AC/electric issues with outdoor light wiring.

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  #1  
Old 03-10-15, 01:08 PM
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AC/electric issues with outdoor light wiring.

My friend asked me to come over and see if I could get his outside motion sensor light working. I ended up removing the fixture and he said it was very old and he might replace it. My problem is what caused that fixture to go bad. I checked the voltage at an outlet just to be sure the meter was working right and it read 125 Volts. I then checked to leads to that motion light and it read at different times 187 to 191 volts. It seems to me that is what happened to the fixture. We looked everywhere in that old home and we couldn't find any switch that controlled that fixture, which at one time was a simple outdoor wall light. As I was checking the power lines coming in I noticed that there were two sets, one being the very old type cloth covered and one being a newer type Romex plastic covered. At the breaker box in the basement the same breaker turned off both of those hot wires. That's one thing that puzzles me and another thing is that there was no switch to turn that light off. At the location where the light fixture was mounted there were two/ boxes; one for the fixture and one for a GFI outlet. Both were fed with separate sets of wires, one black and one white. Any ideas what might be the problem or where I might start looking for the problem? Thanks

Rich
 
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  #2  
Old 03-10-15, 03:26 PM
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If it were a "simple outdoor wall light" I'm sure that it had a switch. Can you trace those wires to the next junction box or boxes?
 
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Old 03-10-15, 03:46 PM
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I then checked to leads to that motion light and it read at different times 187 to 191 volts
Sounds like you are using a digital multimeter. An analog multimeter would be more accurate. What does each of the four wires disconnected measured to a known good ground?*

*If no ground in the light box an extension cord with ground plugged in to a known correctly wired grounded receptacle can be used for a ground reference or you can use a wire back to the breaker panel ground bar or neutral bar if no ground bar. Given the age of the one cable it is doubtful even if the newer cable has a ground it is a good ground.
 
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Old 03-10-15, 05:52 PM
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That's exactly what I thought. The light is just outside the kitchen that leads to a small porch. There is a triple gang box as you go outside from the kitchen that has 4 on-off switches (one is a double) and none of them lead up to that box where the light was. I had my friend turn each one off as I checked to bare wires with a volt meter and none of them turned any of the wires off. It seems to me (but I haven't checked it out yet) that the wires to that light go straight down to the main panel, which is in the basement directly under it. But I have no idea where the light, which has been there for about 60 years, gets it's power through a switch.
 
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Old 03-10-15, 08:43 PM
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Did you remove the cover plate from that 4 switch gang box? One of those switches still could be the switch but isn't working properly.
 
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Old 03-10-15, 09:46 PM
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I then checked to leads to that motion light and it read at different times 187 to 191 volts.
Why are you worrying about a switch when obviously It has voltage. The problem may just be the motion light was burned up by excessive voltage if you really have excessive voltage. Try bypassing the motion sensor and see if the light works. If it does measure the voltage with light working.

At this point the switch is just a wild goose that doesn't need to be chased. If it was failing it could cause low voltage but it won't cause high voltage so no reason to worry about its location at this point.
 

Last edited by ray2047; 03-10-15 at 10:06 PM.
  #7  
Old 03-11-15, 01:21 PM
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The problem with that is my friend doesn't want a motion light anymore. He would just like a simple wall mounted light coming off a switch. I could even put in a new switch inside the house but he doesn't want to get too involved with it.
 
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Old 03-11-15, 01:49 PM
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But the main problems need to be addressed first. Does the light work with the motion sensor bypassed and why are you getting higher than expected voltages? Once you have a working light you can try every switch and if none found perhaps that will change your friends mind.
 
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Old 03-11-15, 05:10 PM
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I used my volt meter to/ check if any of the switches worked and none of them broke the power to either of those wires. The only thing we did that shut the power off was to turn off the breaker. That being an old house perhaps means that the first light they had there, which was replaced about 40 years ago, operated on a switch but we couldn't find anything. My pal did tell me that a few years ago (10?) an electrician rewired at least part of the house and maybe they did something off the wall. Maybe he should just put another motion sensor light back on but I still don't know about that high voltage.
 
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Old 03-11-15, 05:56 PM
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Maybe he should just put another motion sensor light back
Or use a wireless switch at a convenient location.
Maybe he should just put another motion sensor light back on but I still don't know about that high voltage.
And if there really is high voltage you may fry the new one. See also post #3.
 
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Old 03-11-15, 06:07 PM
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I wouldn't do just bits & pieces of the job. You have to find that switch & trace the complete circuit. Then you can make decisions.
 
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Old 03-11-15, 07:26 PM
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You have to find that switch
And if it no longer exists how long do you search before you quit? The switch may have been re-purposed for some other load and no longer exist. If you are lucky you might find the two original wires in a switch box no longer connected to a switch (which would make identification difficult) but it could also be the whole connection was moved out of the switch box to some other location. A signal tracer might work but I'm not convinced looking for the switch will serve any purpose. But that's just my opinion.
 
  #13  
Old 03-11-15, 07:31 PM
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Ok, leave the light hot 24/7. Who needs a switch anyway?
 
  #14  
Old 03-11-15, 07:37 PM
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Not saying you don't need a switch. Just adding one would be a lot easier.
 
  #15  
Old 03-11-15, 07:57 PM
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Safe wiring is not something to be learned after the fire trucks have left.
I know what you're saying.

Edit: oops, wrong quote.
 
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