And what does that single small wire do? He says he can eliminate it completely. I don't like eliminating any factory wires.

a thought I have. My battery positive cable is a 3 wire molded side mounted cable. Factory specs. Right now one wire goes to fuse box one to alt and one to starter, Instead of changing out the alt wire to a larger one and having a challenge at the battery on how to add this thicker cable why can't I just add another wire the same thickness as oem run it from back of the alt as my current one to starter this way I have duel cables going to battery and I dont have to screw with the battery post connector.