I have a 1941 1/2 ton pickup. My new battery keeps going dead after two days of not starting the truck. Now I've had the battery checked by three different stations and each of them said the battery, 8 volt Interstate, is fine. I have replaced the starter, generator, regulator, all cables and grounds, checked to make sure the lighting switch, heater switch, defroster switch, fog lamps, brake light switch, and spotlight are not on. They are not. I am baffled and need help.Thank you so much. ps I have installed a battery cut off switch for now.