1 Answer

Things You'll Need
12 volt test light
self powered test light

Instructions
1
Determine what type of short you are dealing with. There are three types of shorted circuits.
1. short to power
2. short to ground
3. short to another load circuit

2
I will use my 96 Pontiac Grand Am as the example, I had a ghost in my car. (or so I thought) The left front park lamp would glow anytime it wanted and just as mysteriously go back off. Find a wiring diagram and study it, find out where the connectors are for that circuit. Starting at the symptom circuit which was the left front park lamp, disconnect the bulb and check for power at the bulb. There is power when the lamp was on.

3
Find the next connector up the circuit, in my case it was next to the left fender. Disconnect the connector and check for power on the left park lamp circuit, there was none. I reconnected the connector and the lamp circuit was powered up again. This indicated a short to power between the lamp and the next connector.

4
I disconnected the connector at the left fender opening the circuit and stripped the tape from the outside of the wiring. Following the wiring from the connector toward the lamp I found a wire that had melted and shorted across several wires creating a short to power. I replaced all the damaged wires with new wires, soldered and taped for a water tight repair. The car has been working fine ever since!

5
The self powered test light is used to find shorts as well, you have to disconnect the wiring at both ends of the circuit and go from one wire to the next to see which wires are shorted together. The self powered test lamp will also find a short to ground, but make sure the load device is unhooked first.

Read more: How to Find a Short in Wiring | eHow.com http://www.ehow.com/how_4461401_short-wiring.html#ixzz2OOowXaCF