HELP: Existing Switch Loop

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Old 01-05-18, 07:44 AM
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Question HELP: Existing Switch Loop

I am attempting to install a replacement light fixture in our utility room and it appears the existing box is wired into a switch loop. A little summary:
  • The original light fixture was one bulb, I am replacing with a two bulb fixture
  • There is one red and four wire bundles (black, white, and ground) coming in to the box (see attached image)
    • One bundle is directly from the switch
    • One bundle is directly from the power source
    • Two bundles go to other lights, outlets, and smoke detectors
  • Switch is wired with BLACK on top and WHITE on bottom

Now I have tried a few combinations that seem to fail in one way or another.
  1. (Switch White to Black Source) + (Switch Black to Light Black) + (Light White to White source and outgoing white)
    • No light
  2. (Switch White to Black Source) + (Switch Black to Light White) + (Light Black to ALL white)
    • No light
  3. (All White to Light White) + (Switch Black to ALL Black)
    • Light but no effect by switch (duh!)
There was one other combination, I didn't write down, that caused the switch to function, but would trip the box if I tried to shut it off.

I would greatly appreciate any help I can receive on this and will post any other info that is needed. Thank you all.
 
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Old 01-05-18, 09:36 AM
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I don't know what the red wire is for. Pictures or a more detailed description is needed.

(Switch White to Black Source) + (Switch Black to Light Black) + (Light White to White source and outgoing white)
No light
Your above quote should work, the description is correct.

Source hot (black) goes to switch white (loop) and down stream lights and receptacles.
Source neutral goes directly to the light and down stream lights and receptacles.
Black from switch goes to the light black(s) only and does not connect to anything else.

Red to be determined.
 
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Old 01-05-18, 09:38 AM
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Did you open all the wiring connections in the box ??

The red could possibly be from the smoke detector circuit.
DO NOT randomly connect that wire.
 
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Old 01-05-18, 09:51 AM
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Don't take offense, but are you sure you have two good light bulbs in your fixture? I was pulling my hair out after installing a couple outdoor fixtures because they weren't working, and the issue turned out being I was unknowingly using 12Vdc bulbs. They kept burning out as soon as I flipped the switch, but didn't realize what was going on because I couldn't see the bulbs burning out (because the switch is inside and fixtures are outside out of view)

Does the outlet have power?

Could be a bad switch. I have encountered that before. You can temporarily short the white and black inside the switch box to bypass it (e.g. use a spare piece of insulated wire to short the two screws).
 
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Old 01-05-18, 02:08 PM
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Originally Posted by Handyone View Post
I don't know what the red wire is for. Pictures or a more detailed description is needed.



Your above quote should work, the description is correct.

Source hot (black) goes to switch white (loop) and down stream lights and receptacles.
Source neutral goes directly to the light and down stream lights and receptacles.
Black from switch goes to the light black(s) only and does not connect to anything else.

Red to be determined.
Hello Handyone, thanks for the reply. The red was capped and I left it as such. I know what you are saying, I keep scratching my head on why this set-up failed. Let me make sure I Understand your description fully:
  • BLACK SOURCE :: SWITCH WHITE + OUTGOING BLACK
  • SOURCE WHITE :: LIGHT WHITE + OUTGOING WHITE
  • SWITCH BLACK :: LIGHT BLACK
I will try this set-up, I am pretty sure I did once before, but it has been a lot of combinations. I will keep you posted
 
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Old 01-05-18, 02:12 PM
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Originally Posted by mossman View Post
Don't take offense, but are you sure you have two good light bulbs in your fixture? I was pulling my hair out after installing a couple outdoor fixtures because they weren't working, and the issue turned out being I was unknowingly using 12Vdc bulbs. They kept burning out as soon as I flipped the switch, but didn't realize what was going on because I couldn't see the bulbs burning out (because the switch is inside and fixtures are outside out of view)

Does the outlet have power?

Could be a bad switch. I have encountered that before. You can temporarily short the white and black inside the switch box to bypass it (e.g. use a spare piece of insulated wire to short the two screws).
I am able to successfully get the lights to light by bypassing the switch, so the bulbs are good. I have tried two switches as well to rule out the switch, but they are used ones I had in my shop. Maybe I'll pick up a new one to make sure.

Originally Posted by PJmax View Post
Did you open all the wiring connections in the box ??

The red could possibly be from the smoke detector circuit.
DO NOT randomly connect that wire.
Red was capped alone and I kept it capped.
 
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Old 01-06-18, 10:56 AM
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Thumbs up Thanks

Thank you all, I picked up a brand new switch and re-wired as I had before and everything works fine now. An added bonus, my wife is done saying "I told you so"
 
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Old 01-06-18, 01:34 PM
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Oh no...... you aren't the type that puts old switches in the electrical bin for future spares.
 
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