Pen Tester False-positive? - Electrical - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical


Thread Tools Display Modes
Old 03-05-2011, 08:35 AM   #1
Join Date: Feb 2010
Posts: 7
Rewards Points: 10

Pen tester false-positive?

I was rewiring a wall switch to vanity light in my bathroom to remediate a code violation. Previous wiring (code violation) as follows: 12-2 wire going from switch to buried junction box where it was spliced to new 12-2 wire which went to the light. New wiring I connected goes directly from wall switch to light (no buried box). Just for giggles before closing everything up, I voltage pen tested the "discontinued" wire and the meter continuously beeped when I turn the newly wired switch on AND the adjacent but separate wall switch for the bathroom fan on. If one or the other were on, the pen tester didn't sense anything. It also did not sense anything if I touched the wire 12-2 wire insulation with my other hand while pen testing. I know for a fact that this wire was disconnected on both sides of the buried junction box. How is the pen tester getting current and why when only with both switches on? Is it static from the other lines/operating fan? I did not have a meter tester so I hooked up a light to it and whatever voltage there was could not power the light. So i taped it, labeled it discontinued, wire nutted them, and left them in the wall. Is this ok?


campbesh is offline   Reply With Quote
Old 03-05-2011, 11:37 PM   #2
Scared Electrician
Saturday Cowboy's Avatar
Join Date: Nov 2009
Location: Colorado
Posts: 715
Rewards Points: 500

Pen tester false-positive?

pen testers are dangerous if not well understood. I do not recommend them for troubleshooting at all.(they aren't a troubleshooting tool). They do one thing only: Is there power? they are unable to reliably answer the question: Is it dead?


Ragged Trousered Philanthropist

Please follow the code - its there for your safety no matter how inconvenient.
Saturday Cowboy is offline   Reply With Quote
The Following User Says Thank You to Saturday Cowboy For This Useful Post:
campbesh (03-06-2011)
Old 03-06-2011, 07:38 AM   #3
Join Date: Feb 2010
Posts: 7
Rewards Points: 10

Pen tester false-positive?

I appreciate your reply. I have gathered as much about pen testers after doing some additional research. Wish I would have ran out and got a multimeter before closing everything up. I'm 99.9% sure everything is safe, just perplexed by the situation and wondering if anyone could provide reassurance or specific explanation.

Both ends of the line were cut from power/devices and would only set the pen tester off when many other devices were on in the area. As I said before, the pen tester would turn off when I touched the dead line with my other hand. It would not power a 3 light vanity hookup either so I am going to leave it as is. Just kind of thinking out loud here. Thanks!
campbesh is offline   Reply With Quote
Old 03-06-2011, 11:11 AM   #4
Join Date: Jun 2007
Posts: 3,585
Rewards Points: 2,158

Pen tester false-positive?

Homeowners benefit more from solenoid testers. Multimeter's for DIY'ers serve only to confuse.
By one of these. Cheap, reliable and indestructible.
No contact testers can cause serious injury and or death if used improperly or used by the uninformed.
This tester has a solenoid inside it. When the probes come in contact with power the solenoid shifts making a distinct noise and has a distinct feel.
Attached Images
J. V. is offline   Reply With Quote

bury dead wires , pen tester , voltage tester

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Circuit tester shows open neutral; multi-meter says something different. fredgmeyer Electrical 11 10-26-2009 12:41 PM
Replace exterior walls or build false walls Medic507 Carpentry 3 11-12-2008 09:48 AM
False beams dofin Carpentry 4 01-27-2008 01:49 PM
Clamp on Amp Tester Help stagger19 Electrical 3 03-07-2007 08:26 PM
Positive, Negative sides calabashfire Electrical 10 09-25-2006 06:29 PM

Top of Page | View New Posts