ok i just got a new alternator and a battery and i upgraded to 130amp and did 4gauge wire but i noticed when at idle my car runs arround 13.5v and when i turn my lights on and heater and defroster it hits 12 and when i have just lights its 13.4 my question is there has to be something wrong since my friend has a 5.0 and his stock alternator runs at 13.8v i have 2 alternators at 130amps and tried both samething im not shure what it could be. i have a 4gauge power wire connected also. what could cause a power loss? i think maybe a short in a wire or something? also i tested the alternators at kragen and were in working order.