Half-Hot duplex receptacle no longer hot on top plug

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Old 03-11-17, 01:29 PM
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Half-Hot duplex receptacle no longer hot on top plug

I have a bedroom that has a switch just inside the door that activates the nearest receptacle on the top plug to power on a lamp. It stopped working years ago and despite some help with an electrician friend, the mystery has never been solved. Both the upper and lower plugs on the receptacle are always hot. I replaced both the receptacle and switch with no improvement.

This is a switch loop circuit and the power source is the receptacle. The feed to the receptacle is a two wire and from it to the switch is a 3 wire cable. I noticed the red wire was always hot, which certainly explained why the top plug of the receptacle was always hot. I began looking throughout the entire breakered circuit which is 2 bedrooms, for a shorted red wire but to no avail.

My latest observation is that with the switch and receptacle free of all wires, the red wire is not hot UNTIL I combine the source black wire from the 2 wire cable coming into the receptacle with the black wire of the 3 wire cable that feeds the switch. Once those two wires are joined as is indicated on the diagram on this site, the red wire becomes activated. Further, with the breaker off and all wires separated, a continuity test between the black wire of the 3 wire cable at the receptacle that feeds the switch and that red wire at the receptacle, shows continuity. This tells me there must be a short between the two somewhere in the wall (I think) but that seems so unlikely that I have a hard time buying it. I've tried other wiring configurations that don't involve those two blacks being joined but that does not make the receptacle operate correctly.

The only other thing I've noticed is that whereas this bedroom uses the switched loop 3 wire system, the other bedroom on the same breaker utilizes a 2 wire cable at receptacle and switch but I don't know if that has any bearing at all.

Really stumped here and my friend's suggestion is to run a new "red" wire from the switch going down the wall, through the floor into the basement and back up the other wall to the receptacle but that seems like lot of work that I'm not familiar with and likely is overlooking a more simple answer.

I welcome all suggestions and I thank you.

Rickman60
 
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Old 03-11-17, 01:48 PM
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Is the tab on the brass side of the receptacle broken. It should be. A three wire cable before the 2011 code cycle usually indicates power comes in at the switch so not a switch loop.
 

Last edited by ray2047; 03-14-17 at 09:57 AM.
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Old 03-14-17, 09:32 AM
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Thanks Ray,

Yes, the brass bridge is broken on this replacement receptacle as it was on the old one.

The circuit is from the panel to a string of outlets with the last one being the half hot duplex in question. The source to this receptacle is from the previous outlet, is a 2 wire cable to this box, and the 3 wire cable runs from this box to the switch, which then powers 2 other receptacles. A wiring diagram on this site describes it as a switched loop.

But, never mind all that. How about this observation: I find continuity between the black feed of the 3 wire cable from the receptacle and the red wire from that same 3 wire cable, with ALL wires at both ends of the 3 wire cable disconnected from everything. This tells me there is a short between the two wires somewhere. It also explains why when the source to the outlet is tied to the feed to the switch, the red wire becomes energized which then energizes the top half of the receptacle and nullifies the action of the switch.

Your thoughts on this? And thank you for your reply.
 
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Old 03-14-17, 09:48 AM
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It does happen but it's pretty rare that a cable gets internally shorted.

It would make more sense that the three wire cable makes another stop between the switched receptacle and the switch.

If it was a switch loop it would only be a two wire cable from the receptacle to the switch.
 
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Old 03-14-17, 12:08 PM
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You didn't say how all the wires are connected but it should look something like this:
-white from source to receptacle and white going to switch
-black from source to one receptacle half and black to switch
-red to other half of receptacle

At the switch:
-white from receptacle connected to 2 whites feeding the other receptacles
-black from receptacle to the 2 blacks for other receptacles and to one terminal of the switch
-red from receptacle to the remaining switch terminal
 
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Old 03-14-17, 12:12 PM
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It's possible it was wired incorrectly but now he has the three wire cable disconnected at both ends and measures continuity from the red to black wire. That would indicate a shorted cable.
 
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Old 03-14-17, 12:48 PM
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Yeah,
I was fishing to see if there was an easy way to determine if another box was in between.
 
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Old 03-15-17, 12:54 PM
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Thanks to all. Update, I re-wired with one other suggestion and found the same thing. Top half of receptacle was always hot. Red lead still shorting to black so whether it was a black lead for the top half or the red lead, both were always hot regardless of switch position. I'm not feeling ripping this wall out to find it so I'm going to run a separate and new red from the switch to the outlet by way of floor into open ceiling of basement and back up again and finish it off by wire capping the bad red lead at each end. That should fix the problem and remove any chance for arching between wires since one of the two will then be dead. I really appreciate everyone's input on this and if anyone thinks there's a better fix than what I have proposed here, by all means let me know.
 
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Old 03-15-17, 05:17 PM
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Suggested test

Just for testing purposes, how about disconnecting the 3 conductor cable at both ends and run a temporary 3 conductor cable inside the room, and connect it how you think it should be. Then see if there are any dead receptacles in the area (including the basement). If you don't find one, then you can route a replacement cable permanently.
 
 

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