Tracking down a short (running lights)

[MTMike]

1/2 of the running lights have never worked. Fuse in that slot blows immediately after turning the running lights on. The other half of the running lights work great. The non-functional set is yellow w/ black stripe (yellow w/ red stripe being the working set).

I made a test light and put it across that fuse- shines brightly. Continuity test on the non-power side of the fuse to ground shows 0.9.
I've disconnected: front left running lights, trunk light, left license plate light, right tail lights, back right running light- no love.
I've jiggled the wire at all of the easy to access spots where the wire comes through metal: firewall, trunk, taillight- no change in the test light.

What am I missing? Does this indicate the short is in the wiring somewhere? If so, what is a sane way to approach finding it? Is it possible the wire has been accidentally attached directly to ground somewhere?

So far the best idea I've come up with is cutting/re-splicing the wire in various spots until I isolate the short to a certain stretch...

[azruss]

if you have a direct short, that wire will get hot in a hurry. of course, it will only get hot between the power source (fuse box) and the point of short.

[spider2081]

What year is the car??
On my 1981
At the fuse panel the fuse 8 (H) has 2 terminals with 2 yellow/black wires. The wires can be pulled off one at a time and that should eliminate some of the possible shorts. One wire feeds the dash lights, cigar lighter lamp and lights on indicator in the speedometer. The other wire feeds everything else
Have you looked at the wires in the trunk on the drivers side carefully. The wire harness kind of just sits there and there are some wires that may not be used in your car that could be the problem. You have to fold down the carpet to get a good look in there.

[MTMike]

As an update to this- I haven't made any real progress other than confirming that all endpoints are disconnected from the circuit. At this point I'm leaning towards running a new wire...

[focodave]

You need to start over again with a systematic approach, otherwise you could be chasing your tail endlessly and get frustrated very quickly.
You've got one thing going for you -- you know what circuit (running lights) is the bad one.
I would disconnect every running light (and anything else on that particular circuit -- including the fuse).
Also take all of the light bulbs out of the light assemblies you have disconnected.
Since we don't know what year car you have, it is difficult to speak in specifics so I will generalize.
Again, disconnect every single thing that is involved in that particular circuit.
You will find a lot more than just the running lights connected to the fuses that the running lights are connected to.
You need to look at some wiring diagrams for your car.
Then, using an ohmmeter -- connect the ohmmeter between the fuse terminal to ground.
Make sure the ignition is off when doing this. (in fact -- take the key out of the ignition to make sure it is off)
If you have continuity between the fuse block terminal and ground, then you have at least isolated the problem to the wires that are still plugged in.
If you have no continuity, then you need to plug one thing in at a time, until you find the one item that causes continuity between the fuse block hot terminal and ground.
Once you find the offending light assembly or other item in the circuit, you will at least know what wires to concentrate on either replacing or finding the short circuit in and fixing the short circuit.
I hope this explanation was not too basic or condescending. I don't know what your skill-sets are, so I have to assume you are looking for basic instructions.
Good luck with it and let us know what you discover.
Also, please tell us what year spider you have.