"Stormin Mormon" wrote

stuff snipped

Other is to energize the wire with 110 VAC power like you
suggest, and then use a line voltage detector.

http://www.harborfreight.com/non-con...ter-97218.html

Gack! I agree with Mr. Morgan. A line voltage detector won't work through a
foot of dirt, AFAIK. Energizing a wire previously used as a low-voltage
speaker wire with 110VAC is not the preferred method in any case. The wire
could be compromised, hooked up to controls in an unknown area or even part
of some previous, ill-conceived "shock a burglar" system. Best to use low
voltage tools like the Fox/Hound set or something similar.

Even that advice comes with a caveat. We don't know what the OP wants to do
with this wire. If it's to carry significant current, like a space heater,
I'd be tempted to pull up what exists and re-lay cable of known good quality
installed as per the NEC and/or the local rules governing outside wiring,
and that usually means putting a GFCI in the loop somewhere, at least.

The OP has no idea if the wiring was being used for speakers because it's
unsuitable to carry line voltage because of damage or some other problem.
No way to tell if it's spliced every 20' with nothing but black tape or wire
nuts or has long gashes in it from being pulled against some sharp edge.

I wouldn't, in any case, energize it with line voltage in the hopes of being
detectable by some means other than a standard wire tracing kit with a tone
generator and a matching receiver/tracer.

--
Bobby G.