Why Would One Wire Go Live When Another Is Disconnected?

Hey everyone - question about home wiring that was done when the house  was built about 20 years ago (which putting it delicately...is very  shoddy at best).  I'd like to think of myself as fairly knowledgeable in  basic home wiring...but this one has me baffled and I really hope  someone can help.



I am redoing a screened-in porch at the back of our house.  There is  currently a working outlet, and single-pole switch that turns on an  outside bug zapper, and a wire running coming into a second  switch...then leading into nothing in the ceiling (presumably for a  future ceiling fan / light install that was never completed).  I gutted  the entire porch and using one of those audible voltage testers,  discovered the wire than ran into the second switch / ceiling box did  NOT work. 



Not thinking much about it, I tried figuring out how the first switch  (to that outdoor bug zapper) was wired.  Most of the wiring for that  switch and the outlet I mentioned is behind the plywood sheathing of the  house...so it's near impossible to figure out where it goes.  Initially  it LOOKED like the power from the circuit panel came into the outlet  first...and then went out to the bug zapper switch.  (Why did I think  this?  The outlet had a B/W wire coming into it...and another B/W going  out back into the wall somewhere.  Tracing that wire along the basement  foundation best I could...it looked like it went right into the bug  zapper switch).  So wanting to completely eliminate the bug zapper  switch, I disconnected all of the wires that were connected to the  outlet to figure out which set was leading to it.



Here's where I got confused.  When I did this and re-tested voltage at  the outlet, one set of wires was live...and the other set was dead.  And  that makes perfect sense.  Yet the bug zapper switch STILL worked.  OK -  so my conclusion: the power for this bug zapper switch isn't coming  from the outlet.  No problem.  But just because I was near it, I decided  to also check that 2nd switch / ceiling wire combo...and what do you know - it was LIVE!



I got super excited it was working but then super baffled because I  didn't do anything to that ceiling wire at all.  In fact - all I did was  DISconnect 2 sets of wires at a nearby outlet. 



Confused but happy, I was ready to pack it in for the evening and  re-connected the incoming / outgoing wires back to the power outlet.   Flipped the circuit breaker on.  No issues.  BUT - now all of a sudden  the 2nd switch / ceiling wire that magically started working was NO  longer working - just like it hadn't been since I started this whole  process. 



Logic is telling me it's obviously got something to do with the outlet  wiring...since that's the only thing I messed with.  But why would the  ceiling wire all of a sudden become LIVE when the wires going into the  outlet were all disconnected?  It's certainly a first for me.  Can anyone help me figure this mystery out?  Thanks gang!
      


Similar Tutorials

How to Lay Sod - The Right Way!
   - Make sure the green side faces up! And, there are a few more steps if you want to ensure a nice looking lawn. Prepa ...
The Difference Between Volts, Amps, and Watts
   - This article explains the difference between Volts, Amps, and Watts in an easy-to-understand non-scientific way. T ...
Water is Leaking from the Toilet – What do I do? (How to replace the wax seal for a toilet.)
   - If there is water leaking from the toilet, you need to make sure that you know from where the water is leaking. Che ...


Similar Topics From Forums

hello

I am dealing with what seems like a strange issue with a single pole switch, and I am royally baffled even after reaching out to someone a little more knowledgeable than me.



Yesterday: Replaced with a single pole switch with an identical one that I painted (for decor reasons). Two wires were going into the old, and the same 2 wires are attached to the new one. However, the light it controls fails to come on despite light bulb being good, and outlet located 4 feet below the switch fails to operate. With voltmeter in hand I tested voltages.

At the switch: 3 wires feed into it, all whites capped together, and 2 of the 3 blacks (A,B,C) are hot with 110. A is hot and was/is connected to one of the terminals of the single pole switch. B and C (hot) are capped together with a jumper that goes to the other terminal of the single pole switch. So I am royally baffled as to why a switch would be wired with 2 hot wires going into it. I swear it has been like that since we bought the house a year ago, and the light worked fine. I simply replaced the switch with the same wiring, and now it doesnt work. I even touched both hots (A and C) independently to wire B which (using common sense) should be the load wire to the lamp, but the lamp did not come one.



Other outlets in that circuit do not work either. They get 110 to line and ground, but not across the outlet.



I hope I was clear in explaining, and I hope someone can possibly shed some light so I can resolve this.



