Location of the fuse depends on the purpose for the fuse.
If you are trying to protect from an "overload" condition, then anywhere in the circuit will work. An example of this is a 10A fused accessory outlet intended for a radio or a GPS. Normally, everything would work fine. When you plug in an electrical defroster that draws ,say 20A, the fuse will blow and protect the wiring from overheating.
If you are trying to protect from an accidental "fault", then the closer the fuse is to the source (i.e. battery or higher current fuse feeding several smaller fuses) the better. For instance, you may pinch a wire going to the relay or accidentally place a screwdriver across a live circuit. The shorter the unfused wire from the battery to the fuse usually means less opportunity to cause damage further upstream.
Puting the fuse closest to the source does both. It protects better against accidental faults and protects from overloading. So this is usually the choice made.
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Chuck.
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