I have an old house with the old two-wire romex. There's a light at the top of the stairs, and a switch controlling the light at the bottom and another at the top of the stairs.
Here's my dilemma: Both switches and the light were replaced at the same time. Each switch has 2 black and 2 white wires. One white wire in each was left disconnected. Now the light doesn't work at all. Where should I start in troubleshooting? The new switches are 3way switches like the old ones. The new light is a plain 2bulb ceiling fixture. I have a wiggy tester, but don't really know what readings to expect.

 

You said that each switch has two black and two white wires. That sounds a bit like the old Carter System, a very dangerous wiring system. But you say that one white wire was left disconnected. Was that before, after, or both? Also please describe the wiring at the light. Did you pay attention to which screw on the old switch and the new switch was the "common" screw? The common screw is not in the same postion on all brands of switches. Why did you replace all this stuff?

You have a mystery. It will take a combination of information and testing to figure it out. Let's start with information.

 

I had the house painted and removed the fixture to replace it after the paint dried. The painter painted over the switches so replaced them (he did replace with 3 way switches). I couldn't test until after I put up the new light. He says the light or its installation is the problem and won't return.
One white wire was left disconnected both before and after. I'm not certain if the common is in the same place as before, but its the same look (Decora switches). I'm not familiar with the 'Carter' system other than I've heard its not used anymore. This wiring was done in the 50's or 60's, with the switches replaced in the 80's (all prior to my ownership).
At the light, there are 3 white wires twisted together with a pigtail to the light. Also, there is a single black wire going to the light. I can't tell which wire comes in with the black or anything else since this is the top of the stairs and the end of my 16-ft ladder. I attached the new light to the same wires as the old one though.

 

Three whites and 1 black at the light sounds odd. Please confirm this. Use your wiggy to find the hot wire. Is it at the light or one of the switches. I suspect the light.

 

Oh boy. This has a checkered past. It's not going to be easy. Unless you really, really want to figure this out yourself, an electrician can probably sort all this out in about 15 minutes.

If you want to figure this out, take it one step at a time. Start by labeling all the wires in all three boxes, and making a detailed diagram of the existing connections. Then with all wires disconnected in all three boxes, only one black/white pair should test for voltage between them. Start by figuring out which pair this is.

 

Well, I haven't gotten back to the top of the ladder yet, but none of the wires at the switches register as hot.

 

So it sounds like power must come in at the light. I suspect that, when you get back up the ladder, you'll find more than the three white wires and one black wire you have admitted to so far. It also sounds like somebody ran out of 14/3 cable and did a weird arrangement of using two 14/2 cables instead.

So here's what it looks like maybe you'll find at the light. There is probably a 14/2 power feed coming in at the light. From there, two 14/2 cables run to each switch box. This would mean that you'll find five 14/2 cables coming in to the light. On two of these cables, the white wires would be unused (as is true at the switch boxes on the other ends).

But I'm just guessing. Tell us what you really find at the top of the ladder.

 

I've run a lot of 3-ways with 14-2 romex.
Back in the 80's, 14-3 was over twice the cost as 14-2, and my boss was too cheap to buy it for tract houses. But concientious wireman that I was, I always twisted together the travellers, then wrapped the common around them. Foolproof.
There was always that spare wire though.

Wiggys are fine, but sometimes they'll throw you, especially when there's no ground wire to reference to. Don't assume that a wire's not hot just because you have no reading across anything. There could always be a dropped neutral when you have wires untied. In this case, there may be no neutral at all in the switch boxes.

It's possible that the light box is what's powered. Nutty but possible. Then, one 14-2 goes to each switchbox, and one between them. We call this scenario "The Bermuda Triangle!!"

There would have to be more wires tied together in the light box though... The hot is probably tied to another wire buried back there somewhere.

Before you take anything else apart, the simple solution may be that whichever wire is paired with the spare in the switchboxes is your common. The other pair would be the travellers, going between switchboxes.

Do yourself a huge favor and get a tick tester. You can find the hot wire without a ground reference in a fraction of the time. Fluke makes an excellent one. Well worth it.

Hope ya sort it out!

 

polyhedral, is the Bermuda Triangle code-compliant?

 

The switches were changed in the 80's or so, but the wiring is *obviously* original. It appears to be in good shape, but it is old.

I've been back on the ladder. The black wire is also a pigtail with two other wires. But I can't quite reach it, and can't get a taller ladder into this tight stairwell (I had to buy a new folding one to do this).

So, to sum, three pair of black/white wires into the light box. Dropped the wiggy on the tile floor so couldn't check for hot (wiggy's dead). Each switch box has two white/black wire pairs, not testing hot (with the wiggy before it died).

Everything does point to the 'Bermuda's Triangle' situation. Is this safe? Keep in mind that this is the old-style romex with no ground wire.

Also, where can I get a fluke -- at Lowe's? I do still want to test the wires up top to be sure, and I'll retest the switch wires.

 

Greenlee also makes a tick tester. Only $15 at Home Depot. But you may not need one for this project.

It does indeed sound like you have a Bermuda Triangle. So the problem is likely at the switch boxes. Go to each switch box. Find the black wire that comes in the same cable as the unused white wire. Make sure that this black wire is the one attached to the black screw (the common) on the switch.

 

Not only is it code-compliant, it's also specified for recording studios and server rooms where ground loops are of particular benefit!!

 

Thanks for the guidance John & polyhedral. Unfortunately, it didn't work. But I learned a little!
However, I did get a new tester and stretched at the top of the ladder to test the ceiling. None of the wires tests as hot. I retested the switch wires -- ditto. Now, I've also realized that I have an outlet in the next room that doesn't have power anymore either (the painter sprayed the entire house along with most of the outlets). Apparently, when they were replaced he used the backstab connections. I'm now trying to figure out which outlet is on the same breaker prior to these and hopefully switching the wires to the screws will fix the problem.

 

If you have a Sears store nearby, they used to sell a book on home wiring. This book contains multiple ways of wiring 3-ways. I think there are 5 different ways. This book helped me solve a 20 year old 3-way problem in an old farm house.
Chances are it was wired right and someone screwed it up. You will need to trace all the wires at both switches and the light and mark them accordingly.

On new construction, I have always wired 3-wire between the switches. It's the easiest and safest way. The cost is a buck or 2 extra. Big whoop.

 

Also commonly called a "cold" or "california" 3-way. It's just one of several compliant ways to wire in cable, as much as a "standard" would help for troubleshooting, there won't be one I'm sure.

Of interest, but absolutely no relevance , are some of the 3-way switching systems used with old KT wiring. If you've never seen a "Coast" 3-way, consider yourself fortunate. In fact, we see a lot of 3-way questions around here, perhaps we could diagram and sticky some of the more common types as reference material for these posts?

 

I could be wrong, but I've always thought the "Coast" 3-way and the "Carter" 3-way were two names for the same thing.

 

My reply regarding ground loops was of course tongue-in-cheek.

Circular wiring is not a good method, even if code-compliant. Ground loops can be a severe nuisance, but not a hazard per se.

I'm not sure how 3-way wiring would violate code unless you mixed circuits, overloaded a box, or switched a neutral.

 

I finally found my problem. Before calling an electrician, I decided to go to every replaced outlet and change the backstab connections. When I pulled the last outlet, I found a broken wire. You guessed it, after stripping the end of the wire and screwing it to the outlet, my 3-way switches and the other powerless outlet all worked. And, now I feel better that all of the outlet connections have been changed from backstab connections.
Many thanks again for all the help.