Light Switch Has 4 Wires

A light switch has 4 wires sometimes – 2 white and 2 black wires. The whites are connected together with a short third wire; which is called a pigtail, connecting to the silver screw on the pull chain fixture. The blacks are also connected to each other with a short wire, another pigtail, to the brass screw on the fixture.

Remember to turn off the power first.

This indicates a feed-through situation where the power comes to the fixture and continues on to another location. Controlling this light from a wall switch is an easy first time electrical project.

First acquire the proper materials to do this project safely. You will need:

Romex wire that is the same gauge as the existing wire. Never use wire of a smaller gauge than the existing wire, which is usually 14/2.

Wire nuts rated for three wires. Improperly sized wire nuts lead to poor connections. Tighten wire nuts securely and give a little pull to insure a strong connection.

Add a junction box extension, which are readily available and easy to install.

Install the Romex wire from the ceiling box to the switch box by the door. Strip off six inches of the outer shielding from the Romex (do not damage the insulation on the black and white wires) and install into the boxes with a Romex clamp. Plastic boxes require stapling the Romex within six inches of the box.

Strip off about a half inch of insulation from the ends of the black and white wires. In both boxes tape the white wire black (for the six inches) to indicate this wire is being used as a switch leg.

Up in the ceiling box leave the old white wires alone. They will be connected to the white wire of the new fixture, or the silver screw. Disconnect the old black pigtail from the two black wires and attach one of the new ‘switch-leg’ wires. (Either the black or the white wire taped black) Now the white wires will be hooked together and the blacks hooked together. The remaining new black wire in the ceiling box will connect to the black wire or brass screw of the new light fixture.

Move down to the switch box and connect the two wires, one black and one taped black, to the two screws on the switch. You have now just installed a switch leg.

Turn on the power and test your wiring job.

Whenever doing electrical work around the home pull a permit and have your work inspected. This will insure you’re work is safe and sound and that you’ve complied with the local codes.