Usually in your owner’s manual there is an illustration that identifies the location for all the fuses in your car. The fuse box is usually in the engine bay, under the dashboard, behind the glovebox or behind a kick panel in the footwell area.

Each vehicle system is briefly described along with the illustration. If you remove a fuse, the associated system will become inoperable since the power source has now been disconnected.

Most navigation systems will not impact normal engine operation or influence any critical safety systems. Your dashboard will probably indicate that something is wrong and your navigation and map displays will not work properly.

Regarding the fuel shut off, once you identify the fuel pump fuse, you can trace the wires as they enter or leave the fuse box. You can interrupt the electrical circuit by installing a switch in that wire either before the fuse box or after. Sometimes it can be difficult to get the fuse box loose to locate the wires behind it. So alternatively, you can solder a switch across a fuse that is already blown (open circuit). It’s important that you also wire in a good fuse with the same amperage as close to the fuse box as possible (on the same circuit as your switch) since you removed the original. Make sure you use shrink tubing on all the connectors so that nothing can short out. The system is only 12 volts DC so it can NOT electrocute you.

This guy sort of did a hack job by wiring in a switch at the fuel pump in the back of his car. It’s perfectly okay to put the switch anywhere in the circuit where you have easy access. I just prefer to do a cleaner job so I can easily remove any modifications when I go to sell the vehicle.