So i got this van that’s already built out a bit and the owner before has a second battery and solar in it. Theres a switch under the steering wheel that if it’s on when I start the car it shows a red battery so it has to be off then. I have a T4 so the fuzes are there too. I forgot the use of the switch though besides i got to have it on off when I start the car or so tje previous owner told me at the time. I forgot the rest thought what he said about it. Anyone else has an idea what it could be?