Thank you
      
Hi,



I would like to wire a switch to be able to cut the power to the ceiling mounted outlets that feed our garage door openers. Running new wiring to them will be a bit cumbersome, so I am hoping to avoid that. The ceiling outlets are powered by light fixtures in the garage (one near by each outlet). There is a 3 wire romex cable running from the light switch to the first light and another one between the lights, and then regular 2 wire romex cables from the light fixtures to the outlets. The red wires in the 3 wire cables to the lights are switchable, the black wires are always hot.



I mainly want to be able to cut the power to the doors when we are away on vacation, and the reason for that is that one night both doors somehow opened up - I have no idea why. I'd hate for that to happen when we're away. Unplugging and plugging in the openers is a bit of a hassle due to the high ceiling.



I thought about wiring in a switched outlet so that I could just reach up with a long handle of some sort and switch off the power to the outlet. It would not be ideal, but definitely easier than getting the ladder out and unplugging the door openers.  However, there is possibly another option that I'd like some input on if anyone cares to comment. I believe I could wire in a switch on the wall next to the light switch that would allow me to cut the power to the black wires in the 3 wire cables. This would cut the power to the ceiling outlets and anything downstream from there (possibly an outside light, I would need to check on that).



My question is, are there any potential issues with this sort of wiring? Is there perhaps any code violation if both hot wires in a 3 wire cable can be switched off separately?



Thoughts?
      
Hello,



I currently have one light switch which operates an outlet in one of my bedrooms.  I want to add a ceiling fan that has independent switches for the fan and light - but I want to make sure i'm wiring it correctly and safely.



Current (First Pic)- Live hot feeds into bottom of switch (bottom insert hole) and the all of the bedroom outlets (pig-tailed) tie into the bottom of the switch on the screw.  Coming out of the top of the switch is one hot which feeds to a single outlet.  All of the neutral and grounds are tied together.



New Plan (Second Pic)- Remove the constant outlet hot from the screw, add a new hot wire to the top of new switch and run a wire up to the attic for fan.  Add another hot wire from the bottom of that switch to the third switch and run another wire up to the attic for the lights.  Re-connect the constant outlet wire to the screw of the last switch.  Connect all the neutrals and all of the grounds together.



At the top of the ceiling, connect the neutrals and grounds together with the fans neutral and ground.  Connect the fan hot to the fan switch hot, and the fan light hot to the light switch hot.
      
Older house with the metal enclosed wiring has stumped me.  I am attempting to add a second switch for a fan off existing light switch in bathroom.  Existing wiring:  W,B,R from panel, W,B to light.  2 white wire are tied together, two black wires to one contact and red to other contact on switch.  Disconnected all wires and confirmed the black is live from panel.  It seems to me the light is seeing power the entire time since the blacks are connected? I'm confused, please help. how do I add another switch onto this circuit?  Thanks!
      
I have 3 bedrooms on 15 amp circuits, 14 gauge wire. Original wiring is one bedroom is on one circuit and the other 2 bedrooms on another circuit. The wall switches in each switched the top half of an outlet in each room. I converted the wire at the wall switch to a 110V feed from the outlet and ran 14/3 from the switch to the ceiling for a ceiling fan. I replaced the outlets since the jumper was cut to isolate the 2 plug ins for switching. Is this whole scenario code compliant?
      
Hello I need seriouse help! In my situation I have a three switch, one for the light, one for the vent fan, and one for the heater. This is in a bathroom rent house. My problem is that when I turn the switch on for the light, the light and fan turn on, when I switch the heater on, that switch does nothing, the same when I switch the fan on. The wall plate is labeled: light, fan, heater. So what I attempted to do is put a switch outlet combo in. I have two black wires, two white wires and a ground. So I put the black wires on brass and the white wires on black,( they are black screws instead of silver, not sure if I got the right kind of switch). So when I did that, when I turn the switch on, the fan turns on, but no light, also when the switch is on the outlet is hot.( which fine that is how I want it). But what did I do wrong, why does fan work but not the light. I my biggest fear is that I might have made a fire hazard. Please help and tell me if what have done is safe, and maybe help me figure out how to turn the fan and light on with the same switch..  Thank you for all your input, have trouble falling asleep, keep thinking the house might burn down.. Sorry for the long post
      
Hi, I have a problem where if I turn off my light switch on one side of the  room, it turns off anything plugged into the electrical outlet on the  other side of the room. For some reason, they originally wired that  outlet on the same circuit as the light switch. I would like to wire the  outlet so that it does not switch off whenever you switch off the light  on the opposite wall.



How do I go about doing that? Thanks.



(p.s. There are just the basic three wires in the electrical outlet; black/white/bare copper ground).
      
