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

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 12-20-2011, 11:49 AM   #1
Newbie
 
Join Date: Dec 2011
Posts: 4
Rewards Points: 0
Share |
Default

Testing Voltage @ Switch = weirdness


Hello, first post here. Your help is really appreciated.

Both the light and the exhaust fan in bathroom quit working. Circuit breaker was not tripped but turned it off and reset it anyway.

Opened up the wall switch to check it out. There are (3) three conductor wires in the box. Looks like one coming in with the power, one going out to the light, and one going out to the fan. Black coming in goes to the bottom on the fan switch then jumps over to the bottom of the light switch. All (3) white neutrals are nutted together and all (3) grounds are nutted together.

Using digital multimeter I find this at the switch:
Switch off:
bottom blk to grd = 119.6v
top blk to grd = 0v
bottom blk to wht = 63.2v (is this weird)
wht to grd = 1.5v

Switch on:
top blk to grd = 119.6v
top blk to wht = 59.7v
wht to grd = 6.3v

At the light itself:
Switch off:
blk to grd = 0v
blk to wht = .4v
wht to grd = 1.5v

Switch on:
blk to grd = 119v
blk to wht = 59.3v
wht to grd = 1.5v

Ideas on the problem, how to track it down, how to fix?

Thank you.

anon1 is offline   Reply With Quote
Old 12-20-2011, 12:36 PM   #2
retired elect/hvac/plumb
 
plummen's Avatar
 
Join Date: Jan 2010
Location: south east of omaha/The island of misfit contractors
Posts: 2,911
Rewards Points: 30
Default

Testing Voltage @ Switch = weirdness


check your white wires,sounds like an open neutral to me anyway

plummen is online now   Reply With Quote
Old 12-20-2011, 12:42 PM   #3
Member
 
Join Date: Jun 2007
Posts: 3,506
Rewards Points: 0
Default

Testing Voltage @ Switch = weirdness


Open up the nearest receptacle and find the white neutral connected to it. Measure using this neutral. You may be using a switch leg (white) in the switch box, instead of a neutral. It is entirely possible there is no neutral in the switch box. Using ground for measurements is not a good idea. Everything will work minus the ground. the ground is for safety not operation. Make sure you are using a neutral when measuring and disregard the grounds.
J. V. is offline   Reply With Quote
Old 12-20-2011, 01:36 PM   #4
Newbie
 
Join Date: Dec 2011
Posts: 4
Rewards Points: 0
Default

Testing Voltage @ Switch = weirdness


OK, neutral from an outlet (that is also on a separate circuit) to black at switch shows 120v.

So, the neutral in the switch box is the problem? Shorting or breaking somewhere?

[add] In your experience what is the most likely place of the problem, at the panel or somewhere in between?

Can I run a jumper from neutral in switch box to the good neutral in the outlet to see if the light works?

Thanks.

Last edited by anon1; 12-20-2011 at 01:39 PM.
anon1 is offline   Reply With Quote
Old 12-20-2011, 01:45 PM   #5
retired elect/hvac/plumb
 
plummen's Avatar
 
Join Date: Jan 2010
Location: south east of omaha/The island of misfit contractors
Posts: 2,911
Rewards Points: 30
Default

Testing Voltage @ Switch = weirdness


yes just dont leave it that way
plummen is online now   Reply With Quote
Old 12-20-2011, 01:53 PM   #6
retired elect/hvac/plumb
 
plummen's Avatar
 
Join Date: Jan 2010
Location: south east of omaha/The island of misfit contractors
Posts: 2,911
Rewards Points: 30
Default

Testing Voltage @ Switch = weirdness


If you check just between the black and white feeding the room do you get 120v
Do the feed wires go up or down through wall? if they go down through an unfinished basement you could start looking for junction boxes between there and service panel.
if you can get the lights to come on by temping off another neutral that would eliminate them from the puzzle.
you could also kill the breaker to that room and see if that kills anything else,then youll have a general area to start checking plug /switch boxes for a loose wire
plummen is online now   Reply With Quote
Old 12-20-2011, 02:41 PM   #7
Newbie
 
Join Date: Dec 2011
Posts: 4
Rewards Points: 0
Default

Testing Voltage @ Switch = weirdness


OK, making progress.

I put a jumper between the bundled neutrals in the switch box over to the neutral in the receptacle box and the light worked.

As soon as I flipped the switch this tripped the GFI circuit breaker in the panel that feeds the receptacle that I was jumped into. That sounds reasonable.

I unbundled the neutrals in the switch box and tested black to that single white and got 22.6v.

