I am pulling my hair out trying to chase down a voltage loss or short or amp draw...not really sure what it would technically be called. I have a brand new battery as of a month ago, in which the old battery truly was bad. The car has run great for the last month, and now it just won't hold a charge...just sitting still. I will fully charge the battery and it will read just under 13V steady for a few hours.
It fully charged by 5pm yesterday to just over 13V...it settled and held 12.7 to 12.8V until 7am this morning. When I got home this afternoon...BOOM 3.7 volts and I could watch the voltmeter slowly "counting down". I posted yesterday about a mystery plastic part that was laying under the car...it was the starter post cover. Popped it on and hasnt made a difference in holding or loosing charge.
I have visually inspected and tested resistance through the box on top of the battery...and nothing is melted or out of whack that I can tell. One other weird thing; when the voltage was where it needed to be, the auto-window-crack feature was wonky. It would drop the window down, but put it right back up. Once the voltage nosedives, the windows do what they should. Even at 3 to 4V the cluster LED's work ok, but obviously it won't crank, headlights won't come on etc.
Any thoughts...I am about to set fire to it.