A couple (maybe few) weeks back, before I went down the rabbit hole of the charging system- I had brought my truck to my yard (40+ mile trip) and (I think) the next day the batteries were dead. Early this morning one of my superintendents was out where the truck is - tail lights were on. He turned the service light switch off. I tried it when I got here - sure enough service light switch on = taillights on. Might have some to do with this rat’s nest of wires a pervious owner created while trying to get a license plate light. We have to have license plate lights for a state inspection for Texas.