The voltages that you are seeing are probably caused by capacitive
coupling in the switches or wiring. In addition to the normal DC and AC
connectivity of a switch in the closed position, there is some AC
coupling in a switch across the open terminals, and AC coupling between
wires in a bundle. A neon test light probably draws very little
current, so it may be lighting due to this capacitive coupling. In
other words, it may be that nothing is wrong.

The voltages you are reading with a voltmeter are even less surprising,
even though the switches were in your pocket. Most modern voltmeters are
very high impedence, and find all kinds of voltages that have virtually
no current or power associated with them, even when the probes are just
lying around, touching nothing. The test lights are somewhat lower
impedence, so usually are more helpful. The capacitive coupling is
probably occuring from one wire to the other. These wires are probably
in the same bundle, so one wire capacitively couples a little voltage to
the other.

Hook up the light the way that you think that it should be hooked up,
screw in a light bulb, and try the switches. If the light works the way
you expect it to, forget it.

If you want to check for wires shorting in the wall, do it this way:
Disconnect all wires in the bundle at both ends. Use an ohmmeter to
check the wires for DC conductivity. They should all be open (very high
resistance, probably relative to each other. If the readings seem
flaky or indicate a problem, kill all the AC power in the house and
repeat the ohmeter readings. I would be surprised if you had a short,
but it is possible that a nail ran through the wire bundle, or something
else strange happened.

This is another case of a little knowledge and test equipment being a
dangerous thing. The more you check, the more confused you get, because
you are seeing very marginal effects, and then assuming that you have
some sophisticated problem. Don't take it personally, electricity is
simple at first glance, but gets more complex the closer you study it.
Electricians just wire it up, and are happy if everything lights up, and
probably only pull out the voltmeter if there is a problem.

Richard



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.

snip