How to Wire 12V Accessories to a Toggle Switch

Written by teeter allen morrison
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How to Wire 12V Accessories to a Toggle Switch
Some switches illuminate when they are in the on position. (toggle switch image by Sergey Danilov from

When wiring a 12-volt toggle switch to an accessory consider a couple of things. Mount the toggle switch in a neutral area, an area away from things like the turn signal lever, the door locks and the window switch. This will help prevent the switch from being turned on or off by accident. It's also important to mount the switch within easy reach. Another important consideration is the type of switch. A low profile illuminated switch may be a good selection. Consider a switch that only requires a small drilled hole for mounting purposes.

Skill level:

Things you need

  • Safety glasses
  • 12-volt test light
  • Wrench set
  • Drill motor
  • Drill bit set
  • Two-post toggle switch
  • 12-gauge wire
  • Screwdriver
  • Wire ties
  • Wire crimp tool
  • Wire ends

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  1. 1

    Mount the accessory to be wired in a desired place. Crimp an eyelet onto the ground wire of the accessory. Run the ground wire from the accessory to a metal frame or bracket under the dashboard. Remove the paint from the intended ground area so the ground wire is attached to bare metal.

  2. 2

    Drill a hole in the selected area where the toggle switch will mount. Crimp a wire terminal on the end of the 12-volt power wire for the accessory. Be sure the power wire is long enough to reach one spade on the toggle switch.

  3. 3

    Select an open accessory spade in the vehicle's fuse box that has power and is hot when the key is on. Check the spade for power when the key is in the on position and no power with the key in the off position, using the 12-volt test light.

  4. 4

    Crimp a terminal on both ends of a 12-gauge wire long enough to go from the fuse box to the mounted toggle switch. Be sure to allow enough wire length so the wire may be routed and wire-tied in a neat fashion under the dashboard.

  5. 5

    Connect the hot wire terminal from the accessory to an open spade on the power-out side of the toggle switch. Connect one terminal end of the 12-gauge wire to an open spade on the accessory side of the fuse box. Connect the other terminal of the 12-gauge wire to the remaining open spade on the toggle switch. Use wire ties to secure accessory wires to other wire looms or brackets.

  6. 6

    Turn the key to the on position. Flip the toggle switch to the on position; the accessory should now be powered. If the accessory worked as intended, turn the key off. Push the toggle switch through the drilled mounting hole and thread the nut onto the switch to secure it to the mounting hole. Tighten the switch nut with a wrench while holding the back of the toggle switch.

Tips and warnings

  • If the toggle switch has screw mounts instead of spades, substitute the wire terminals with eyelets on the wire ends to the toggle switch.
  • The fuse box is usually located in or around the steering column under the dashboard.
  • Select an open spade in the fuse box that is hot all the time if the accessory is to be used when the automobile's key is in the off position.
  • If the toggle switch is an illuminated switch and it does not light up when in the on position, switch the two spades on the back of the toggle switch because the switch may contain an LED light.
  • Always wear safety glasses when working in or around automobiles.

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