I've got a residential circuit with 3-way switching for one room's lights, 3-way switches for a second room's lights, some outlets, and a light-sensing switch for an outdoor light. All the 3-way lamps are showing voltages I can't sort out.

Here's what I get with a digital meter and a known earth:

Ground, White, Black

Light #1:
UP/UP= G 59v, W 120v, B (milivolts)
DOWN/UP= G 42v, W 120v, B 35v
UP/DOWN= G 42v, W 120v, B 37v
DOWN/DOWN= G 34v, W 120v, B (mil)

Light #2: Testing socket
UP/UP= B 120v, W (mil)
DOWN/UP= B 79v, W (mil)
UP/DOWN= B 79v, W (mil)
DOWN/DOWN= B 120v, W (mil)

I want to get this thing solved without disturbing the occupants much or cutting into the walls. Does this look familial to anyone?

First of all, whats not working? Are the 3ways not operating properly or are you having trouble with dim lights?
Not sure what to say about the odd voltages until I know more about the problem.
You should also think about calling a licensed electrician.

I agree that a licensed electrician should be solving this case, not sure if you are licensed or not. From the sounds of it, it seems you have a series circuit. My guess without actually seeing this is someone must of wired the neutral into the loop, so when the switches are turned on a certain position your carrying a series circuit through. Are you getting dim lighting?

I'm not an electrician but have done most of the renovations and maintainence for this house. The customer initially asked me to replace an "ugly" tracklight with a new fixture (light #1). I pulled the old fixture and tested the wires - this is when things became interesting. I asked if it had been working. The customer then told me the bulb "blew up and threw the breaker." The tracklight was mounted on the ceiling some distance from the (open) box, with two wires connecting it. I checked the tracklight, and it's OK. A bare wire ends at the box. So, that's a single cable (black, white, bare) to this box, and I'm sure it comes from a buried junction box somewhere.

Everything on this circuit works, but I'm hesitant to just put in a new fixture, because I can't make sense of the voltages listed above.

Much of the lighting in this house has the neutral switched.

Quote---Much of the lighting in this house has the neutral switched----

Another good arguement for calling an electrician

I am a bit confused you state 3way switching and then you say 3way lamp which do you have
if you have 3way switches then it seems you are using the ground as a load carrying conductor.Now is time to call an electrician

Gotta go with txsparky on this one. Switching the neutral can give you the odd voltages. My advice... call a licensed electrician.

yea i agree, you need an electrician.i come across 'little' problems like this all the time, generally just after the general builder(jack of all trades-master of none) has cashed his check and moved his phone number to the next telephone box down the road.

Looks like something is very badly miswired.

To have even a chance of figuring this out, we will need to know what wires go where (how many cables in each box, which color goes where). Also, if you could do the measurements with a load on the circuit (measure the voltage across a pigtail lampholder) and with the other bulbs removed, so we can eliminate any phantom voltages.

We already know that light one has problems - even if the neutral is switched there shouldn't be any voltage on the white wire unless we are seeing voltage thru the other bulb and they are in series. Voltage on the ground wire is even worse.

I agree with calling in an electrician on this one. It sounds like there are too many problems, not only on this circuit, that should be fixed for safety reasons.
/mike

Thanks everyone, for the advice. This kind of problem needs to be frowned at, in person, by someone who can trace a lot of paths in mind. That's not me.

I am the "general builder(jack of all trades-master of none)", andylea, and have done both new electrical work and some upgrading in this house. I'm sorry that because in your specialized function you only get to see the problems, you have a bad opinion of people like myself. Consider all the work done by non-electricians which you will never see or care to notice because it was done perfectly. Consider people like myself who do check back on their work and take full responsibility for it. You don't get to see that.

Now I'll put the circuit map and testing data legibly on paper so the electrician won't have to do all of that over again. With luck, the answer will be plain to someone with more experience.

Sounds like readings from a High Input Impedance DVM [Meter].

If things are functioning correctly, the Hi Z DVM readings would be somewhat normal.

If things do not function properly, it would either be a wiring / connection problem or problem[s] with devices - such as switches, lamp holders, motion detectors and such.

Scott s.e.t.

Neutrals tied together in the same box that are from different circuits can cause weird readings too, something common in some old work and perhaps some new work with green helpers! Equipment Grounds should all be tied together, Neutrals, not necessarily so...

(Guess I'm in the "Foresee all bad circumstances before they happen" mode with this new helper experience coming up... and remembering some of my own green mistakes!)

Kobuchi,

The voltage readings don't make sense, given the info you've supplied. More data is needed. This text based forum is not made to handle this. You get high marks for asking the question. The recommendation to bring a pro to the job site is not a rebuke - The problem, as you state it, in my experience, has all the earmarks of a really good puzzle worthy of even the best electrician. Caution flags are raised by the symptoms. Don't let this one coast. No shame in passing the baton.

Al