Ivan:

Though there may be other reasons for getting the measurements you see, I would
propose the following:

You are probably measuring the voltage with a high impedance voltmeter, which
doesn't put much load on the circuit under test. With a decently long run of
wires running parallel, they act much like a transformer, which means that you
will put an actual 117 (or so) volts on the hot wire, and induction will cause
the floating wire to have a voltage induced on it. However, the amount of
current available on the floating wire is extremely low. So low, in fact that
it won't be able to cause a problem.

If you were to connect two light bulbs to the "shuttle wires" you'll find that
when you apply 117 to the red wire, the bulb connected between the red and white
wires will illuminate, and the voltage on the black wire will be zero. If you
apply 117V to the black wire, the bulb connected between the Black and White
wires will illuminate and the voltage on the red wire will be zero.

Given a high impedance meter (or neon bulb) you can get odd indications,
particularly if the run of wires is long, which increases the efficiency of the
"single turn transformer" that is being created.

Now, the above explanation assumes that when you made your measurements, you
verified that the "Shuttle Wire" cabling doesn't go anywhere else than between
the two switch locations and the light.

From your description, it sounds like things were actually wired correctly
(using a multi-color, 4-wire cable) instead of the slipshod stuff I've run
across over the years.

What I would expect to see is a 3-wire (Ground, Black, White) cable coming into
your "hot" swichbox from the breaker panel, and another cable with 4-wires
(Ground, Black, Red, White) going to the lamp fixture box in the ceiling. From
the Ceiling box there will be another 4-wire cable (Ground, Black, Red, White)
going to the remote switchbox. At the hot switchbox, the Ground and White wires
are connected to the Ground and White wires of the 4-Wire Cable and the ground
wire should be connected to the box and/or ground terminal of the switch. The
Black wire of the 3-wire cable goes to the common point of the 3-way switch, and
the black and red wires of the 4-way cable go to the alternating contacts of the
3-way switch. At the ceiling box, the ground, black, and white wires are each
connected to the corresponding colored wires of the remote switch cable, with
the two white wires (one from each cable) connected to the lamp fixture. The
white wire from the remote switch cable should have a wrap of colored or black
tape on it to indicate it is the "hot" wire from the remote switch. At the
remote switch box, the ground wire should be connected to the box and/or ground
terminal of the switch. The black and red wires go to the alternating contacts
of the 3-way switch, and the white wire, (which should have a wrap of colored or
black tape on it to indicate it is the "hot" wire from this switch) is
connections to the 4-wire cables, everything should work properly.

If this doesn't make sense, or you have any confusion at all, you should have a
qualified electrician come in and check everything out. It's better to be safe
and spend a few extra bucks than be dead or to cause an electrical fire because
you wired something wrong. Also, in some areas, it may be illegal for you to
do even the smallest electrical addition or change unless you are a licensed
electrician. Always be safe and follow all applicable laws and regulations in
your area.

Disclaimer: Don't do this at home. Always have a professional perform any
electrical or plumbing work. I'm not licensed to perform electrical work in
your location, so the above is for educational purposes only and not to suggest
you can actually do your own electrical or plumbing work. If you do ignore this
warning and do it yourself, don't bother to sue me because I don't have anything
to get anyway, unless you would like to take over my bills... 8-)

--Rick

Ivan Vegvary wrote:

I'm trying to wire 3-way switches on either side of a ceiling lamp. The
power initiates at one of the switches. I've got the wiring scheme figured
out but I have a problem.

Prior to installing the lamp fixture I decided to check the switch functions
(at the ceiling lamp) with this simple $ 1.00 neon tester. With the switch
on the neon tester gives full brightness, with switch off it still lights
up, but very dim.

Disconnected all of the wires everywhere and come up with the following:

At 3-way switch I have a ground, black, red & white wire (only the ground
and the white have been connected to others). I'll call the black and red
wire "shuttle wires". These same wires are dangling, unconnected, at the
ceiling. Nothing is hooked up. Ground to power is 118.5v. White to power
is 118.5v. Ground to white is 0v. IF I connect the "shuttle" black to
power (as if the switch would also do) I get 30± volts on the totally
disconnected (both ends) red "shuttle" wire. An ohm reading between the
unconnected "shuttle" wires reads open (my ohm meter only goes to 20
megohms).

Is the only answer that somewhere in the wall the black and red "shuttle"
wires have slightly shorted, giving me 30± volts? These are brand new walls
in finished space and I'd hate to tear out the sheetrock and wires. Note
that all of the above is with the 3-way switches in my pockets, i.e.,
totally out of the equation.

BTW, if I ignore all of the above, I get 60±volts at the ceiling in the
switch off position. Turning either switch to the on position gives me my
118.5v. The 60 volts is not enough to light a bulb, so, I am tempted to
ignore it. Is this dangerous?

All advice greatly appreciated.

Ivan Vegvary