12 volt question

[Squishman]

If a guy has a 12 volt device with battery clamps as opposed to a cig lighter plug (it's an electric scissor jack) with a 15 amp in-line fuse, but that fuse is on the negative wire, does the fuse protect the device and/or wiring, or only if it's on the posi wire?

 

[Speedskater]

Sometimes yes and sometimes no.
a] if something inside the device fails and the device draws lots of current ~ YES
b] if the Hot wire shorts to the device's metal chassis and the metal chassis touches the vehicle's metal frame ~ NO

 

[Squishman]

Sometimes yes and sometimes no.
a] if something inside the device fails and the device draws lots of current ~ YES
b] if the Hot wire shorts to the device's metal chassis and the metal chassis touches the vehicle's metal frame ~ NO

Oh that makes sense. Thx.