You should wire any cut off switches into the negative side of the system.
That is whty whenever your working on the electrical system it is recommended you disconnect the earth.
I have seen a car burn out its wireing harness when the positive battery cable was disconnected.
Allways disconnect earth first and reconnect earth last.
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Cruising in 5th
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Never be afraid to do something new, Remember, Amateurs built the Ark: Professionals built the Titanic.