I have a 4Way lighting circuit that serves a single 3 bulb fixture via 2 and 3 wire BX cable. It is wired with two 3Way switches and one 4Way switch. I have never given it a thought - that is until yesterday when the fixture shorted out in dramatic fashion with arcing, smoke and melted wires. Amazingly the breaker never tripped so this got me thinking... & worrying...

I have determined that the black fixture wire is always hot, no matter the switch position. This is verified with both a volt meter and no-touch pen. The fixture is fed by a single BX cable with one black and one white wire so no mistaking feed wires for fixture wires during my tests.

The switches do turn the light on and off but it must be switching the neutral side for the black to stay energized - correct? Said another way - with a volt meter showing 115v and the bulbs off I can throw any of the 3 switches and the bulbs will light. Even more curious, there is no voltage (ever) at any of the 3Way or 4Way switch terminals even though the black fixture wire is still hot. I can kill the fixture wires with the breaker.

This seems totally wrong to me and may be the reason why I had trouble with the fixture and breaker. It's also difficult to troubleshoot because none of the white switch wires are marked...

Wiring

3Way #1 - Black, Red, White on Common
3Way #2 - Black, Red, White on Common
4Way - Black, White / Black, White

Thanks for any assistance -

My moms house has lights in the basement switching the netural side and its never had a problem, I did find it odd that it switches netural


But I'm not that experienced in residential wiring :)

Mekger - in order to have it wired right ,using two(2) three way switches and one (1) fopur way switch is the fllowing.
#1i you have comeing in from the power source( @ wire cable with a ground ) now i think it comes in threw the light bok on the ceiling, it could ,the power source come in threw the first 3-way switch,
If threw the ceiling light:: hook the hot black to each other ( it goes stright tthrew the box) hook the white wire to the white wire of the light it self, from the light down to the first 3-way switch use - 2 wire cable ,with ground :: grounds hook up togreather threw the light box and from light. From the black wire on the light itself - hook it to the white wire going down to first 3-way switch. Inside the light box -color code the white wires black < with black marker or black electrical tape:: now down at the first 3-way switch box on the wall. The same white wire that you color coded black up at the light< color code it here al:so < this is your hot wire < now going to the 4-way switch from here ;; the wire will be three (3) wires with ground, now lets do the wireing inside this switch box, the wire you color coded black hooks up to the black wire on the #wire with ground wire< it goes stright threw the switch box< the black from the light( that went stright threw the ceiling box hooks up to the switch on the end with one (1) screw< called the common terminalon the 3 wire you have a white wire from it that hooks up to the screw on the right bottom side ( holding the switch with the front of switch faceing you ) the wire is to be color coded black at the switch> ( now ) the red wire is called your carrier wire { it will be also hot} it hooks up to the bottom left side screw> ( ground wires hook up togreatheer < the green screw is the ground screw on the switch, :: the center $-way light switch is next; ( note - i hope you have fllowed me so far , its kind of hard doing it this way <i could do better faster and probably understand me better if i could just draw it out and send you a picture>but i haven't learned how to do that yet. Ok lets hook up the 4-way light switch, pull a ( 3 ) wire with ground wire from the last 3-way switch on the other wall to this 4-way switch;; on this switch you will have ( 4 screws for the wires to hook up to :: the black wire that passed stright threw the last switch box hooks up to the black wire comeing from the last in line 3-way switch:: the switch it self will be faceing you with the front of it faceing you again:: do the ground wires the same way again:: the red carrier wire ( hot ) hooks up to the bottom left side :: the white wire gets color coded again and it hooks up to the bottom right side ( you will pull a 3 wire cable with ground, from the last in line 3-way switch again :: as i said just above , the solid black wires hook up togreather and pass stright threw the switch box:: the red carrier wire ( hot ) hooks up to the top right side of the switch the white wire gets color coded again and hooks up to the top left side screw;; now comes the last light switch < it will only have # screws to hook to plus the ground screw which will be green ok hold the switch with the front of switch faceing you , there should be two (2) screws on top and one on bottom:: the bottom screw should be marked ( common terminal, the white wire will be color coded again and hooked up to the top right side of the switch :: the red ( hot ) carrier wire will hook up to the top left side and the solid black wire will hook up to the bottom right side

Ok now before putting switghes inside switch boxes :: go and turn the power on at the breaker box, if you have done as i wrote it all should work just fine < check oput all the switches and make sure its all ok :: if it all checks out ok turn off power at breaker box and then put switches in to boxes;; turn power back on and enjoy safly;; good luck and stay safe and god bless :: let me know by posting back on here if power comes from the first 3-way switch or if you have it all under control<:: f.b.e.

You are correct that if there is a single cable in the ceiling box, and the white in the first 3-way is connected to the common, the switch is making and breaking the neutral. That however would not be the reason for the short circuit you apparently had.
Suggest that you first determine possible causes for the short and repair.

You did not list which of the 3-ways is being fed. In that box there must be at least two 2 conductors and a 3-conductor. There also appears to be a conflict in what you have told us about the wiring in the 4-way. You said that there is a 3-conductor cable in each 3-way box with white connected to the common screw. That means that the red and black must be being used for the travelers wires. Those travelers (red and black) must be the wires connected to the 4-way. Also there must be two white wires in the 4-way box connected together with a wire nut.

Correcting the switch wiring should be easy. Connect the black of the incoming power cable to the common of the first 3-way, connect the white of the power cable to the white of cable going to the light, connect the white of the 3 conductor cable (going to the 4-way) to the black of the cable going to the light fixture.

Find and repair the short, verify these other things I have said are correct and let us know. Can provide wiring diagram is needed.

Thank you for the detailed responses...

FBE - I'm not at the point where I can simply rewire the entire circuit. Due to the age and construction of the house (plaster) I first need to figure out how the circuit is wired and see if there is a way to make the correct connections with the current wiring.

hkstroud - It appears that the feed line enters directly into the ceiling box given that it is hot when none of the switch leads are. But with out another bx cable heading out of the box for the switch leg this doesn't make sense.

"Those travelers (red and black) must be the wires connected to the 4-way. Also there must be two white wires in the 4-way box connected together with a wire nut." This is probable but there is no question that they must change color in a junction box somewhere. The cables supplying the 4way are indeed 2 unique BX cables both with a single pair of black and white conductors all attached to the switch. I need to find that j-box to determine how and where the black and red travelers change to black and white and head to the 4way. There are not additional white conductors tied together here for this circuit given the BX cable described above. There are neutrals tied together in the box with the 4way but these are clearly newer THHN for a switch and lighting circuit servicing a different area.

I will run through this again and see what I come up with. I did call an electrician that has done work for me in the past with the intention of having him diagnose the issue in the interest of safety. I am not an electrician but have done a significant amount of electrical work over the years. That said - I have a very good understanding of how this all works and the problem I am currently experiencing simply does not fit with how properly wired circuits behave.

As for the short - the wires in the box were in poor condition (old cloth covered) but no visible failure, charing, etc. The short was clearly in the fixture itself - in one of the metal bulb stands (candle type) which blew out the side from intense arcing. This inturn overheated the adjacent bulb stand causing the wires to melt there as well. I have to believe that a properly wired circuit would have tripped the breaker after all of this.

Well if the wires change colors there is little doubt that there are hidden connections some where. Also it sounds like that a single conductor was run outside the cables between switches. It may have been run from switch to switch or switch to fixture. Given all this, you can not assume that the neutral is being switched just because the wires are white. You will have to get out you meter and check every thing. If you have an attic space above or a basement below, you will probably find that the two BX cables go there and are connected to the 3-wire cables with separate conductor between the two boxes or connection points..