97 250da. 2 new bateries Both hooked to switch, both go dead with switch in off position and sitting on a trailer. I did find 3 grounds not connected to the ground post, so got those connected and still goes dead. Any ideas would be helpfull. Changed a bit and tied the 2 together and added a 3rd, stayed out for the weekend limited use of the 12volt system and starts and they are on the way to dead again.