was always having voltage problems. when i first start my car the scanmaster would read 14.1 to 13.9 volts and then when up to temperature the volts would show 12.9 to 13.4 and when i put on the rear defroster and try to use the wondows the volts would show low 12's to high 11's this is my 3rd alternator in 4 yrs and they all showed the same. these are napa alternators. well today i cut off the 10 gauge wire from battery to alternator and put on a stud on the negative and ran a 4 gauge wire from battery to alternator and now my car idles like a dream and the volts dont change even when warm they stay at 13.8 to 14.1 and when i hit the windows they are faster and the astro roof flies. also when i put on the lights and the ac and the rear defroster the volts on the scanmaster drop to 13.5. another thing is the wire stays cold. the 10 gauge wire would get real warm as so did the alternator. i hope this helps