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We are trying to replace our original toggle switch in the kitchen of our manufactured home to a dimmer switch. The original switch had a self-contained box with three bundles of wire feeding in. Each bundle has a white, black and ground (9 wires total). Two bundles come from the ceiling and one bundle comes from the floor. One of the two bundles coming from the ceiling has red marking on it. We feel this is the switch loop starter location to the rest of the lights on this side of the house.

We put in an old work box since we did not have a box for this switch. We have a dimmer switch with three screws and one ground. Two of the screws are brass and one is copper. We wired all three grounds together with the ground from the switch. We wired all three white together and used a jumper to wire to the brass screw on the bottom of the switch (opposite side of the copper screw). We wired all three black wires together and used a jumper to wire to the copper screw on the other side of the switch. We have one brass screw with nothing attached.

The switch does not function when we turn the breaker on. When we turn the breaker on, the kitchen light will stay on. Turning the switch off in the kitchen does nothing to cut the light off. The rest of the lights on that side of the house work correctly (turning off and on) when we have the breaker on. We need to to figure out what we did wrong. How do we wire this switch so we can cut the light off in the kitchen while keeping power on the loop to the rest of the house?

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  • Three screws plus ground on the new switch means it's a 3-way switch. Is this a 3-way circuit (i.e. there's another switch somewhere that controls the same light(s)? If it's a 3-way, you have to be very specific in how it's wired.
    – FreeMan
    Oct 2, 2023 at 18:37

1 Answer 1

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Next time, take a picture of the wiring before disconnecting the old switch. Then you just wire up new to match old.

Since you don't know how the wires were connected previously, you need to figure out where the wires in each cable go. A typical setup is:

  • One cable bringing in always hot and neutral.
  • One cable taking switched hot and neutral to the switched light.
  • One cable taking always hot and neutral to another receptacle or switch.

A switch loop is a possibility, but if that's the case then typically it would be the only cable in the box. 3 cables can be a switch loop plus two cables not related to the switch and light, but that is less likely.

  • Carefully separate all the wires except the ground wires.
  • Turn on the breaker.
  • Use a non-contact voltage tester (NCVT) like this Klein from Amazon:

NCVT-1 Klein

and determine which wire is hot. It should be the black wire in one of the cables.

  • Mark that cable as "incoming power".
  • Turn off the breaker.
  • Connect the black wire from this cable to the black wire in one of the other cables and connect the white wire from this cable to the white wire in that cable.
  • Turn on the breaker.
  • See if the kitchen light is on and/or the other lights are on. It should be one but not the other. Mark the second cable accordingly "kitchen light" or "outgoing power"
  • Turn off the breaker.
  • Mark the last cable as either "kitchen light" or "outgoing power".
  • Connect all the white wires together.
  • Connect the black wire of "incoming power", the black wire of "outgoing power" and a short additional piece of black wire (14 AWG or 12 AWG if this is a 15A circuit, 12 AWG if this is a 20A circuit) together.
  • Connect the other end of the short wire to the "line" or "hot" or "incoming" screw on the dimmer. Some dimmers will have two such screws that can be used interchangeable, some must have incoming power to a specific screw - check the instructions.
  • If the dimmer requires neutral, add a short additional piece of white wire (14 AWG or 12 AWG if this is a 15A circuit, 12 AWG if this is a 20A circuit) to the bundle of white wires and connect the other end to the "neutral" connection on the dimmer - check the instructions.
  • Connect the "kitchen light" black wire to the "load" or "switched hot" or "outgoing" screw on the dimmer. Again, there may be two such screws for line/load that are interchangeable or it may have a specific configuration required - check the instructions.
  • Turn on the breaker and test the dimmer.

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