I am replacing a light switch with one including a neon indicator. There is only one cable to the switch but the new switch has live and neutral terminals for both 'in' and 'out'. Which terminals do I use?

  • So the switch has 4 screws on it? Do you have a picture or a model number? – JPhi1618 Mar 26 '19 at 19:17
  • If it's both in and out it could be an inverter 3-way system (US 4-way) – DDS Mar 27 '19 at 11:26

you can use this kind of connection (called switch-finder) with neon light connected in parallel to the switch: neon is on when fixture is off, neon is off when fixture is on.

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You use Live In (supply) and Live Out (load).

The neon will not work, unless you also have a neutral present at the switch.

  • 2
    There are switches with pilot lights that work with no neutral. – JPhi1618 Mar 26 '19 at 19:17
  • 1
    Yes these use a tiny current through the load to illuminate when the contacts are open, this is why LED's glow with most lighted switches. – Ed Beal Mar 26 '19 at 21:02

You'll need to call an electrician to change the cable between lamp and switch.

In this installation, power comes into the lamp, rather than the switch. There's nothing wrong with that, but the wiring in this house is older and does not conform to NEC 2011. As such, there is no neutral (return) wire in the switch box.

Without a neutral wire, it is not easy to power anything in the switch box that needs power. Normal switches do not.

What your switch actually has is

  • For the switch: line (always-hot) and load (switched-hot).
  • For the indicator: supply (switched-hot) and neutral.

On some switches, two of those terminals are wired to be common, but can be separated.

If you want the pilot on when the switch is off, there's a chance of doing this without rewiring. Check your switch and lamp to see if it supports this, but the pilot can be wired to be in series with the lamp., so it lights when the switch is off.

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