Not Understanding this Wiring

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  #1  
Old 07-17-15, 04:09 PM
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Not Understanding this Wiring

Hello everyone,

I am replacing two switches and noticed that one is a single pole switch and that the other is a three way switch. I was able to replace single pole switch with no problem and I can do the same with the three way switch but what is bothering me is that I am not understanding why the wiring is set up the way it is. It seems rather cluttered for just two switches. The switch on the right is the single pole switch I have replaced and the switch on the right is the three way switch I have yet to replace. The wire from the top terminal of the single pole switch connects to the bottom right terminal of the three way switch. It may be hard to see in the picture, but there is another wire connected into the hole next to that terminal.


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  #2  
Old 07-17-15, 05:02 PM
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What light does the 3 way switch control? Where is the second 3 way switch? It could be that the wire between the two switches, in that box is just a jumper. To be sure, you need to test the juice, in both switch boxes.
 
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Old 07-17-15, 05:36 PM
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The wire from the top terminal of the single pole switch connects to the bottom right terminal of the three way switch.
Switches really don't have a top or bottom so that is not useful when discussing switches. You could argue the SPST switch should be put in a certain way so the on/off reads correctly but the terminals are interchangeable so it doesn't matter which terminal a wire is on.

3-ways the common terminal does matter but its location can vary with the manufacture so again top is not meaningful. What is meaningful is which is the common, the odd colored screw (usually dark gray). Does the jumper connect the common terminal of the 3-way to the SPST switch?

Other things not related directly but you should not have two wires on one screw. They aren't rated for that. The back stabs are less reliable and use should be avoided. If you have two wires use a pigtail.

Answer mine an Pulpo's questions and we will go from there.

Final point Pulpo suggested:
you need to test the juice, in both switch boxes.
Just remember that can NOT be done with a non contact tester.
 
  #4  
Old 07-17-15, 05:50 PM
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I actually don't know what the 3 way switch controls. I thought it turned on an exterior light fixture on the other side of the wall but it isn't turning on and I wouldn't see the point of a 3 way switch for that light especially since I can't find the other 3 way switch as weird as that sounds. This is my friend's house and I told him I would help him with this but he doesn't seem to be really sure about it either.

The screws on all three terminals have rusted so I can't tell for sure which terminal is the common. It does seem though that the wire running from the SP switch to the 3 way switch is a jumper but I do not know that for sure. I will reinspect it and try to take better photographs.
 
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Old 07-17-15, 06:10 PM
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I would reconnect the SPST and disconnect the 3-way (remove the jumper and cap the other wires after diagramming the connections).. If nothing fails to work when you do that I'd just leave it disconnected. If something does no longer work we can go from there.

Go ahead though and post more pictures. We might see something.

Do you know why the screws are rusted.
 
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Old 07-17-15, 06:21 PM
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We don't need better photographs. We need the answers to the questions that we asked. Here's how to trace it. Disconnect what we think is the jumper between the single pole & the 3 way switches. Test which wire is the actual hot lead that feeds that box. Mark it with a piece of tape. Notice which switch it goes to first.

Then find the circuit breaker that controls that switch box & shut it. Walk around the house & make a note of what else it controls. You may have to open a bunch of switch boxes to determine what else the breaker controls but you will find the other 3 way. When you find it, let us know.
 
  #7  
Old 07-22-15, 07:18 PM
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I removed the three way switch and on the back it had the word common embossed into the plastic with an arrow pointing to the terminal. It is in fact the terminal that has the jumper wire attached to it and the other wire. I replaced it with a new 3 way switch and then changed the light bulb to the exterior light fixture and it to my surprise actually controls that fixture. What I don't understand is why did a 3 way switch have to be used to accomplish that. Couldn't a single pole switch have been used? Couldn't the jumper and the other wire be put together in a wire nut along with another jumper to the terminal so that only one wire is on the terminal and then the fixture wire could go to the other terminal?
 
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Old 07-22-15, 07:33 PM
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What I don't understand is why did a 3 way switch have to be used to accomplish that.
There either is or was a matching three way switch. If you can't find its mate...... it may have been disconnected or covered up now.
 
  #9  
Old 07-23-15, 02:17 AM
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Where is the exterior light? Is it near the front entrance, another entrance or the garage? Is the garage attached to the house? If the garage is attached, are there some switches, in there that you haven't checked?
 
  #10  
Old 08-06-15, 10:04 PM
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The exterior light is next to a side entry door to the house. The garage is unattached but does have a 3 way switch which is paired with a different switch for different fixtures. I ended up replacing it with a single pole switch.
 
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