Strangely eerie, dim shop lights - hopefully not supernatural causes

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Old 07-22-13, 09:53 PM
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Strangely eerie, dim shop lights - hopefully not supernatural causes

Hope someone can help - I'm baffled.

I've had incandescent lights in my shop that worked fine for 8 years, then the other night I walked into the shop with my wife, she hit the lights and they glowed at about 25% of their brightness.

She says, "Creepy." I say, "Sexy."

No, actually I got pretty mad. I wired it myself so something's up.

Now the lights sometimes come on, usually don't, and every once in a while do the strange dimmy thing.

Here's the setup:

Main comes in directly from the meter to a service panel in the shop (had a pro do that part).

2 breakers: Breaker #1 services 6 outlets (just light woodworking - no welding), and breaker #2 services interior and exterior lights.

All outlets on breaker #1 are working fine and test at full voltage.

The problem is with breaker #2. This run goes like this: The wire goes from the breaker to a switch box (for 4 interior shop lights), where (before the switch) it splits to service another switch for 2 outside coach lights.

In testing with a multimeter, I found that the line coming IN to the first switch box is reading full voltage, but as soon as I touch the two incoming wires to the wires for either the interior or exterior lights, I completely lose the voltage reading on the multimeter - even though I'm testing the incoming wires that just seconds before tested with perfect voltage!

Basically, as soon as I touch the good wires to another set, it kills the circuit.

The only thing I can think of is that I ran 4 incandescent lights in series, using bare bulb fixtures, and on these, they don't have any spot to attach the ground wire. So on the 4th light, I twisted the ground around the metal bracket for the overhead garage door since it was a few inches away (although this is NOT the case with the other run that connects to the coach lights outside and DO have grounding in the fixtures)... and these aren't working wither!

An ideas? THANKS!
 
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Old 07-23-13, 01:58 AM
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Welcome to the forums.

Your lights don't require a ground to work properly.

Your four light fixtures are in a row and are connected in parallel....... not series.

Leave the lights connected to the circuit while you are testing. You have a connection that is not fully making and the lights are loading the voltage down. Now start from the beginning of the circuit......right at the breaker to see where you lose the voltage.
 
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Old 07-23-13, 02:50 AM
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I'll bet you are using a digital multimeter. If so you are seeing induced voltage not true voltage. That is why we usually recommend an analog multimeter. The lower impedance will bleed of the induced voltage and give you a truer reading. I know I'm not helping you with your problem but I thought you should know the reason why the voltage looks okay with no load.
 
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Old 07-23-13, 07:41 AM
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Do the light work properly if you remove the switch and splice the two wires together? I am suspecting a bad switch.

Also you cannot measure voltage between the two screws on the switch. You need a ground reference.
 
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Old 07-23-13, 08:57 AM
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If all the lights on that circuit are dimming I would start at the panel. It's possible you have corrosion or loose connection. Check where the breaker clips into the panel's power bar, where the wire attaches to the breaker and where the neutral wire is screwed to the neutral buss. If everything seems tight and clean there I would look at the first light in the string. Also inspect the switch and connections to it. If all are dimming I suspect that it is somewhere at the head of the wiring run. If you did in fact wire your lights in series (I hope not) then #1 the wiring is incorrect and needs to be repaired and #2 the weak connection could be anywhere.
 
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Old 07-23-13, 11:17 AM
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You can plug a 3-conductor extension cord into any of the grounded duplex receptacles in your shop and use the slots in the female end as reference contacts for testing in your switch box.
 
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Old 07-23-13, 06:50 PM
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Thanks for the help!!!

Yes - I'm bypassing the switch and just connecting the wires, and as soon as I connect the incoming wires to the circuit with the lights on it (either one) the voltage on the multimeter drops to nothing - and I'm using an analog one. No needle movement at all.

So - if I test along the circuit of the 4 lights, I might get a reading even though I don't get a reading at the beginning?
 
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Old 07-23-13, 06:57 PM
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The ceramic bulb holders have two gold screw and two silver screws on each. So I fed the black wires to the gold screws and the white wires to the silver screws, chaining each one along - is this correct?
 
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Old 07-23-13, 07:42 PM
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I'm bypassing the switch and just connecting the wires, and as soon as I connect the incoming wires to the circuit with the lights on it (either one) the voltage on the multimeter drops to nothing - and I'm using an analog one. No needle movement at all.
This is as it should be. Do you see 120V when the wires are disconnected?

So -
if I test along the circuit of the 4 lights, I might get a reading even though I don't get a reading at the beginning?
You should see 120V, hot-to-neutral, at each point in the circuit, on the pair coming from the panel - both before and after the switch.

The ceramic bulb holders have two gold screw and two silver screws on each. So I fed the black wires to the gold screws and the white wires to the silver screws, chaining each one along - is this correct?
That should work. However, many of us prefer to splice each color to a pigtail of the same size and color and connect that to the fixture, so that a failure in one of the fixture connections can't interrupt the continuity of the circuit.
 
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