Problems With An Old 1930 Dimmer Switch Wiring - Electrical - DIY Chatroom Home Improvement Forum

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


Thread Tools Display Modes
Old 02-27-2011, 09:52 AM   #1
Join Date: Feb 2011
Posts: 1
Rewards Points: 10

Problems with an old 1930 dimmer switch wiring

I am trying to replace a chandelier dimmer switch. Only one switch controlled the lights (120v) and at one time it worked to turn on and off and dim. The owner threw away the old switch. There are only two wires exiting the box, one is at ground potential and the other(both black fiber wrapped) is at 5.4v ac. A standard single pole switch does not work, neither wire is 120v. I assume there is a transformer somewhere in the wall. If I place the 5.4v wire to ground, nothing happens. Any ideas about the wiring of this circuit?


DouglasMcKibbin is offline   Reply With Quote
Old 02-27-2011, 10:33 AM   #2
Join Date: May 2010
Location: Miami, Florida
Posts: 192
Rewards Points: 150
Send a message via Yahoo to sparks1up

I suspect the wire that is grounded was the hot feeding the light switch and it is shorted somewhere.

If there are only 2-wires in the box it would have to have been a hot and a switchleg. Since you have no power there I would have to guess the wire that has 5.4V is the switchleg and the other was the hot because there is no reason for a neutral to be in a switch box. I suggest you trace that wire, it may go to the light and be shorted there.

It is not uncommon in older homes wired with old style BX cable that has cloth covered rubber insulated wiring to short right where it enters the box. This is because they used shallow pancake type boxes for ceiling outlets and the wire is usually bent sharply where it enters. This was not a problem when the wiring was new but now the rubber is dried out and crumbling leaving the copper exposed. There is no reasonable and safe way to repair this situation other than to replace the affected cables. This quite often leads to replacement of the entire circuit/s because as you take apart one splice the insulation starts to crumble on all the wiring.

If you are lucky and the house is piped in you can repull but if it is BX you will have to cut and fish.

I have also seen in older homes where the neutral was switched, but you said a single pole switch didn't work so that is not the case.

Good luck!


Answers based on the mood I am in when you ask!
sparks1up is offline   Reply With Quote

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
Changing from dimmer to regular!!!!!!!!!!!!!!!!!!!!!!! Gomezy3k Electrical 8 10-04-2010 03:26 PM
Switch on K&T wiring - OK to pigtail? fdmillion Electrical 4 01-27-2010 09:15 AM
Hunter Fan Dual Switch Wiring Configuration Help schierle Electrical 2 03-29-2009 08:00 PM
Basic Switch wiring question; Dimmer to Toggle switch (Pictures included) inspectator Electrical 8 08-07-2007 01:19 AM
Dimmer Switch Problems? dmtm21 Electrical 2 08-07-2007 01:18 AM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1