Reduced voltage in 3-way switch wiring

I opened the auxiliary breaker panel for that part of the house and tested the relevant breaker. My meter showed 120 volts on the output side of the breaker. At that point I put everything back together and told my friend that I was out of my depth. I don't even know what I would be looking for that would produce reduced voltage.

Stan

You checked between Scb (circuit breaker) point No.1 and point N and got 120 volts. Then you checked between point No.2 (3-way switch No.1) and point N1(N1 would be in same box as switch 1) and got 50 volts? Check power from point No.2 to a N on a known good circuit. If still 50 volts, problem is somwhere between point No.1 and point No.2. If you get 120 volts.the problem is in the N (white) wire.

This is a situation where four or five lights which are controlled by switches at each end of a hallway worked for ten or twenty years and now they don't. To me that rules out the answer that they were wired improperly. Furthermore, nothing electrical has been done to the house in at least a year.

I don't wire circuits so that a ground is ever used as a neutral. When I am testing a circuit to locate a problem, however, I often test disconnected hot and neutral (black and white, usually) wires against a proven ground. Sometimes I will use the plumbing if the house is plumbed with steel or copper. Usually I have to fall back on the ground in an extension cord which is plugged into an outlet on a different circuit. I do this so that I will know which wires I will be working with are carrying current.

If I put my meter across a black wire and a white wire and it registers a voltage drop of 120 volts, am I completely safe to assume that the black wire is carrying current and the white is the return? I wouldn't bet my life on it. That's why I like to know the status of each individual wire I'll be working with, and that's why I test each against a ground I have separately proven to be good.

I'm not talking about doing this every time I perform some uncomplicated bit of maintenance or repair. I'm talking about troubleshooting a problem that's a real head scratcher. I think you'll have to agree that if the brainpower that's available on this forum isn't sufficient to pin down the answer on the first go-round, the situation qualifies as a real puzzler.

All the best, Stan

Anytime you run into an under-voltage or over-voltage condition such as this, a loose neutral connection should be suspected. Especially if you see higher voltage in one circuit (or part of a circuit) and lower voltage in another.

Start by making sure you have a good bulb in at least one of the light sockets. This will ensure that you have one grounded conductor to work with. This should make it easier to determine which switch is fed from the panel and which switch is connected to the lights.

I believe if the house is wired per code, the switches must both be on the hot side of the light. (Otherwise you have a condition where the light socket is "hot" even though it's turned off.) As Slowpoke says, you can run into variations on this, but I believe these are code violations.

I don't have a code book in front of me to confirm that it's a code violation to have a three-way switch on the cold side of a light, but common sense says you don't want to have power running to a socket that you think is turned off. This is the way I was taught to do it in my 4-H class, which was at least five years before your book was published.

Best regards,
mark

Hell, where I grew up the cows carried lunch buckets between blades of grass! I think I was old enough to drive before I saw my first tree.

It may be a code violation now, but it wasn't 10+ years ago. When an electrician did a basic setup in my basement (just a couple of lights) that's what he did - had the feed going into a fixture first, then on to the three-way switches.

Really had me scratching my head as to how to add onto it when I finished the basement.