How to trace wiring inside residential walls? Is there a way to do this?

[cvanc]

Hi all-

I want to trace some dead (disconnected) low voltage wiring that is in the walls of my house.  The wires are open at both ends, not connected to anything.  I have access to one end to inject a signal if needed.  The other end... well I've only got guesses where it might be.

The house is typical wood frame & plasterboard construction.  This is old thermostat wiring from my furnaces; I am looking at installing new 'stats and re-using these old lines might be very handy.  Is there a way I can find the other end of these lines?  Thanks.

[MikeW]

If you just want to find where they start and where they end up, not what path they actually take through the house, link the ends and test for continuity.

[jsmn4vu]

Is there a way I can find the other end of these lines?  Thanks.

Consider connecting an RF generator to the end you have access to, and using a transistor radio to trace their path.

[wraper]

Connect one end (all conductors) to the mains live wire and use some non contact voltage detector which have high sensitivity.

[wblock]

http://www.sentex.ca/~mec1995/circ/foxhound.html

Or the real thing: http://www.triplett.com/shop/fox-hound/

[dadler]

What you want is referred to as a "toner".

[Richard Crowley]

What you want is referred to as a "toner".

But remember that most of those proximity wire tracer devices require VERY CLOSE proximity, practically touching the wire insulation.  It seems quite possible they don't work at distances involved when trying to trace wire routes through typical wall construction.

[Fungus]

Connect one end (all conductors) to the mains live wire and use some non contact voltage detector which have high sensitivity.

...and hope the house doesn't burn down when you do that. 

[Don Hills]

Connect one end (all conductors) to the mains live wire and use some non contact voltage detector which have high sensitivity.

Only do this if the wire is mains rated... the OP said it's thermostat wiring, it could be low voltage insulated only.
Also, using mains, you won't know if you're detecting the thermostat wire or a mains line to an outlet.

[Seekonk]

What is it worth to you?  There are devices that run well over $100.   AS suggested, a signal generator is likely the best option with an AM radio.  Might need a little amplifier.  I have a water heater that operates on 500Hz PWM.  I can pick that up on AM if I get within a foot.

[edavid]

I have had success connecting a function generator to the accessible end, and waving a scope probe at the other end.

It helps to set the FG to sweep, for a really distinctive signal.

[Richard Crowley]

Connect one end (all conductors) to the mains live wire and use some non contact voltage detector which have high sensitivity.

...and hope the house doesn't burn down when you do that. 

Well you could connect it through a 1M resistor.  That would prevent any burning, shorting or heating.

But trying to trace mains frequencies (50/60Hz) is very inferior to using higher (RF) frequencies like broadcast AM (LW) or FM.
Wireless transmitters for AM and for FM are widely available on the internet. Both off-the-shelf and DIY circuits.
The DIY transmitters take only one or two transistors and a handful of penny components.

[Falcon69]

I had a problem in the house. One of the plugs were blown out, but couldn't tell which one. I didn't know the path of the wire to the circuit box and the wire went through several other plugs, though, I didn't know which ones.

I bought this...
http://www.homedepot.com/p/Sperry-Lan-WireTracker-Tone-and-Probe-Wire-Tracer-ET64220/202520187

from Home Depot, and it worked. From the plug that did NOT work, I traced the wire by waving the wand a couple inches from the wall. I followed that wire to one plug, no power at that one. Traced the wire to the next plug, which was working. Took the face plate off and removed the plug. It was bad. It was working, but the contacts were melted for where the wire feeds out to the next plug. Cheap plastic manufactured home plugs.

I am in the process of replacing all the plugs in the house. This was the second plug I've found that had melted. Lucky house did not catch on fire.

That tool, was worth the $40.

Basically, You plug the base (using the leads) into the plug, and wave the wand along the wall.  The base sends a signal down the wire, and the wand picks it up.  There are better, more expensive models that do this, but this one worked for me.

Hope that helps ya.

[Muttley Snickers]

Beat me to it, I was just going to post a link to your thread.

https://www.eevblog.com/forum/beginners/home-electric/

We use these Aegis CZ-1000s linked below but as Richard mentioned they are limited in depth range but there are a few tricks to improving the range, I also have a large collection of other toners that operate at various frequencies which are sometimes better suited.

http://www.aegis.net.au/products/circuit-tracers/cz1000

[Falcon69]

lol.  I totally forgot that I posted here for that. Thanks!

My mind isn't what it used to be.

[cvanc]

Many thanks to all for the suggestions, I found one of the Triplett Fox & Hound units for a good price http://www.triplett.com/shop/fox-hound/ .

I'll post back in a few days and let you know how well it worked.  Thanks again.

[cvanc]

...Oh, and Falcon69, I'm with you on the spiders!   

[Falcon69]

Spider!  Where!? 

[cvanc]

Spider!  Where!? 

Right there behind you!!

Just kidding.  So this Fox & Hound I got worked beautifully, the wires have all been found with no difficulty at all.  I'd estimate the range, through typical residential walls, at a good two feet.  Thanks all for the input.

[wblock]