testing random electrical connections

[BlueRooster]

Is there a way to test different wires to see what they are for? I have a wire that is wrapped in tape, it is dangling and it has an electrical connection at the end of it. It is in the engine compartment on the passenger side and I cannot follow it. Is there a way to use a multimeter to check current, or at least narrow it down to an area. I am not a good electrician, but Im trying.

If you want a picture I can get it.

Dane

[mrmustang]

Dane,

It could be as simple as an unused accessory circuit (electric choke, foglights, neon lights, etc)........


Bill S.

[Cobra20646]

Like Bill said, it could just be an unused wire. First thing to do is check to see if it has voltage on it. If it's not going anywhere, it shouldn't have voltage on it, but that's no always the case.

Connect a volt meter between the wire and chassis ground. Then start the engine, turn all the dash switches on and off, blow the horn, until you see voltage on the meter. Depending on your fuse box, you may have to stick a fuse in where none are to see if that's where the other end of the wire is. Chance are you'll find it. But if you don't, find a friend in the telephone business.... they have a gizmo that connects to one end of a wire and sends a signal to a hand held receiver..... they can run it alone the car and follow the signal to where ever the wire goes.

[G.R.]

Jim is right phone guys and installers of other type low volt equipment and lines use these gizmos. They work off of usually a 9v battery and send a "tone" along the wire with the "reader" you can follow a wire to it's source or in some cases a break in the wire. The one phone and wiring pros use are rather expensive but for about $30 you can get one that works well from places like Radio Shack. I bought one about 10-12 years ago and have used it to trace hidden wiring in boats and recently on the car I bought to straighten out the wiring.
Easiest way I've found to trace wires

[BlueRooster]

Thats seems like a pretty cool tool to have in the garage. I'll bet that if word gets out that you have one, you could probably charge your buddys rent. The thing will pay itself off in a couple years.(kidding). Does anyone know the actual name of the device?

BTW, thanks for all the responses.

Dane

[G.R.]

Dane I think it is called a circuit toner, I looked at mine all it says is Radio Shack, no numbers or anything. It is a 2 piece tool, one end has a alligator clip you attach to an exposed wire or a pin probe you can push into a connected wire sheath this piece then emits a "tone", the "reader" picks up the tone and you can follow the wire to it's source, works ok but not more than 6'' away from the wire though--difference in quality between the RS version and the pro version. The sending unit uses two AA batteries and the reader uses a 9v.

[Cobra20646]

Dane,

The one the pros use........

http://www.mcmaster.com

Tone Generator - part number 57175T1 $34.95

Standard Amplifier - part number 57175T5 $63.06

Just enter the part number at the home page to be taken to the items. Not cheap, but worth their weight in gold if you need to trace wires.

- Jim -

[badrich]

Thanks for the info on McMaster, Jim. I recently spent an afternoon finding out why my Lucas (Prince of Darkness) headlights stopped working. If I didn't have my EE friend doing most of the work, I'd probably still be searching. We found a faulty 30W circuit breaker ($3.50 at Kragen's). I plan on ordering the tone generator and standard amplifier ASAP, before the Prince strikes again! Rich

[G.R.]

You'll never regret having one in your tool box.

[sllib]

Rich;
Don't use a toner on a live circuit; it could lose all it's smoke. If the wire you want to check goes back to a common circuit or ground, ALL the wires in that circuit will have tone on them, confusing the search. The home places have testers for live circuits. You may have to jury-rig the connection.
Bill Stradtner

[Steve R]

we refer to the tone tool as a "fox and hound" in the aviation business.
We also use a T.D.R (time -domain reflectometer) to look for shorts and opens in long wire runs. I'm not aware of a cheap one of those though.
Steve

[Excaliber]

I kinda like Bills approach the best. If everything else works who cares where the "extra" wires go. Cars always have lots of "extra" wires for accessories that MIGHT have been, but weren't on THAT car.

[strictlypersonl]

If the wire is live, you may be able to use a cheap short finder like this one. .

[badrich]

Thanks for the heads up, Bill. It sounds as if turning off the juice at my battery cut-out switch would be a good idea before using this expensive test gear. I would hope that they would include some detailed instructions with this stuff. And unlike some guys, I always read the manual first. Rich

[Rodney]

Check the color of that wire in your wiring diagram section of the SPF owners manual, it will tell ya what its for.

[Steve R]

Hey!
This is a technical forum. That would be too damn easy.

[Rodney]

Opps!