ramairetransam

iTrader: (18)

I start the car up and it runs at 13.8-14 volts , as soon as i get driving the car it goes to 13 and then with the ac on its usually below 13 at like 12.5-12.7

Why does it start off so high and then get lower , if the alternator bad , the battery is brand new . I heard one time that something in the tune to due with the alt , maybe it was an alt/idle thing . Any truth to that .

I assume i need a new one but figured id ask about something in the tune , and its far fetched but i thought their was something in hp tuners that delt with the alt like a threshold or some sort.

jimmyblue

iTrader: (11)

I used to see this when my car was stock, the alt voltage
would sag once I started running the A/C to the point that
it would make the car start to idle rough. This seemed to
be thermal related, only really did it in summertime. Once
I started running the fans full time it kind of went away,
engine bay is definitely cooler that way.

But you might look at the grounds, A/C clutch dumps
current into the block and might jack the alternator
reference hence output somehow, etc, fans dump current
into the harness somewhere and so on. It all needs to be
tight to keep good regulation (even if the alternator is
correct in itself).

Try measuring alternator voltage from the stud to the case,
to see about that. Maybe the alt is good and the problem
is in the chassis sheet metal, where the voltmeter picks up
its reference ground. Or something.

wssix99

iTrader: (5)

The electronc components in the alternator could be past their prime. If you take it to a parts store, they can test it and confirm.

ramairetransam

iTrader: (18)

yeah , well im procharged and dont wanna have down time , its a pita to take the procharger off , so if im taking the alt off im gonna buy a new one or a reman .

wssix99

iTrader: (5)

The alternator removes underneath the car. Do you really need to remove the supercharger for that?

If it is going out, your fortunate to get the advanced warning.