Battery draw down

When the car is cold (overnight), pry the little caps off the top of the battery. Believe it or not, there is water in there to conduct electrical charge. If the water level is low, fill it up to the "full" line and jump start it. Let it run with ALL Accessories (radio, heater, lights) OFF for about 20 minutes. Turn it off and try her again the next day. If she doesn't start again, ti could be the battery is bad, or the alternator, is going out. Either way, a light on the dash usually alerts you to this problem. Any auto parts store can test both the battery and the alternator for you! Best of luck, I hope this helps!

believe it or not I've had this same problem on my 2003 mustang check the plug that goes into alternator and make sure it is fully locking into place mine the locking clip was cracked and it would let the wires wiggle out and cause it not to charge sometimes it looked fine from a glance but after checking everything out with a closer look noticed that the plug wasn't all the way in