Hi Guys, A bit of a troublesome issue so I will try to go through my situation step by step.

I have a 2005 V6 5-speed mustang. About 90K Miles. Ive owned the Car since 2010.

About 2 months ago While cleaning under the hood I noticed a little squeak and that the Serp belt was showing heavy signs of wear. I decided to change the Serp belt, Idler Pulley and Tensioner.

The noise went away and all was fine, About 2 weeks later while driving I noticed the Battery light come on, which I have never seen in my car before.

I decided to get a new battery and OEM Alternator as the car was getting up there in miles and the Battery was around 6 years old.

I swapped out the Battery and OEM Alternator and the light went away and everything seemed fine. A week later I came out to my car( it is my second car and I drive it usually a few times a week) and the battery was completely dead. Not even enough to unlock the doors. I Charged up the battery and put it back in but when I did the Battery light was back on and it seems to drain the battery completely now every 48-72 hours.

I double checked and I don't have anything on that could be draining the battery ( Lights, Radio ETC)

Could this be a ground issue? Possibly a fuse that popped that is causing the drain?

Any info would be greatly appreciated