Unplug from shore power and take a voltage reading across the battery and write down or remember that number.
Take a voltage reading from the positive terminal of the battery to a good ground somewhere on the frame. You should get the same battery voltage measured above.
Now follow the positive wire from the battery and check the voltage to ground on both sides of any fuses or breakers you find.
All your measurements should be within 1-2 tenths of a volt from what you measured at the battery.
If not within 1-2 tenths of a volt, or if you have battery voltage on only one side of a fuse or breaker; That is a blown fuse.
Keep working back to the panel until you find the power isn't there.
