Pull the switch out turn it on and test the terminals with a voltage tester.
How to install a light switch in an existing wall.
Adding an electrical box to your existing wall for a switch or outlet is easy when you have the right materials and know a few tricks.
Unscrew the wire nut holding the two white wires together.
Remove the cover plate from the existing light switch.
Shop all lighting now.
Unscrew the wire nut holding the two black wires together on your existing light.
Remove the two 6 32 screws securing the switch in the box.
Start the light fixture installation project by turning the power off at the main electrical panel unscrewing the switch and pull it out the switch.
The switch comes first in the new part of the circuit and new 2 wire cable is run to it from the outlet.
When you need to add an outlet or switch in an existing wall you need to use a special electrical box called an old work box an old work electrical box may be metal or plastic and is specially designed to be installed in an existing wall where it has no support other than the wall itself.
Twist the wire nut onto the three wires to secure them.
Pull the switch from the box and loosen the terminal screws slipping the circuit.
From the switch new 2 wire cable is run to the new light location.
Wiring a new switch and light from an outlet in this diagram power is taken from an existing wall outlet for a new switch and light fixture.
See the video above for more specific instructions.
If the wall is heavily insulated push conduit through the insulation and then feed wires or cable through the conduit.
Strip the last one inch of your new black wire and place all three black wires together.
This project guide will walk you through the process of installing the switch including wiring both the switch and the fan.