Navigation Lighting Circuit Conductor is Hot

Electrical and electronic topics for small boats
Dauntless
Posts: 29
Joined: Sun Aug 09, 2020 1:52 pm

Navigation Lighting Circuit Conductor is Hot

Postby Dauntless » Tue Aug 25, 2020 5:09 pm

[On a ] 2006 Dauntless 180 [the sidelight lantern or lanterns does/do] not [illuminate].

[The battery negative circuit conductor] is good.

[The battery power positive switched branch circuit for navigation lighting] wire is hot from the switch all the way until it disappears down below the console. This conductor appears to go aft in the wire harness, but I can’t find it anywhere until the [the lamp or lantern for the sidelights].

Looks like the wires go to the port [sidelight lamp] and then another wire from there to the starboard [sidelight lamp].

I pulled a little to see if I might just pull a new wire but it feels anchored.

Give me ideas.

jimh
Posts: 11672
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Navigation Lighting Circuit Conductor is Hot

Postby jimh » Tue Aug 25, 2020 7:42 pm

Have you recently installed any screw fasteners in the hull or topsides?

Dauntless
Posts: 29
Joined: Sun Aug 09, 2020 1:52 pm

Re: Navigation Lighting Circuit Conductor is Hot

Postby Dauntless » Tue Aug 25, 2020 9:49 pm

Just bought the boat but I don’t see anything that really doesn’t look original.

jimh
Posts: 11672
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Navigation Lighting Circuit Conductor is Hot

Postby jimh » Tue Aug 25, 2020 11:02 pm

If the circuit that is supposed to illuminate the navigation lighting does not illuminate those lamps, but the conductor feeding current to the lamps becomes hot, there is a short circuit. Make a close visual inspection of the circuit and find the short.

jimh
Posts: 11672
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Navigation Lighting Circuit Conductor is Hot

Postby jimh » Wed Aug 26, 2020 2:08 pm

I should explain about my question regarding installing a screw fastener. The wiring used for the navigation lamps is often a flat two-pair cable (sometimes known as zip cord because you can "unzipper" the two conductors easily into single conductors). This wiring is typically concealed below the rub rail on a Boston Whaler boat.

If someone installs a screw fastener near the flat two-conductor cable--and this is very likely to occur if the rub rail has been replaced and screws were used instead of rivets--there is a chance, albeit a small chance but I have seen it happen, that the screw will be placed so its goes exactly between the two conductors of the zip cord, screws right through them, and in the process creates a perfect short circuit.

I am able to tell you this can happen because I discovered this myself when helping a boating friend try to figure out why a lamp in the cabin of his boat stopped working and the fuse for the circuit always blew. He had recently added some decoration to the bulkhead and used a screw to secure it. The wiring for the lamp was concealed in the bulkhead, and his screw fastener when exactly through the center, shorting both wires together. It took over an hour or two for me to figure this out and find the short.

jimh
Posts: 11672
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Navigation Lighting Circuit Conductor is Hot

Postby jimh » Wed Aug 26, 2020 2:12 pm

I cannot tell you how to find a short circuit except by very close and careful visual examination of the wiring, all the way from the source of power toward the lamps. If the wiring gets hot that means there is a current flowing in the circuit but not reaching the lamps.

Also, a short circuit should blow the fuse. What sort of fuse rating in Amperes is protecting this circuit? For navigation lamps, I would expect that a 5-Ampere fuse would be plenty. A 5-Ampere fuse ought to open if there is enough current to cause the wiring to heat up. Check the fuse value. Perhaps some prior person thought, "Heck, just put in a bigger fuse to stop that 5-Ampere fuse from blowing all the time." Boat owners are often very awful electricians. Even boat mechanics--emphasis on mechanical--are often awful electricians.

Dauntless
Posts: 29
Joined: Sun Aug 09, 2020 1:52 pm

Re: Navigation Lighting Circuit Conductor is Hot

Postby Dauntless » Wed Aug 26, 2020 8:21 pm

Power comes from a breaker panel and goes to the switch. Then the hot wire runs across and down the console disappearing below the deck in a bundle of wiring. There is no short. When the switch is off there is no power. When the switch is on the wire has power as shown by a lamp tester. I haven’t been able to see the wire anywhere else until I expose it at the port nav light at which point there is no voltage.

I can’t figure out how to find where the wire is broken because it is all below deck. It is a gray wire. I hoped it went to the stern and then up the side but I can’t find it there. It must split off the main wiring loom somewhere below the deck that is unaccessible. And it seems to be tethered because it has no slack to pull.

So it seems there is no way to repair it or to run a new wire.

Dauntless
Posts: 29
Joined: Sun Aug 09, 2020 1:52 pm

Re: Navigation Lighting Circuit Conductor is Hot

Postby Dauntless » Wed Aug 26, 2020 8:23 pm

When I said “hot” I meant it had voltage not that the temperature felt hot.