DC short?

[adamkat22]

Im' slowly trying to fix and/or redo the wiring in a 70's houseboat I just got. Looks like someone did at least one round of DIY wiring in its lifetime..which makes familiarizing myself with it even harder for me.

There are quite a few loose/cut wires in the walls/ceiling and right now I'm just trying to trace them so I can see where they were coming from. I'm using a continuity meter. Some of the wires I am getting continuity on both + and - of several circuits. I don't understand why this would happen. Does it mean that I have a short somewhere or is this normal?

Sort of a vague question but thanks for any thoughts.

 

[gm280]

If you can attach a sounder system to the end of the wires, you could trace them all the way without tearing anything open. I personally would remove every wire that wasn't actually being used to make future efforts less complicated. I don't like cluttered wiring on anything. A sounder system transmits a frequency on the wire and you hold a receiver in your hand and slide it against the walls to see where the wires go. They sell such things at the home improvement stores. JMHO!

 

[adamkat22]

The ceiling had to come down (moldy) and the walls already had openings with some huge wire chases...so it's fairly easy to see most wires. But yes 'removing the clutter' is exactly what I"m trying to do. When I find a cut wire somewhere I'm trying to see where it lands on the fuse block so I can get rid of it. I just don't understand what is going on when I have a cut wire in a wall and I am finding continuity with it at several different locations on the fuse block as well as at several places on the negative bar...

 

[mf70]

It can be very confusing, as you are discovering, to try and trace out an existing network of connections. Add to that the probable incompetence of at least SOME of the intervening changes, and it will take some extended clear thinking to get rid of the tangle.

I would do two things: 1) Remove (and tag) all wires to the fuse block before attempting to trace a line. 2) draw a diagram of what you know. You may need to re-draw it as you learn more about what is in there.

If there is continuity, electricity can flow between the points tested. However, it may not be flowing in the path you are imagining.

 

[Grandad]

Hi Adam. You will see continuity between many points of circuits that are not isolated. Remember that all of the circuits are connected together if they all come from the same voltage source. It's obvious that if all the negatives connect together that you'll find continuity between all the negative wires, though each may be for different loads. What is often overlooked is that wherever a load is connected to both positive and negative supply wires, you will see continuity between positive and negative through the resistive value of the load.

Depending upon the sophistication of your test meter and your knowledge of the correct selector range for ohms, you may see a connection between every connected load through both the positive and negative wires. For example, assuming that all switches are turned on, you'll see continuity between the positive of your navigation lights and the positive of your bilge pump because both of these loads are connected together at the negative terminal block and your test current will connect via that common point. - Grandad