# 4-way switch - common wires are not normal

I am not an electrician and I have read all I can about 4-way switches/circuts. I am trying to replace a 4 way switch + 2 three way switches with zwave. I have done other 3-way installations (with only two switches) but this has me stumped. Once I can determine where is line and load, I can do the rest on my own.

As I understand, one of the 3-way should have a constant line from the breaker and the other 3-way should have the load going to the light. I have a Voltage Tester (not multimeter).

Here is the problem -

• When the light is on, I cannot detect any voltage on any of the three terminals of the 3-way switches. Two of the 4-way switch terminals have voltage.
• When the light is off, 1-2 terminals of the 3-way switches have voltage.
• I haven't run all the permutations but it is very weird and not following anything I am reading online.

What the hell? :) The way I have been testing other 3-way circuits is that the terminal that always has the voltage whether the light is on or off is my line from the circuit breaker. The terminal that only has voltage when the light is on is my load to the light. The other two are travelers. I was hopping to apply this concept to my 4-way circuit (at least to the ends of the circuit, I know the middle has 2 pair of travelers) but it's not following the laws of physics :) All 3 switches work - I can open and close the light from any switch.

It is supposed to work like this

My 4-way switch

My first 3-way switch showing no voltage when the light is on

My second 3-way switch showing no voltage when the light is on

I would really appreciate any pointers in the right direction!!

• Can we have photos that look dead-on into the backs of the boxes involved? Mar 14, 2018 at 3:17
• That non-contact voltage tester will run you in circles on a 3-way or 4-way switch. Use a wired 110/220V Voltage tester (not a DVM). These are as little as \$4 and will tell you unambiguously which terminals have 110V to ground or neutral (you'll have to carefully unscrew the neutral wire nut without shorting it to one of the other exposed wires). Mar 14, 2018 at 18:39
• @Stanwood The nomenclature for the measuring device is called Analog Meter as opposed to a Digital Volt Meter.
– Ken
Mar 15, 2018 at 3:00
• @Ken It is? I have an analog meter and it looks quite different (img.banggood.com/thumb/view/upload/2014/11/SKU168322/1.jpg). Both the analog and digital volt meters have a very high impedance and will pick up stray voltages on open wires leading to more questions here. So I generally recommend DIY electricians to use a lower-impedance voltage tester that is meant to detect 110/220V rather than 12V. Mar 15, 2018 at 3:06
• @Stanwood I have a similar analog meter, no batteries needed for it to work. Mine measures 250VAC max ; cost me about \$3 and it works fine. Given stray or loose wires Analog meters will load the circuit and the needle will fall to zero. As you know DMMS with out a LoZ will give an incorrect reading because they are high impedance devices. I have never liked the 'voltage testers' because they never tell me what I really have and for the price of a REAL meter what is the point. A LoZ Digital Meter works but a DIY'er is not generally going to have that kind of investment in a meter.
– Ken
Mar 15, 2018 at 3:34

It sounds like the voltage tester has issues. There are other ways to identify the wires.

Usually 3/4-way complexes are a mess (not least because the wire color does not correspond to the purpose in any way). But your 4-way switch makes this surprisingly simple: both pairs of messengers are on the red+black wires.

So go to the remaining 3-ways. Find the red+black pair that goes into the same cable: those are the messengers. The remaining wire is the always-hot or switched-hot.

You will also note the messengers are on brass screws, and the always-hot or switched-hot is on the black screw.

This is so weird!! (two 3-way circuits next to it and other 3-way circuits in the house, I can detect everything fine)

With everything else the same, load wire disconnected (confirmed light is off), I can detect voltage on the load terminal and every other switch on this 4-way circuit and it terminals has the voltage it should have according to the picture above.

As soon as I connect the load wire... no voltage detected :)

Anyway, I know what is what now and can proceed. Looks like the non-contact voltage tester is unreliable in this case.

• The reliability of non-contact voltage detectors varies greatly. Units with batteries tend to be better than self powered versions. The tolerances and quality vary greatly tho, some are much better than others. Mar 17, 2018 at 1:44