There are only two other lights on the circuit, looks like it comes out of the panel, hits the light in the utility room with the panel, then up to the light in the attic, then over to the bathroom with the light and exhaust fan. Both the util and the attic light still work so best guess would be that the problem is when coming out of the attic light over to the bathroom switch box.

I guess it is time to get up there and check it out. I'm just thankful that it isn't summer and 120* up there.

Thanks a lot for the help.
anon1 is offline   Reply With Quote
Old 12-20-2011, 03:17 PM   #8
retired elect/hvac/plumb
 
plummen's Avatar
 
Join Date: Jan 2010
Location: south east of omaha/The island of misfit contractors
Posts: 2,911
Rewards Points: 30
Default

Testing Voltage @ Switch = weirdness


plummen is online now   Reply With Quote
Old 12-20-2011, 03:50 PM   #9
Newbie
 
Join Date: Dec 2011
Posts: 4
Rewards Points: 0
Default

Testing Voltage @ Switch = weirdness


Couple other question, if you don't mind?

What would be the best way to replace this 12/2 g nm going from one fixture through the attic down an interior wall and into the switch box?

Cut it at some point in the attic, test it from that point to the switch, if still not good then move closer to switch some more and cut/test again, until the bad spot has been cut out? Then splice in new section from there back to upstream fixture? Not sure about what is safest and within code. Obviously the splice would be inside of a plastic box.

My only concern with replacing the entire run from the switch on back would be getting the new wire through the wall and down into the existing switch box.

How about taping the end of new cable to the end of the existing at switch and pulling it up into the wall to the attic? Does that usually work? I guess mainly the hole in the switch box and the hole in the top plate of the wall would need to be large enough to get two widths of cable through.

Last edited by anon1; 12-20-2011 at 03:52 PM.
anon1 is offline   Reply With Quote
Old 12-20-2011, 03:59 PM   #10
Electrical Contractor
 
jbfan's Avatar
 
Join Date: Jun 2004
Location: Newnan GA
Posts: 5,795
Rewards Points: 22
Default

Testing Voltage @ Switch = weirdness


Rarely will you find a bad wire.
Most likey it is a connection at one of the fixtures that has become loose.
__________________
Yes I am a Pirate, 200 years too late. "Jimmy Buffett"
jbfan is online now   Reply With Quote
The Following User Says Thank You to jbfan For This Useful Post:
SD515 (12-21-2011)
Old 12-20-2011, 04:01 PM   #11
retired elect/hvac/plumb
 
plummen's Avatar
 
Join Date: Jan 2010
Location: south east of omaha/The island of misfit contractors
Posts: 2,911
Rewards Points: 30
Default

Testing Voltage @ Switch = weirdness


check the conection inside the fixture thats feeding from the attic to the bathroom ,dont cut wires between boxes.
plummen is online now   Reply With Quote
Old 12-20-2011, 06:55 PM   #12
Member
 
Join Date: Feb 2010
Location: Oklahoma
Posts: 978
Rewards Points: 0
Default

Testing Voltage @ Switch = weirdness


Quote:
Originally Posted by jbfan
Rarely will you find a bad wire.
Most likey it is a connection at one of the fixtures that has become loose.
True...unless there happens to be a rodent nearby. I've seen lots of gnawed neutrals. Odd thing...it seems they have the ability to know to NOT chew on the black wire. Smart critters, but nasty. I hate mice and rats.
jlmran is offline   Reply With Quote
Old 12-20-2011, 06:59 PM   #13
Electrical Contractor
 
jbfan's Avatar
 
Join Date: Jun 2004
Location: Newnan GA
Posts: 5,795
Rewards Points: 22
Default

Testing Voltage @ Switch = weirdness


Quote:
Originally Posted by jlmran View Post
True...unless there happens to be a rodent nearby. I've seen lots of gnawed neutrals. Odd thing...it seems they have the ability to know to NOT chew on the black wire. Smart critters, but nasty. I hate mice and rats.
I never want to infer someone may have rats!

I did ask a customer one time if they had mice.
You could see the droppings everywhere.

I thought that I was going to find a chewed wire, from the mice, but found out it was the dog!!!!!

My wife made me undress outside that night.

__________________
Yes I am a Pirate, 200 years too late. "Jimmy Buffett"
jbfan is online now   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
B&S Generator with Connecticut Electric Xfer Switch Rick5150 Electrical 19 01-20-2011 10:14 PM
3-way light with a twist Jeepsail Electrical 14 05-18-2010 01:24 AM
End switch voltage Joe F HVAC 4 03-13-2010 06:06 AM
3-way switch help amit Electrical 17 02-15-2010 03:17 PM
Phantom voltage reading on switch loops jamiedolan Electrical 5 02-09-2009 04:22 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.