What can cause this?
 

while driving i see my battery light blink, so i look at the gauge and its reading High, So i turned my brights on and after a few seconds it was back to reading normal.

What would casue this?

Bad alternator perhaps. Seems to me like the alternator is over charging the battery. Its a regulator or something like that that goes bad inside the alt.

Its a brand new Alt.

Brand new, or remanufactured?

The Mustang gremlins! You need to get a catholic priest to perform an exorcism to kill those little bastards. But make sure you protect your ass while it's all happening. :)

lol +2 but if its brand new theres gotta be a warranty, take it back and get a new one

I agree, thats almost certainly a bad regulator in the alternator. nothing to do about it but replace the alternator. depending on when and where you got it, you should have some kinda warranty on it.

its new and got a warrenty. Taking it back this weekend.

i have serious gremlins...i hate those bastards. i'm just about to give up and sent it off to be excorsized ( the mechanic).

Have you run a voltage test? A multimeter can be a diagnostic friend...

Or just sprinkle some holy water on it (probably not while the car is on though) :D