I'm trying to fix a problem with a track light installment over the a bar I've just put in. I've done it before. never had issues. but this particular problem is driving me nuts. It just defies logic.  The electrician who actually installed the associated dimmer switches with this dining room area was called as it seems it may be a flaw with his wiring, but he's blown us off and I have to try and solve this myself.



This is how it's all set up. I've been rehabbing our home from top to bottom, and converted our old kitchen into a dining area. Within this dining area are four sets of lights, all controlled from one box containing four dimmer switches. I set up all the new wiring and installation of the lights in the ceiling, and we paid an electrician to come in, check everything out, set up the multiple switches, and connect it all to the board. It's all new copper wiring from beginning to end, as I didn't want to connect or splice in to the old aluminum wiring that was in place. All the new wiring and lights are on a dedicated 15 amp breaker. Three of the sets of lights were set up to be available from the day the electrician came around. The fourth, for the track light over the bar, was left hanging from the ceiling capped off and with the switch off, as I still had work to do installing an overhead wine rack, under which the track was going to be set.



Two days ago I finally got around to putting the track up, but after setting it in place and connecting the power up the lights wouldn't work. I took the lights out to our kitchen, where I installed another track light system some time ago, plugged one of the lights in, and it worked just fine. I then went back to the bar area and used a spare track, then a spare connector, to see if I could isolate the fault, yet neither of the items provided a solution. Now here's the weird bit - every time I tried checking the system out, I'd get 120 volts showing from the wiring and from the track when I'd test with the multimeter. But the second I'd put a light into the track, the multimeter would drop to zero on the voltage reading on either the wiring or the track. Take the light fixture back out, and the voltage would pop back up. Inserting the light was thus completing some kind of odd loop. It wasn't just one light - I double checked by grabbing working lights from the kitchen track and inserting them into the other track - the same problem would pop up. Finally, having come to the conclusion that there was nothing wrong with the track at all, I took the whole assembly over to a nearby wall outlet, used some spare electric cable to connect up to the appropriate slots - presto, the light came on! I even double checked all this by grabbing another light fixture destined for our bathroom, and tried connecting it to the wiring over the bar. Nothing. Yet as with the track light, the minute I took it over to the wall outlet and connected it, the light worked.



So everything logically points to the fact it has to be something to do with this individual circuit, right, because a) the light fixtures work when plugged into another circuit and b) the other three dimmers and lights hooked up in the same box work fine and draw power from the same wire cable/breaker combination. The only things left that I can think of is that the electrician has either wired the dimmer switch up incorrectly or that there's some kind of flaw inside the switch itself. Does this make sense?



A friend also told me to double-check to make sure that the black wire feeding power to the light was indeed the hot wire, and it is.  If I touch it with the black test lead from the multimeter and put the red one to the neutral I show 120 volts. If I keep the black test lead on the black wire and put the red test lead to the ground - I also show 120 volts.



A final point. I know I'm not overloading the circuit - not even close. With all four dimmers maxed and every light on - including the test light on the track - I'd only be drawing 8 amps on a 15 amp breaker, besides which I'm only using one set of lights while I'm working on this problem anyway. This is a dedicated circuit, so there's no additional power being drawn away by something else.



So how am I getting 120 volts from this wiring, according to my multimeter, yet it won't light up ANYTHING and keeps giving off the indication that some kind of loop or short is being created every time I actually plug a light into the track? It's got me totally stumped.



Anyone have any ideas?
      
Well it's not really an outlet but just a junction box that has black, white and bare copper coming out.  I was told by someone before that this would be the end of the line for this circuit since the wires don't go any further from this box.   Its located in my attic just below the eve opening for an attic fan.  I checked the black and white wires a few years ago and measured 115 vac so I installed the attic fan and it was fine until this year.  No fan operation so I check for power and I'm measuring about 3 vac across the white and black wires now.  I disconnected the attic fan and measured the same 3 vac.  Test fan on another power sourch and it works.  Everything else on the circuit seems to be working.  Any ideas what might be happening here.  The attic fan really helps a lot and I'd like to get it working again.  If I need to provide more information please ask and I'll do my best.  Thanks for any help.
      
Greetings!

I'm hoping for some help, I am replacing an old ceiling fan with a new one that has a remote control function.



I discovered in the box on the ceiling there were three wires coming in and capped off with a wire nut.  The previous fan was wired to two other white wires coming in, and the fan is on a switch.



The problem is when I wire the new fan the same way the old one was, it does not have power.



When I wire it to the three capped off wires instead, no power either.



When I wire all of them together (gasp!) It shorts out at the breaker.



Any ideas on how to wire this thing?



Thanks!