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MG TD TF 1500 - How to trace a wire?

In the course of installing my new wiring harness the past few days I've felt the need to trace several wires from one end, through the harness, to their other end, for my own understanding if nothing else. I've been using a simple AA battery and a multi-meter to do this. But there has to be something better. What kind of tool am I looking for? Or am I not using the meter as intended? It has it's own battery I assume to just power it's led screen, but is there more to it perhaps?

Duh?
Ed
efh Haskell

Easiest method Ed, is to get a little multi meter with a continuity sound option. Make up a long test wire with an alligator clip on both ends. Clip one end to the wire and the other to one lead of the test meter probe. Touch the other probe to the other end of the wire. If it makes noise then you have a complete circuit.
LaVerne

the ohms meter part will work to determine where the wire comes out.
Tom Maine (TD8105)

the ohms meter part will work to determine where the wire comes out.

That's what I use also! An ohm meter. But, I do like LaVerns idea. Don't have one with sound, but it's now on the list. PJ
P Jennings

What ever way you do use, please make sure that you don't loose any if the Lucas Smoke!!!!!!!!!
Steve Wincze

I use a simple continuity tester (pen size, bulb/AA battery) and long wire. Then flag the wire with tape and make notation as to what it attaches to.
David Werblow

A continuity tester w/beeper is easiest, (turn the tunes down in the garage...LOL). Radio shack should have a cheap meter that will do that (around $10).

Just for grins ...you could go this route.
Fox & Hound, in case you have never seen one.
Just slightly overkill for an MG harness. Lets say you have oh, 10,000+ runs of wire in a building and hired somebody that wasn't the sharpest rock in the box to put numbers on both ends. (normally the "same" number on both ends of the wire helps a lot!) With the fox set to "warble" mode you can find the other end with the hound. The hound gets a progressivly louder & steady tone untill you find the other end. Neat thing about this one is it will "sniff-out" a wire in a bundle without actually having to make direct continuity with the conductor in the wire jacket. Guess it would work on an MG ...great if you happen to have one over a mile long!
LOL


David Sheward

Tom or Paul,
Okay, my meter has several "Ohms" settings you can turn the dial to. All I remember from high school is ohms is a measure of resistance? How do you use this to trace a wire?

Duh (again),
Ed
efh Haskell

Ed, here's a case where it really doesn't matter which scale you use. Direct continuity is essentially zero ohms. You'll see that zero is at the far end of all of your ohms scales. Habitually, we generally use the lowest scale when doing continuity tests. Bud-retired EE.
Bud Krueger (TD10855)

Ed ,
If you have am "old school" analog meter simply touch the leads together and note the reading on the meter as you change the range. That's what you will be looking for. However don't forget you may get "resistance" if your checking a circuit hooked up to just about anything so make sure you "confirm" yours by breaking the circuit to make sure the continuity goes away when you do so.
David Sheward

Hmmmm

I can see the value of an ohm meter to find a short in the loom. But other than that, every loom I've seen, when laid on the chassis, has wires of the correct color that simply fall into place. Initially, there were a couple of wires I marked because I had a custom loom built up, but I soon realized the folly of that effort and simply striped the wires with some paint.

Why folly? because you have to be able to run the wires through grommets, and the tape flags will mess up that effort.

warmly,
dave
Dave Braun

I'll play with my ohms. Thanks guys.

Dave, remember this is my first loom and some things are confusing. For example, there are 3 white and 4 solid greens going to the regulator. Being type A, I must know from whence each originates even though the diagram clearly shows it. Once I prove to myself I know what's going on I think I can trust the diagram more. For now it helps to see that meter say something to me. Plus it's cool to watch.
efh Haskell

Ed, do you mean like this? Bud


Bud Krueger (TD10855)

Whats all this color coding crap?


LaVerne

I like that LaVerne! You can't go wrong, as long as your looking for a purple wire! LOL.
P Jennings

LaVerne, that is what my wiring loom looked like before I went with a new one. Mine was mostly red and black.Easily available at your local hardware store.
Tom Maine (TD8105)

LaVerne,
I think the same guy wired my TF!
He color-coded mine though ...
The green wire turned into a yellow wire, then red, then black, then blue, then brown ..all in the space of about 3 feet.
I think he was "short" (pun-intended) on wire but had lots of butt-connectors and looked like he used a couple rocks to crimp them.
Must not have had a hammer!
Also did not have electricial tape ...who needs it if you have a good supply of masking & scotch tape so you can wrap it around the steering shaft.
David Sheward

I'm in LaVerne's camp only with "stock" red/black/blue home brew "loom" (and that's a loose word for the jumble!) and a few connector strips for gnds and hot re-distributions, brake light relay,.... I think all my blacks are my "grounds"! You should see my "schematic" Ha!
Randy
Randy Biallas

In fairness to the guy the wires were mostly tagged but I had no reservations about removing the whole mess with a pair of snips. Wondered though if they had a close out sale an bulk purple wiring?


LaVerne

Here was my mess a year ago. I had wild ideas about being able to use this stuff as a guide to installing the new harness! HAH! It hasn't been out of the "old parts" bin since. All you need is a good colorized blown up diagram and a new loom. It wasn't that hard once you got rolling.


efh Haskell

Dave S. -- Have never seen one like that!! But it seems like a good way to do it. I have seen a few that put a signal on a wire and then you sniff around to see where the wire comes out. Bought one once but it didn't work like I wanted it to. So I don't even know where it is now.

Spent a very pleasant Sunday afternoon ohmmetering out a new wiring harness. Put tape labels on all the wires using the schematic and wiring colour code. When I installed it, I rolled the tape labels around the wires and they went through the holes OK. Car has run fine for years.

Now if I want to disconnect the fuel pump I have to pull all the wires from the fuse block (late 1952) and jumper them to 12 volts to find the right one. No big deal.
Cheers,
Bob
Bob Jeffers

Used a bit of purple here also:
LOL


David Sheward

David, that must be for the high speed internet computerized ignition system on the TD. Heard about it but had not seen it till now...
Tom Maine (TD8105)

Lets see...lots of purple wires....lots of white zip ties......you ever own another TF Dave?


LaVerne

This thread was discussed between 08/03/2011 and 10/03/2011

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