Slide blows fuze

Have found a schematic on the back of the front cover to the fuse/breaker panel. There are two 40 amp dc fuses in the panel and the schematic says they are reverse polarity fuses. There is no main panel fuse. The 12v from the battery comes to the panel and divides out to 11 circuits to serve the trailer. Can't tell where each circuit goes first, to the controlling switch for that circuit or to the light, motor etc and then back thru the switch. Schematic does not show this. If there is 12 volts at the slide motor then it is obvious that the power goes there first and not to the slide switch. In either case the slide switch will have 12v at one side of the switch, either directly from the fuse panel or thru the slide motor and then to the switch. Only way to tell is check for 12v at the motor. Right? If motor is hot all the time the spurious short has to be before the hot wire is connected to the slide motor. Looks like we have a short pause in our 7 ft of annual rainfall and might have time to do some checking.