In the entry way of my 1935 home, there is a double switch box. One switch is a basic,two wire light switch controlling the indoor entry light. The other switch is a mechanical Intermatic EJ351 timer switch controlling the porch light. Each switch uses only two wires.

Coming from the conduit attached to the box are three cloth covered wires. They are old and very dirty, but, appear to be in good condition. The colors don't make sense to me. One appears to be red, one green and one black. Using a meter set at 200 VAC, I put the black probe to the junction box (as ground) and tested each wire with the red probe. The black and red wires showed no voltage, but, the green wire has full line voltage. The black wire is connected to the simple light switch, the red wire is connected to the mechanical timer and the green wire is connected to both. My limited knowledge of house wiring thereby suggests that the red and black wires are both neutral and the green is "hot". Not withstanding the colors, I would have thought there would be two hot, one neutral and a ground wire. At least the box appears to be a good ground.

The question is, how do I wire the Smart Switch KS-602 or can I even use it? It requires four wire connections which they label load, line, ground and neutral. I assume ground I can connect to the box, the red to the neutral, the green to line, but, what do I connect to load, another neutral?

Thank you for any help.


  • 2
    We're going to need some closeup pictures of the opened switch box and switches. Don't disconnect anything.
    – JACK
    Oct 24, 2020 at 23:08
  • 1
    Can you post a photo looking into the back of the switch box please? Oct 24, 2020 at 23:51
  • There'd be no reason for neutrals to come to a switch box. Switches don't need neutral... at least, they didn't when they were human powered... Oct 25, 2020 at 1:58
  • 1
    Gosund can't be used anyway. In the US you are required to use equipment that's been approved by a competent testing lab such as UL, and Gosund is cheaply built and cannot pass those tests. That means it is not safe to use. Oct 25, 2020 at 2:21
  • What functionality do you want out of a smart-switch at this location? Oct 25, 2020 at 14:55

1 Answer 1


From your description, it sounds like the green wire is live, the black wire is connected to the entry light and the red wire is connected to the patio light. There is no ground or neutral coming to the box. The EJ351 timer switch is specifically advertised as not requiring a neutral connection.

Try turning on either light and then measuring the voltage on the black/red wires. These wires will now "appear" to be hot wires since they will be connected to live through the switch. When the lights are off the wires will "appear" as neutral since there is a (relatively) low-resistance path to neutral through the lights. They are the switched hot wires going to either light.

You cannot use your smart switch without a neutral wire.

  • Yes, if I turn on either light, I measure line voltage on the black or red wires. I understand I need a neutral wire to use the Smart Switch. What I don't understand is, if the black and red wires are not hot and they are not neutral, what are they?
    – Allan
    Oct 29, 2020 at 19:26
  • 1
    @Allan Switched hot. Oct 29, 2020 at 22:11

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