Tracing wire runs

I have a dome light in my front storage closet which does not work. I need light b/c this storage closet is where I keep a lot of my safety gear.

I pulled the dome fixture and found a wire run in the ceiling (black and blue/white, probably 10 gauge). The dome light was originally tapped off (in parallel) from this run using red wires. Someone (previous owner, not me!) cut the red wire from the blue/white side of the tap (see photo) and then ran a new black 14g wire from the light switch to another light switch far off on the other side of the boat. I have no idea why (that's boating !).

When I put my voltmeter between the black and blue/white source, there is no voltage. I have a Fluke Pro3000 tone tracer, which I tried, but the tracing tones seem to be everywhere in the ceiling and electrical closet.

I cannot see visually where the source wiring is coming from without tearing up the closet ceiling. I have searched my electrical closet for the same color (blue/white) and did not see it, but colors are not completely reliable as a new color can be spliced in anywhere.

Is there a good method for tracing the source wiring backwards to the electrical panel?

You have to do it with your tester and a long cable.

1.- set your tester to the "beep" position and test both poles.
2.- attach one of the poles to one probe.
3.- disconnect the cable to test from his position and attach the second probe.

4.- without tension (disconnect main switch) try point by point any connection in the main switch panel. Tray first cables of the same colour than the tested wire.

5.- if you have no beeps, it will mean that the subjected cable is interrupted somewhere...

If you lower that wood mount, you will see the direction the wires run. Find the wires that head towards the breaker panel and check for voltage wherever you can.

You say the black wire goes to another switch. Is there power to the light when you turn on that switch?

Sounds like power or ground was needed at either of the two lights when we bought the eagle there were three lights with no power and the wire ran thru the ceiling. So I ran wire from a light that worked to the light that did not. I hide the wire by routing out 1/2 round. That sounds like what was done. Does the other light work.

Tone chasing is only good if the wire is disconnected on both ends. If you have a harness that is dry it will work great. One ground with tone on it will run wild all over the boat.
Telephone Cable man here, chased tone for 30 years. Most likely post number 2 is your best bet.

High Wire: I did remove the wound mount, and there is only a 1 inch hole in the ceiling panel. I cannot see where the run goes.

Capt.Bill11: There is still no power to the light when closing the switch on the other light.

Mule: Exactly what I found. Tones everywhere. I will have to try cutting the wires in the loop and re-testing, as suggested by Alberto.

Phil Fill: Yes, the other light works and I could run a new hot and ground from the working light back to the fixture that is dead.

However, the reason for posting this thread is for me to try to learn how to trace any such wires, if I cannot visually see their origin. This is a common problem on older boats, and I suspect I will need this skill in other places on my boat. I can run new wires, but then I have old and new mixed in together, hot wires mixed with dead wires, more confusion later on. I was curious to know if the gurus have a way to "peak" at the wire runs and find out where they come from. A skill, no doubt, and the result of much experience...

If the Fox and Hound is not cutting it then you need to use a toning test meter and long wires with clips on the end as mentioned.

"the reason for posting this thread is for me to try to learn how to trace any such wires, if I cannot visually see their origin. This is a common problem on older boats,"

The same hassles exist on lots of brand new boats , thats why it usually takes 6+ months to outfit .

My technique is to purchase an ac hot wire finder from a box store.

Also purchase a small 12v vibrating bell .Toss the bell and use the unit to convert your boat DC to pulsating DC .

The wire finder does not know the difference,

Shut off ALL the boats juice and use a small 12v batt and the bell unit to power thev line you wish to trace.

When it stops indicating you have found the wire end.