Originally Posted by overlander63
What he said. These things are notorious for bad grounds. Hook a test light up to a good ground, and touch the other end to the ground lug on the panel. If the light lights, you have a bad ground.
Hi Overlander63; The most effective and least time consuming troubleshooting of open circuits in DC is as you said, is use a test light.
However, there can be a hitch in some instances. Test light does not require much amperage to indicate a closed circuit, but in places as the distribution panel where amperage demand is high, partial open can drive you to having too many beers. The best way is as you said, check for continuity.
To check for open negative circuit place the test light clip on the positive battery terminal, and test each negative terminal. To check the positive wires reverse the process. This will identify the polarity of the tested wire, as well as any open circuits. The hitch may occur in case of corroded or weak connection where required amperage delivery across that connection is insufficient. The weak connection may provide enough amperage to light the test light, but you still may have a problem with high demand circuits. This is why it is easier to ensure that all connections on power supply side are solid and clean, on the battery and the distribution panel. Most of the time it is dirty or corroded terminals, rather than broken wire inside the skins that is a problem. That is the most prevalent scenario in the marine application. If the terminals are good and clean, only then we need to break out Ohmmeter to check the Resistance in the wire. Load tests on wires usually result in fire especially in unprotected circuits.
Problems in high amperage demand circuits lays most of times in bad connections. Thanks, "Boatdoc"