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Old 02-15-2012, 06:48 AM   #1
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Power loss when load applied???


I have a weird situation that I can't figure out...Inside the garage there is a three way switch that powers the outside light. When testing without any load (wires exposed, light isn't connected), the switch seems to work properly; however, when I connect a motion sensing security light, power is lost and the switch doesn't seem to work...any ideas?

Thanks!

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Old 02-15-2012, 06:50 AM   #2
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Power loss when load applied???


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Originally Posted by eugenefks
I have a weird situation that I can't figure out...Inside the garage there is a three way switch that powers the outside light. When testing without any load (wires exposed, light isn't connected), the switch seems to work properly; however, when I connect a motion sensing security light, power is lost and the switch doesn't seem to work...any ideas?

Thanks!
Faulty motion sensor?

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Old 02-15-2012, 06:51 AM   #3
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Power loss when load applied???


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Faulty motion sensor?
Brand new unit. Installed elsewhere and works fine.
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Old 02-15-2012, 06:51 AM   #4
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Power loss when load applied???


What do you mean when you say power is lost?
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Old 02-15-2012, 06:53 AM   #5
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Power loss when load applied???


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What do you mean when you say power is lost?
current* (using tester)
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Old 02-15-2012, 06:54 AM   #6
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Power loss when load applied???


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current* (using tester)
What??
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Old 02-15-2012, 06:58 AM   #7
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Power loss when load applied???


It appears you've tested the switch and tested the light. You say both work. Have you tested the circuit for the presence of voltage?
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Old 02-15-2012, 07:13 AM   #8
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Power loss when load applied???


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It appears you've tested the switch and tested the light. You say both work. Have you tested the circuit for the presence of voltage?
I tested the circuit (at the light location) using non contact current tester...I'll check for voltage with a multimeter today, but if voltage is good any other ideas what it could be?
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Old 02-15-2012, 07:21 AM   #9
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Power loss when load applied???


Bad bulb?
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Old 02-15-2012, 07:35 AM   #10
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Power loss when load applied???


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Bad bulb?
no...
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Old 02-15-2012, 07:50 AM   #11
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Power loss when load applied???


Do you have a neutral at your light location to power the motion detector?

It would be a wirenutted unused wire in your box.

Last edited by zappa; 02-15-2012 at 07:53 AM.
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Old 02-15-2012, 07:51 AM   #12
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Power loss when load applied???


Does a different (perhaps non-motion sensing) light work in the circuit?

A severe voltage drop when you try to use something (you apply a load) usually means a loose connection somewhere upstream.

Voltage staying the same but the light or other equipment does not work usually means a problem downstream of where you are testing.

Do not measure the voltage across two switch terminals. Although there are some uses for this, this does not produce useful results here. Measure voltage from neutral to each desired point of interest.
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Last edited by AllanJ; 02-15-2012 at 08:02 AM.
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Old 02-15-2012, 08:05 AM   #13
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Power loss when load applied???


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Originally Posted by eugenefks

I tested the circuit (at the light location) using non contact current tester
Clamp style? And it showed current flow?
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Old 02-15-2012, 08:13 AM   #14
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Power loss when load applied???


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Do you have a neutral at your light location to power the motion detector?

It would be a wirenutted unused wire in your box.
Well the wires are old with fabric/asbestos wrapping which is all faded now, but when testing only one was hot. I'm assuming the other was neutral?

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Originally Posted by AllanJ View Post
Does a different (perhaps non-motion sensing) light work in the circuit?

A severe voltage drop when you try to use something (you apply a load) usually means a loose connection somewhere upstream.

Voltage staying the same but the light or other equipment does not work usually means a problem downstream of where you are testing.

Do not measure the voltage across two switch terminals. Although there are some uses for this, this does not produce useful results here. Measure voltage from neutral to each desired point of interest.
Thank you!
You recommend checking connections at the switch box? Maybe changing the switch? If that doesn't work - I may just run a separate line all together only for this light, but this is my last reserve.
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Old 02-15-2012, 08:25 AM   #15
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Power loss when load applied???


Nevermind...I'm not sure where my head is this morning.
You should have a neutral up there.

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Last edited by zappa; 02-15-2012 at 08:36 AM.
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