Alternator failure
 

Has anyone had there alternator go out and start overcharging?

Take away it's credit card maybe?

no but it isn't unheard of for that to happen to an alternator especially if the internal regulator is shorted. you can use a fluke meter to determine this by hooking up the leads to the hot post on it and to ground

+1

@OP: If you can use a multimeter, the FSM should have testing procedures to isolate the problem. If not in the FSM, the general procedure is the same for most cars and should be in the Chilton (or similar) books you can find at auto parts stores for recent Nissans with V-6s.

What makes you think it is overcharging? High reading on dash voltmeter? Burnt up battery? Something else?

Or you can take it to one of the auto parts retailers (Advance, PepBoys, Autozone, O'rielly's, etc) and they will check it for free.
My voltmeter always indicates slightly over 14 volts but I believe all is well because I haven't had any other indications of overcharging. (Voltage should be approximately 13.8 volts on a properly charging system.)

Why do you think it's over charging?

The voltmeter can occasionally read as high as 15v., if that's what you are going by.

In a post a few month back, I found a 10 AMP fuse #32 (12 volt input to the ALT) open and causing a over-charge at 14.7-15.0 volts as well as a E-Brake lite. I chaged the fuse and the proble went away. Fast foward problem is back but now the fuse is good. Advanced auto just checked the ALT and is is Good. After inspecting the wiring I found some small cuts in the insolation at the 3 pin connector. All this is caused by my year long boost problem that was a bad tune from GMT... I had the SC in and out of the car no less than 6 times in the year of pain. I must have damaged the wires...

You can read about the "Missing Boost" post
http://www.the370z.com/forced-induct...ing-boost.html

And "Battery Overcharging"
http://www.the370z.com/engine-drivet...er-charge.html

When the system works correctly I see 13.5 ish on my Dightal Volt meter.

According to page CHG-27 of the 2009 FSM:
and
The 13.5V you are reading is probably the fully-charged battery voltage (~13.2V) plus a few tenths due to meter accuracy.