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  #11  
Old 04-24-2013
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Re: Short in lighting circuit affects radio?

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Originally Posted by hellosailor View Post
L-
It would take some brain-wracking to try to figure out the exact problem, but the bottom line is that those two circuits, which you think are separate, are in fact not separate. Somehow they've been wired together. Possibly at some time in the past someone added something or repaired something and said "I'll just connect it over here" and got the wiring crossed.
Certainly, the mast lights are separate from the running lights, as I re-wired the grounds on the mast lights myself (to eliminate unnecessary circuit length), and the hots are separate as they are individually switched, correct? Yet, the the mast lights were affected by cutting the ground on the Port running light.

Last edited by L124C; 04-24-2013 at 01:49 PM.
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  #12  
Old 04-24-2013
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Re: Short in lighting circuit affects radio?

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Originally Posted by hellosailor View Post
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Since the bow running lights are always turned on as a pair (or wired with the stern light, all three on one switch) there is no reason at all for them to be wired up separately. If the wiring is adequate, I'd suggest moving the both over to the side you know is isolated (Port side?) or putting them both on one new wiring run as well. If someone ran dedicated grounds all the way down the length of the boat to the bow lights, that could give enough voltage drop to cause voltage loops (aka ground loops, whatever) in other wiring, which again explains odd behavior in other circuits.
Interesting point, given that the bow running lights are also 3 feet from each other. It would have certainly been easier for them (probably the builder) to run a single circuit to the bow.
So, even given appropriate wire size for the length of the circuit in both methods, is it more efficient (in terms of voltage drop) to run both lights on the same supply/ground wire?

Last edited by L124C; 04-24-2013 at 02:49 PM.
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  #13  
Old 04-24-2013
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Re: Short in lighting circuit affects radio?

"So, even given appropriate wire size for the length of the circuit in both methods, is it more efficient (in terms of voltage drop) to run the same lights on the same circuit"
Well, IF the wire was chosen for the right voltage drop (same drop) it wouldn't make any difference whether they ran two circuits or one. It would be simpler, neater, probably cheaper and just "the right way to do it" to use one circuit. Could be that someone didn't have the right wire, so they ran two runs of lighter gauge wire. That's a perfectly adequate kludge--but still an odd one. Maybe someone said "the bow lights are awful dim, maybe if I run another wire..." who knows.
Sometimes it is just simpler to say "this isn't right, let's do it over from scratch" and move on.
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Old 04-25-2013
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Re: Short in lighting circuit affects radio?

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Originally Posted by hellosailor View Post
Sometimes it is just simpler to say "this isn't right, let's do it over from scratch" and move on.
Yeah... but I got a lot of "this ain't right" on this boat and only so much time. The running lights are plenty bright, so I'm going to go by the axiom "if it ain't broke, don't fix it"! I start one project and find three more! I have to tear myself away, and go to my job that pays!
Some of the wiring on this boat must be factory. Hard to believe what apparently passed in the 70's! The boat's built like a tank, but the wiring!
Still pondering the question in #11 though. Can't figure out why the Port bow and Stearn running lights still worked (both having separate grounds) with the Starboard light ground cut. Yet, it apparently created a ground fault loop for the rest of the lights.
Oh well...here's another axiom - Why ask why? Move on to the next project!

Last edited by L124C; 04-25-2013 at 02:11 PM.
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Old 05-16-2013
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Re: Short in lighting circuit affects radio?

I have a similar problem I am trying to track down. when I turn my lighting circuit breaker on the voltage meter pegs at the bottom. This does not seem to effect other circuits though? I first though the breaker was bad but I disconnected the lighting wires and it works fine.

I am guessing it is a bad ground. If so what are my options for tracking it down short of rewiring the circuit s the OP did?
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Old 05-16-2013
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Re: Short in lighting circuit affects radio?

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Originally Posted by cranki View Post
I have a similar problem I am trying to track down. when I turn my lighting circuit breaker on the voltage meter pegs at the bottom. This does not seem to effect other circuits though? I first though the breaker was bad but I disconnected the lighting wires and it works fine.

I am guessing it is a bad ground. If so what are my options for tracking it down short of rewiring the circuit s the OP did?
Look closely at the meter wiring. It's behaving as if the meter (-) is attached to lighting (+).

What do you mean by dis-connected the lighting wires. From where?
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Old 05-16-2013
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Re: Short in lighting circuit affects radio?

Not a "bad" ground, which usually means open, but that something on the lighting circuit is drawing way too much power and pulling down the batteries. Which might be weak if they are being pulled down that way.

So you need to load test your batteries, then use an ammeter or voltmeter to test the lighting circuit. You can start by testing the amperage it pulls when "no" lights are on or "all" lights are on and if that doesn't match the power rating of the bulbs, split the circuit in half, measure each half, keep dividing it down until you find the bad section.
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Re: Short in lighting circuit affects radio?

Batteries seem fine and are connected to a 3 stage charger. There are actually 2 lighting circuit and one of them behaves this way. When I say I disconnected the circuit I removed the wires from the breaker to test the barker. I also hel the words onto the other lighting circuit breaker with the same effect of immediate and drastic voltage drop. The rest of the 12 volt system works normally, just the one lighting circuit. I don;t know if this will help but the problem started suddenly when a bulb burned out in the head. DO not know its something there cause this or if that was a symptom or if coincidence?
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Old 05-16-2013
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Re: Short in lighting circuit affects radio?

I was thinking that when you said no effect on the other circuits you meant that the short (turning on the bad light circuit) doesn't affect them. Is that true? Or did the lights dim when you held the bad lighting circuit onto the good circuit?

The question here is whether voltage of the whole panel is actually dropping or whether the meter is just being tricked by a miswire. Now I think it's more likely the former (as Hello was getting at), although I'm surprised the breaker didn't trip in that case.

How big are the breakers on the lighting circuit here?

If it really has anything to do with a light burning out then I'd look closely at that light fixture. Something beyond the bulb may have failed and is creating a short there.
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  #20  
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Re: Short in lighting circuit affects radio?

The bad light circuit does not seem to effect voltage on other circuits. I just touched it to a functioning circuit and saw no dimming of the lights.
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