Fault In Old Bx 2 Wire Cable Switch Loop - Electrical - DIY Chatroom Home Improvement Forum

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


Thread Tools
Display Modes
Old 10-25-2009, 12:57 PM   #1
Join Date: Oct 2009
Posts: 1
Rewards Points: 10

fault in old bx 2 wire cable switch loop

Old BX 2 wire cable rubber insulation/cloth. changed a light fixture. after completing installation with the switch off I started putting in the light bulbs-- lights flikered! voltage test showed 85 volts in the switch loop when switch is off. I know there is a fault in the switch loop. Did a continuity test in the switch box but no continuity. when breaker is off- no voltage so there is no other source. Just want to know how a lower voltage such as the 85v read I have slips thru "evidently poor" insulators without the conductors actually "completely touching". If there was good contact in this case the lights would have stayed on. any master electrician or journeyman who knows please reply. Thx. (PS I took out the switch loop- naturally)
scire is offline   Reply With Quote
Sponsored Links
Old 10-25-2009, 01:16 PM   #2
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 8,716
Rewards Points: 3,038

Rubber insulation can biodegrade into brittle chips or powder. The wires themselves become superficially oxidized over time. Rubber, which contains sulphur, actually hastens "oxidation" of the wire surface. So wires can touch making electrical contact but not a good contact.

If you have a fault in a cable of any vintage, you are going to have to replace the cable. Now if you know where the fault is, for example you put a nail through the cable, you can put two junction boxes there (one if the cable has enough slack).

Don't forget, when measuring voltages, measure between a switch terminal and neutral (with some intuition, you can make sense out of measuring from the switch terminal to ground). Don't measure between the two switch terminals.
Stop some of your bank autopayments so you can set priorities for manual monthly payments out of your coronavirus stimulus check.

Last edited by AllanJ; 10-25-2009 at 01:23 PM.
AllanJ is online now   Reply With Quote
Sponsored Links

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
What is the est way to wire up a switch and light.... jailbird371 Electrical 5 05-30-2009 08:24 PM
Installing timer switch, no ground wire in switch box diydan Electrical 2 05-25-2009 07:51 PM
Will reverse polarity trip breaker?? Duane 70 Electrical 60 12-05-2008 10:18 PM
Wire Multiple Lights controlled by 4-way Switch? mfleming Electrical 17 11-20-2008 08:46 AM
Overhead light w/ switch and 3 recept. how to wire? twilightcall Electrical 8 01-07-2008 04:27 PM

Top of Page | View New Posts