4 Way Switch - Last Box Missing Neutral

I am in the process of replacing my hallway 4-way switch with GE Z-Wave switches. I have discovered that one of the boxes (seem to be the last in the line) does not have a neutral wire. Here is what I have

Box A - primary - has four wires (two blacks, one red, one white) plus ground. I installed the primary switch there. The blue LED lit up.

Box B - middle - has two red wires, two black wires, one white, and ground. I installed an add-on switch there.

Box C - end - has one red, two blacks, and ground. I have not uninstalled the original switch yet as I am stumped.

Right now the light does not work. My questions are

  1. As a temporary measure, I want to change the setup to a three-way with just Box A and B. Can I just uninstall the original switch on Box C, tie the two blacks together, install the add-on switch with no neutral, cap the red wire in Box B that connects B to C. This is to just make the light works while waiting to fish a neutral wire.

  2. There is an outlet on the other side of the wall of Box C. However, the outlet belongs to a different circuit on the breaker box. Can I use the neutral from the outlet to wire Box C? I will hire an electrician to do the wiring/fishing.

Since you you just need power (hot and neutral) to your add on switch you maybe have enough wire but I will need more information.

What box does the power to the circuit come in on (sounds like A)?

What wire actually goes to the load and from what box.?

What wires run from what box to what box?

You may need to disconnect all wires and use a tester like a volt/ohm meter to determine all the above. If you are not experienced with a tester call a friend or hire an electrician.

You may have to repurpose some wires but its likely you have enough wires run. To repurpose a wire its best to apply the correct color tape to both ends of the wire, white tape to use a black or red wire for a neutral.

Below is a link to a discussion with a diagram that may help you understand what you ultimately need.

Thank you for the reply Scott. I have next to none electrical knowledge.

Power from the circuit goes to Box A.

It seems logical that the wires run from A to B to C. A has the hot power. B has two red traveler wires in it. I assume that one is connected to A and the other one to C. C only have one wire bunch coming into it. B have two bunches. A has several since it is a 3-gang box.

I have marked the wires in Box B and C that were connected to the black screw on the old switches in each.

I looked at the diagram in the link and I simply do not understand it. I can repurpose one of the wires to be neutral in Box C?

Hopefully @jhamstead , who wrote the community FAQ, @Navat604 , Who is an electrician, or one of the other electrical experts in the community will be able to help, but there should be a way to do what you’re asking. You probably won’t want to fish up the neutral from the other outlet unless it’s on the same circuit as the master switch, though.

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Yes you can as long as the wire runs back to Box A or B. You can tie the neutrals together in either place.

It sounds like the load wires are in box A which says you can use one of the blacks in in box C as neutral. Use a tester to determine which wire it is in both boxes and label it with white tape on both ends. Then connect it to the other neutrals. You will have an extra wire in box C if the Load wires are in box A.

I would say you have something similar to the drawing below. Look behind the switch for white wires. if you have 2 blacks, 1 red at Box A then most likely you will have 2 romex conduits which means there will be 2 white wires at this box. Do you really only have one white wire in each box or 2 white twisted together?
You mentioned power is at Box A and most likely on the COMMON terminal ( dark color screw) of the switch. Your load (black wire going to your light box) will be at box C on the COMMON terminal (dark color screw) of the switch.
Best way to do this is check with a meter for voltage at the COMMON terminals of both box A and C. Box A should have constant power at the COMMON terminal regardless of switches positions. Box C COMMON terminal should have voltage when light is ON and no voltage when light off.
If above is true. you can tie all the white wires together and that will be your neutral.
Tie black wires together at Box C and Box B. The black wire at box A that does not have power is now your Load wire.
Use the red wires as your traveler. Dont forget to tie the 2 red wires together at box B and use a pigtail to your Add-On switch.
I would not recommend using a neutral wire from another circuit due to various safety reason.