Hard to Locate Open Neutral

Reply

  #1  
Old 12-12-10, 05:44 AM
Member
Thread Starter
Join Date: May 2010
Location: USA
Posts: 59
Hard to Locate Open Neutral

The wife said the light didn't work in the laundry room. Since it was a 15 year old T12 fixture I figured the ballast finally went. I installed a new T8 fixture, but it didn't work. I hooked up an outlet and the tester showed "Open Neutral." I then examined the wall box and switch. It has 3 14/2 cables with the whites appropriately wire nutted and the 3 blacks correctly wired on the switch. Although I doubted it was the switch, I replaced it, still no luck.

A guy at Home Depot told me that it was a neutral issue on the same circuit and that I'd just have to check each fixture and switch. He advised putting my meter red lead on the ground wire and black on power, then shutting off breakers until the meter dropped to 5 volts to isolate the circuit, and then check all plugs, lights and switches on the circuit. Problem is that the voltage didn't drop when I flipped all the breakers, so I don't know which the effected circuit is.

Any suggestions would be greatly appreciated.
 
Sponsored Links
  #2  
Old 12-12-10, 07:35 AM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,212
What he was trying to tell you was to check each breaker till the 120 volts goes away and that would be the circuit the light is on. Forget what he said about 5 volts. Your light has to be on one of the circuits, so try again, one breaker at a time till you lose 120 volts to the switch. With just that circuit off, check all other lights, switches and receptacles to find what else is on that circuit. If the 120 volts never goes away, you have two circuits originating from the same hot leg in the panel tied together, somewhere. This makes it more complicated, but you can continue searching for a combination of 2 breakers off that kills power to the switch. You only have to check the 15 amp single pole breakers.
 

Last edited by CasualJoe; 12-12-10 at 07:37 AM. Reason: added info
  #3  
Old 12-12-10, 08:19 AM
Member
Join Date: Dec 2006
Location: orange county
Posts: 285
Smile

Is 120v present, either in your switch outlet box or your fixture outlet box? Note: one of the three black wires terminated at the switch is probably meant for power downstream somewhere. (should be pig-tailed). Sounds like a switch-loop to me, in which case a open neutral reading would have not much meaning, in my opinion,that is if your test was with the wires that were attached to your fixture. How many cables enter your fixture outlet box? I would use a voltage probe (doesn't require dis-mantling everything) and see where there is voltage present, if any? You may have to dis-mantle all wire nuts, terminations (mark everything if you will forget where wires were joined) and look for 120v source cable and then proceed that way. Hope this helps. others will come along, I'm sure.
 
  #4  
Old 12-12-10, 10:44 AM
Member
Thread Starter
Join Date: May 2010
Location: USA
Posts: 59
I have 121.5 v at the switch and the fixture. I also noticed that 2 hallway light fixtures leading to the laundry room are out. Both are on a 3 way circuit controlled by 2 switches.

I would try the circuit breaker test, but no one can help right now and with 2 flights of stairs between the LR and the panel that could take quite a while.

At least I know I can check the 2 light fixtures and 2 switches.
 
  #5  
Old 12-12-10, 10:56 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,350
Between what two point did you measure the voltage at the switch? Hot to neutral, hot to ground?
 
  #6  
Old 12-12-10, 11:14 AM
Member
Thread Starter
Join Date: May 2010
Location: USA
Posts: 59
Originally Posted by pcboss View Post
Between what two point did you measure the voltage at the switch? Hot to neutral, hot to ground?
I measured hot to ground on the fixture and switch. I get 14.3mv hot to neutral on the switch.
 

Last edited by zich6; 12-12-10 at 12:29 PM.
  #7  
Old 12-13-10, 12:05 PM
Member
Thread Starter
Join Date: May 2010
Location: USA
Posts: 59
Put the meter on the switch, got 121.5 V, then shut off all the breakers one by one. Reading didn't drop. What does that tell us?
 
  #8  
Old 12-13-10, 12:50 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,350
Originally Posted by zich6 View Post
I measured hot to ground on the fixture and switch. I get 14.3mv hot to neutral on the switch.
This could show that the circuit has an open neutral connection. A neutral should not be switched. Was a neutral spliced in the same box as the switch or did you just have a black and a white connected to the switch?
 
  #9  
Old 12-13-10, 12:51 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,350
Originally Posted by zich6 View Post
Put the meter on the switch, got 121.5 V, then shut off all the breakers one by one. Reading didn't drop. What does that tell us?
That would mean that is no way to turn the circuit off. I hope this is not the case. Does this go off if you flip the main to off?
 
  #10  
Old 12-13-10, 01:55 PM
Member
Thread Starter
Join Date: May 2010
Location: USA
Posts: 59
The problem was in a separate switch. Wouldn't you know it was the last thing I checked.

The important thing is that I figured it out before calling an electrician. For over 19 years in owning this house I've finished the basement, including adding 8 circuits, 2 of which were 220 V heaters, along with countless additions and repairs and I've not paid for help once. That, in my opinion, is the true spirit of the DIY'er exemplified on this site. My 19+ year streak is alive. Brett Farve eat your heart out.

Thanks to all that responded and a truly Merry Christmas to all.

Tim
 
  #11  
Old 12-13-10, 06:32 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,212
So...did you find which breaker turns the circuit off?
 
Reply

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


Thread Tools
Search this Thread
Display Modes
'