The functioning of fuses can be checked from the holes in the fuse’s cover. If the metal strip visible in the hole is unbroken, the fuse is operational.
If the metal strip is damaged, meaning that an overload has occurred, contact a qualified nautical electrician.
Opening the cover is not recommended, as there is a danger of electric shock and serious injury.
If the metal strip is damaged, contact a qualified nautical electrician. If it is necessary to open the cover, make sure that all the current cables from the batteries are disconnected.