Testing Electric Light Switches
Can a Light Switch Leak Voltage? Light Switch Circuit, Voltage Tester Readings and Explanations.
Testing Light Switches
Electrical Question: Can a Light Switch Leak Voltage?
- I wired a single pole switch to a fluorescent fixture in my garage, and with the switch off, and power restored.
- Now I get a faintly lite bulb in my bulb tester if I place one probe to the top and bottom screws. Does this mean the switch is leaking?
- Is it normal for new switches to do this? I have wired three different new switches, all do this. Should I be placing a tester probe on the ground and then the upper screw to test for a faulty switch? I have ensured that the black wire (hot) wire from my panel is on the bottom screw.
- The black feed wire to the light is on the top screw of the switch. The two white wires are wire nutted together properly. The bare copper wires go to the switch’s green ground screw. The ground wire is also pigtailed to the metal box I have it all in.
Electrical Wiring at the Light Fixture:
- I have white to white
- Black to black
- Copper ground to the metal fixture’s ground screw.
Thanks for your electrical wiring question Kevin.
Background: Kevin, a Homeowner from Chapel Hill, North Carolina.
Light Switch Voltage Readings
Application: Testing Light Switches.
Skill Level: Intermediate to Advanced – Best performed by a Licensed Electrical Contractor.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester.
Estimated Time: Depends on personal level experience, ability to work with hand tools and electrical troubleshooting skills.
Precaution: Identify the lighting circuit, turn it OFF and then Tag it with a Note before performing any wiring or switch testing.
The Light Switch Circuit
Voltage Tester Readings and Explanations
- What you are experiencing is quite normal if you are using an analog or no-digital tester.
- If your tester leads are on each screw of the light switch then the tester is actually acting as a switch and voltage is passing through your tester wiring to produce the dim light.
- In reality, your tester is completing the circuit but the amount of current is limited by the internal wiring of your voltage tester.
- If you were to disconnect the line to the fixture ballast you would not get the reading on your tester that you had before because the circuit is not complete.
- This is why it is always good to make your voltage tests to a ground for the best reading.
More about Home Electrical Wiring
Wiring a Light Switch – Diagram 1
Fully Explained Light Switch Wiring Diagrams. Detailed Electrical Wiring Diagrams and Pictures assist your Home Electrical Projects.
Understanding Electrical Testers
- When working on home electrical wiring using voltage testers can play an important part in electrical safety.
- Electrical testers enable you to identify electrical circuits and help prevent the possibility of accidental electrical shock.
Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all Electric Wiring Projects.
The Safest Way to Test Electrical Devices and Identify Electric Wiring!The Non-Contact Electrical Tester
This is a testing tool that I have had in my personal electrical tool pouch for years, and is the first test tool I grab to help identify electrical wiring. It is a Non-contact tester, [amazon.com], I use for the detection of Standard Voltage in Cables, Cords, Circuit Breakers, Lighting Fixtures, Switches, Outlets and Wires. Simply insert the end of the tester into an outlet, lamp socket, or hold the end of the tester against the wire you wish to test. Very handy and easy to use.
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