As I’m going through my research I’ll use this post to document some of the things I find so I have a guide when I go back to do the wiring for real.

Wiring a kill switch

A kill switch must be wires such that it cuts off both the battery and alternator. If it only breaks the battery then the engine will still run if the engine is running, which can spike the system and damage electronics.





Power supply-red

Power ground – black

Sensor supply – orange

sensor ground -green

remaining- white


  1. Generate component listing
  2. Determine needed connectors

Power Supply

  1. Group components into those that need 12v power supply
  2. Group those into 3 categories
    1. Main power- need power regarless of if engine is running
    2. Enable power- only when engine is running
      1. the positives should be powered by output of the main relay to prevent backfeeding
    3. Fuel pump/other- need to be switched on and off
  3. Size wires (current/resistance= peak draw)
  4. Determine fusing for these components
  5. FD3S Power Supply Sketch from HP Academy
    FD3S Power Supply Sketch from HP Academy Practical Wiring Course


  1. Goal is to eliminate having multiple ground paths. This will prevent gremlins when something fails. Star point earthing
  2. You can have two star earthing points but if so, components can only be connected to one or the other not both. i,e, the block and chassis joined by a 2awg ground strap, then one is connected to battery negative. It’s recommended to use the block for all grounding except where impractical(fuel pump)
  3. List all components that need grounding
  4. Size ground wires. Typically power supply and ground are the same, except where one ground supplies two things.

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