The lighting circuit in my garage has a switch loop, to shut the lights off. The lights are pull-chain florescent lights. The switch is off; the light in the switch is bright. When the switch is still off, and I pull the pull chains on both the lights, (shut them off) the light goes dim, but power is not to them. Seems the switch might be bad, because there is a slight voltage on the top screw. Weird...Is this normal? The outlets test ok ....

First pic - Lights off, pullchains switched on.
Second Pic - Lights off, pullchains switched off.
Third Pic - Lights on, pullchains on.
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Your switch may need a neutral for proper operation. An older switch loop does not have a neutral.

With the pull chain off no voltage can trickle through the ballast.

You box should be grounded. How are you measuring voltage? Between what two points?

 

Nah, the neon style basically just connect the bulb in parallel with the switch contacts. When the switch is off, a small amount of power 'leaks' through the fixture to create a complete circuit, and when the switch is on, the bulb contacts are shorted, which makes the bulb go out. I've never seen one of that style that requires a neutral.

It's actually similar in function to the automotive fuses that light up when they blow. When the fuse is intact, the bulb is shorted, but if the fuse blows, a limited amount of power backfeeds though the load and lights the bulb.

 

cool, i guess ok then..............

 

my friend is the one who checked it, and i think he said something like 40v was coming through. Top post on switch i think.

 

There should be no actual potential on the switch yoke. 40V might be an induced reading.

Did your friend use a digital meter or an analog meter? What was the other probe touching?

 

With the neon bulb in there you will have current flow with the swtich off because the bulb is in parallel with the switch.