First off I know the switch the works I plugged it into a different circuit where I have another one and the pilot light turned on when the switch was on. However when I have it installed in the problem circuit the indicator light is switched and is illuminated when the light is off instead of it being illuminated when the light is on.

The circuit is for the downstairs lights in an older building so I am thinking it has to be something with how the lights are wired. The switch works the lights just fine so I am figuring it is something to do with the neutral side. I am unfamiliar with this light switch and how it works internally.

What would make the light come on one way in one circuit and opposite in another? I am unsure the exact brand I am an amateur electrician just helping a friend, but it is similar to the Leviton 15 Amp Combination Switch with 25-Watt Neon Pilot Light found on the home depot website. any help or ideas would be greatly appreciated

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    Can you provide us with photos of this switch? – ThreePhaseEel Jun 18 '16 at 19:43
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    We're not mind readers: you have to show us the wiring diagrams and the voltage measurements on the wires when the switch is not connected. Among other things, is the "problem" circuit a 2-switch setup? – Carl Witthoft Jun 18 '16 at 20:04
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    A two-terminal switch (which just opens and closes) which has a pilot light cannot light the light when the switch is on, as the two terminals will be shorted together and there will be no voltage. Such switches naturally light when they are turned off. There are three-terminal switches which behave otherwise. (Which do you have?) – Daniel Griscom Jun 18 '16 at 20:38
  • @DanielGriscom did you even bother to look at the description of the referenced switch? – Carl Witthoft Jun 19 '16 at 12:39

With pilot switches, you can get any combination you want, simply by wiring it differently.

enter image description here

  • Top: the pilot is on when the switch/light is on.

  • Middle: The pilot is on always.

  • Bottom: The pilot is on when the switch/light is off. However, this works by leaking power through the bulb. So it only works if the bulb is not burned out, and is able to tolerate this leakage (incandescents can for sure.)

In these drawings, ground is omitted for clarity, neutral is white, always-hot is black, and switched-hot is red for clarity. The internal arrangement of the pilot switch is shown, so you can see why it works.

Note also the "upper right terminal" in my drawings. See how it serves both the switch and the light. In some pilot switches, this actually comes out to two screws on the side of the pilot switch with this side considered "common". In that case, the "sides" on your switch won't be in the same places, not that they ever are.

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