general guide for chasing shorts?

Electronic shorts in a car. I'm curious where the shorts most commonly occur. For example, I had

an internal short in my ignition coil that was blowing fuses. Also, instructions on how to test wires , connectors, etc..to chase down the short.  Voltage drop vs resistance? Can you stab the multimeter probes through the

plastic insulation of wire?

I'll give my take as well since I basically spend my entire life chasing down shorts.

First off there really is no particular place where shorts occur most..basically they can occur anywhere..any time..for many reasons. In my industry it is common to see wires pinched under seats..or wires hanging against exhaust manifolds. Sometimes a screw is put through a wire as well.

Some devices can internally short...motors..speakers and a host of other components. By simply disconnecting the suspect component..then checking the wires for a short with a meter can quickly tell you which one is the culprit.

As far as voltage drop vs.resistance.. Voltage drop is a sympton of resistance...that about sums up the relationship for this topic. A dead short to ground (zero resistance)causes blown fuses..and in the worst case burned up stuff and/ or wires.

Everything posted by Hymer is great advice so I see no need to add anything else. If you have any other questions feel free to ask away.

Divide and conquer.

Thats really all you can do.

It's also important to identify exactly when the problem is occuring, especially if there are several components on one fuse.

For instance, if you keep blowing a headlight fuse when you turn your headlights on check to see if the fuse blows when you only turn the parking lights on (if they are on the same fuse, which most are not, but its the only example I could think of).

Also, as said above, unplug as many things as possible and keep testing with a meter (I don't recomend using small fuses to test as they are somewhat costly, especially if you use 25 of them!)  If you know you have a short to ground you can measure the fuse holder output side to ground and determine when the short has been fixed.

While on the topic...I have seen a few times a problem with a short come down to this.......a dime fell into the cigarette lighter socket. On some American vehicles you will lose the interior lights...radio..clock..and perhaps more. Also have seen it cause in a few caddilacs all kinds of crazy feedback with gauges and lights doing weird stuff.

In many imports you lose the radio and sometimes other accesories as well .

By knowing all the circuits on the blown fuse (read the owners manuals) I did a visual inspection of each device until I saw the coin. Now I know by experience to check in the lighter socket first.

Another example of many in the world of 12v automotive electronics. Just thought I'd share.