Another "hot" neutral problem

[Harleydriver54]

Hi Guys,

This is my first post but I read the entire thread on Mike44's problem with the hot neutral. I am having a similar problem and can't seem to figure it out...especially since it was working fine previously. The background: I installed an outside motion light some time ago and it has been working fine. Recently I installed a backyard flood light and drew power from the motion light for the flood light. I installed a separate switch for the flood light using a "switch leg" to turn it on and off. All of the wires were connected in a junction box. Everything worked fine until this weekend when I needed to remove the switch to allow me to install a pool drain then reinstall the switch.

All I did was 1) disconnect the wires in the junction box to allow me to move the conduit, 2) extend the cable (12-2) coming from the flood light in the old junction box so that it would reach a new junction box on the wall, and 3) reconnect the wires in the new junction box after my drain was completed.

Unfortunately, now neither my flood light nor the motion light are working. To troubleshoot I checked for current and found that every combination was hot, i.e. source to switch leg (black to white), switch leg to flood light (black to black) and source neutral to flood light neutral (white to white). In this configuration I found that the source black AND source white were reading 120V at the junction box. I tried working backwards. I disconnected everything in the junction box AND at the motion sensor (source) and found that the source black was reading 120V and the source neutral was reading 40V. Going backwards further, I found that the outside porch light that I drew my source cable for the motion sensor and ultimately the flood light from is not working, although there is power to the fixture.

I am frustrated given that I it was working before and all I did was disconnect and reconnect the same wires.

Any help would be greatly appreciated.

Thanks in advance.

Mark

[Mike44]

Oooh, geez, sounds exactly like my problem. From the looks of it, you've tried working right back to the start of the run outlet, right? This is what I tried (still haven't fixed it yet as the weather is too cold for the wires outside), but in the fall, I just disconnected everything downstream of outlet and even removed the very first outlet (or in your case, the light I guess?).

So you will have this: Fuse Panel ---> [wire run through wall to junction box] ---> 3 exposed wires in box with nothing attached. Test each wire with your tester: put one probe on the ground wire and the other on the hot (black) and take a reading. Next put a probe on the ground wire and the other on the neutral (white) and take a reading. For me, these read 120V and 0V respectively, indicating that the power feed from the panel was fine and that there is something wrong downstream of this junction box (be it a switch, plug, light, etc.). What are the exact readings for you on these? They should be 120V and 0V. If so, that is good.

Next, try bypassing your first light and sending power directly to the switch; take the voltage readings here as well. And then send this power to your second light. If this works, it could be a wiring issue with your first motion light.

Again, sorry, I'm really not sure as I have not solved mine yet, but I'm just trying to provide something!!! Trust me, I know how frustrating this is!! But hey, just write back with the voltages that you get for both of those configurations so far and we'll go from there!

Good luck!

Mike

[Mike44]

One more thing, I just hope that these kinds of problems are caused by faulty wires within a conduit or anything. Could something like that happen? I'm just throwing this out there because your problem occured after you pulled a new wire through the conduit, right? Same here; the problem started after I pulled new wires through PVC conduit and hooked it up to existing wiring. Could insulation have rubbed off the wire enough that voltage could be leaking across from the hot to the neutral within the conduit run itself? My guess is the fuse would trip though if this happened.....:confused:. Ahh, I don't know.....

Mike

[Harleydriver54]

Mike,

Thanks for your speedy reply. I did measure the voltage going into the motion sensor light, which is where I pulled power from for the switch and flood light. The black was 120V and the white neutral was 40V. I did not measure it back at the porch light because the wires going into the fixture are a black and a switch leg white, so I assumed they would both be 120V.

What I haven't done yet is check the power arriving at the flood light and returning from it via the neutral, I'm not sure if this is relevant but maybe it will reveal something useful. I can check the wires fairly easily because it is only a mere 70 degrees outside!! Haha, just kidding, it sounds very cold wherever you are.

Thanks again.
Mark

[Mike44]

Awww, 70 degrees!! I'm jealous! lol. Hmm, 40V on the neutral - you've got the exact same problem that I've got. If you've got some time to disconnect some wiring, I'd say disconnect the motion light until you've just got the bare wires coming from the fuse panel. Measure those individually. If they measure up fine, connect those wires directly to your flood light (bypassing the motion completely). And then take a new measurement there.

As for much more, I'm not too sure that I can help you further. Again, like I said before, when it gets a little warmer here I'll get outside and see if I can take another look at mine. If I'm able to fix it, I'll definately let you know exactly what the problem was.

If I've got any more ideas, I'll post back!!

Mike

[DE_Mikey]

I'd like to help, I'm always up for a challenge.

In your second post you mention that you are feeding the motion sensor from your porch light, and that your porch light has no neutral, just a switch leg. A switch leg is just that, a leg to switch the line wire. In the "fixture" there must be a line and a neutral. I'm not sure what you are describing is a switch leg.

Where is the neutral wire for your motion detector comming from?

Keep in mind that even when properly wired, there is the possibility that you can see an ac voltage on the neutral wire at the detector. The detector, once wired, will continuosly consume a small amount of current which may be read by a meter to ground.

I look forward to your reply or resolution.

Mikey

[Mike44]

Hey Harley, I posted an update about this problem on my thread (http://www.construction-resource.com/forum/showthread.php?t=6490 - post #11). Take a look at it - I had a conversation with an electrician and that is what he told me. I think we both have a faulty neutral somewhere along the line. But anyways, take a quick read (or well, actually it's quite long, but still some good info in there!!).

Mike

[Mike44]

Were you able to solve your problem at all? If not, post a diagram of your wiring. I only say this becuase I think I've figured out my problem (fingers crossed)! I would just like to take a look at your switch leg wiring though.

Mike