Were it mine , I would start out by doing the following ;
Get a volt / ohm / amp meter . Cheap one is ~ $10 at Harbor Freight .
Visually inspect as much of the wiring as you can see .
Have the alternator inspected / check it yourself . May have one or more bad diodes .
If it has a cigarette lighter , unplug it . Any USB charger plugged into the cigarette ?
Make sure the trunk & under hood lights go out when they are closed & not burning 24/7 . Make sure the interior lites go out when the doors are shut .
Any aftermarket accessories connected to the electrical system ( trailer brake controller stereo head end ) .
Remove the negative cable from the battery with a full charge on the battery . Measure the voltage and amperage drain ( key off & and out of the ignition ) between the negative battery post and the negative battery cable . Write this down and record the data .
With the VOA meter connected slowly remove fuses one at a time , watching and recording the data for both volts and amps . Does the removal of any one fuse produce noticeable change ?
Report back with what you find .
God bless
Wyr
