Bathroom Lighting Fixture - Electrical Issues

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Old 07-20-13, 12:05 PM
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Bathroom Lighting Fixture - Electrical Issues

Help - having a problem installing new bathroom lighting fixtures. I'm a reasonably capable guy but not an expert on wiring or electrical. It's my first time to replace bathroom lighting.

I'm working on the kids' bathroom which has two light fixtures controlled by a single switch. I removed and discarded two 25-year old light fixtures. The wiring out of the wall looks like the following pics. For fixture 1 wiring, the blue labeled wires are the hot; the other side come from the switch.

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So I then followed other instructions here on doityourself. For fixture 1, I connected the hot black to the switch white. I connected the switch black to the fixture black and the hot white to the fixture white. I connected all three grounds to each other, and then mounted the light fixture. For fixture 2, it is much more straightforward, of course. I connected the fixture black to the other black and the fixture white to the other white, and the grounds to each other. Then I installed fixture 2.

What happened when I turned on the power was strange. Five of the six bulbs in the two fixtures turned on extremely dim. The sixth didn't light at all.

I immediately checked the bulbs in another socket and they all worked fine, to the proper brightness.

I then unmounted fixture 1 and checked all the connections, which seemed to be fine.

So what did I do wrong? It can't be an internal wiring issue because the old lights were working just fine before I threw them away. Is there a grounding issue or a sneak circuit somewhere?

Any help or advice is appreciated.
 
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Old 07-20-13, 12:08 PM
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Welcome to the forums! The wiring you have tells me the blue coded black wire is hot only when the switch is turned on. Confirm that. If that is the case you will connect the blacks and whites of the box and light and make it a day. I doubt the other cable is a switch loop, as you suspect.
 
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Old 07-20-13, 12:13 PM
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You are right. I didn't need to turn off the circuit breaker to make the "hot" wire go cold. I just turned off the wall switch. So, to reconfirm, all I need to do is:

Connect both incoming black wires to the black wire on the fixture
Connect both incoming white wires to the white wire on the fixture
Connect all three grounding wires together

Correct?
 
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Old 07-20-13, 12:19 PM
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You have too many wires on the pancake box at fixture 1. You need another style of box with more capacity.

There is no ground screw in either pancake box, nor are there any cable connectors in use. Both boxes need ground screws and cable connectors to be installed.
 
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Old 07-20-13, 12:30 PM
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Nice question. I had to use the 1/2" pancake box because there are 2x4s behind the sheetrock. No space between studs for a traditional box.

As for ground screws, my picture does not show the rotating plate that mounts to the pancake box, which has a ground screw. I also did use standard wire connectors (see below) so rest assured about that.

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As for grounding, are you saying that I should always ground to the screws on the box, and not just attached the fixture ground to the power grounds?
 

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Old 07-20-13, 12:59 PM
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Technically, yes, since the yoke can become loosened, they both need to be grounded. Jim is referring to the strain reliefs necessary where the cable comes through the boxes. You will have to chisel out the 2x4 deeper and install a 2" deep box on that stud, since you have two cables. I missed that, being concerned primarily with your connection problem.

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Old 07-20-13, 01:00 PM
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The ground needs to be bonded to the box as well as any fixture wires or brackets.

These are what you need on the cables.

https://www.google.com/search?q=cabl...w=1517&bih=714

You need a box with a sidecar with the additional space. Something like this.

Fan And Fixture Boxes | Deepest L-Shaped Fan and Fixture Mounting Box
 
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Old 07-20-13, 01:02 PM
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Jim types faster than me today for some reason. Yes, rather than chiseling, I forgot about the side car boxes. Use them all the time for ceiling mounted pendants, knowing full well where the client wants them is directly under a joist.
 
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