On Mar 6, 7:29*pm, mm wrote:
On Sat, 6 Mar 2010 12:47:52 -0800 (PST), Mike Reed

wrote:
Hi,

I plugged our vacuum in to the GFI in the kitchen, and when I turned
it on, I heard a "pop" and assumed it was the GFI that needed to be
reset for some reason. Well, the GFI plug was acting completely dead.

I pulled it out of the wall, pulled off the line wires and tested
them
bare.

40V?!?!?!

If you are seeing an induced voltage, you are probably using a digital
meter, which are high impedeance, mabye 11MegOhms per volt. *

You mght want to measure the same place with an analog meter. They are
iirc 20KOhms or maybe 50KOhms per volt, either way must lower, so they
put a load on the voltage that dissipates the 40 volts but very low
maximum current that you may have, and the voltage will read
correctly, probalby very near zero.

Analog meters are those with needles that move. *

Except for FET-VOMs which are analog and use a needle, but have very
high impedance. I'm not recommending one of those, but I think there
have been none of those for sale for 25 years. *And they probably say
FET-VOM on them. * At the bottom of the needle area, it says the
impedance of the meter in ohms per volt.

For most things, I still like digital meters, which are auto-polarity
for one thing.

This circuit was fine this morning and has been installed for years.
We recently remodeled and moved a couple plugs around, but they've
been working fine for months (all on the GFI).

The breaker goes both directions with a positive click just like the
rest. This all started with the vac switch. I turned around and used
the vac on a different circuit with no problem.

Any chance someone's seen this before?

Thanks!

I agree with the induced voltage concept. I have encountered this
many times. Put a power strip onto your outlet, then put your
voltmeter into the power strip. If you get 40 V, then plug some
appliance into another receptacle in the power strip. Your voltage
will go to 0. The most likely thing to be wrong here is that your GFI
failed (a common occurrence). You can pull the GFI out of the box and
measure the voltage going to the GFI. If you have proper voltage
entering the GFI, then your GFI is dead. If you don't have voltage,
then your breaker is probably bad. Either is fairly easy to replace.