Circuit breaker tripping for interior cabin lites

[Loya]

The instant we try to turn on the main cabin lite switch on the master panel, it kicks off. So does this mean the problem is in the switch/circuit breaker. Or do I still have to go through the entire boat and check for bad switches on each lite.
The main switch doesn't stay on long enough to allow for checking of any interior lites.
I did try to switch the wires from the back of the cabin lites circuit over to another circuit that I knew was functioning properly,(the loran circuit) and the cabin lites wires caused that circuit to trip off as soon as I tried to switch it on. If i can fix this with a $27.00 circuit I would be so happy.
Has anyone else had this kind of electric trouble.
The boat is a 1984 Hunter 34'. It is a great boat and a real family favorite, it would be nice of I could get the interior lites and fans working again so we could enjoy the rest of our summer.
thanks for any input.
JL

 

[Stu Jackson]

Uhm, didn't you just ask this question and have it answered?

See: http://www.sailboatowners.com/forums/pviewall.tpl?uid=73200280089&sku=2008215001521.27&forumabr=as&fno=21

 

[Chuck Creel]

breaker tripping

You obviously have a short somewhere in the circuit. You lights are conncted in parralel " daisy chained from one to the other in line." TAke down ALL your interior lights and turn on the breaker. Hopefully its just a screw thats shorting them out after the years. Have you had any leaks lately? water will short it out if the wires are in water somewhere.

 

[Maine Sail]

It really..

sounds like it could be a dead short too. While it's possible it could be a breaker this type of failure is less often to happen than a failed fixture or a chafed spot in a wire causing a dead short.

To trouble shoot the entire circuit:

1) Use a DVM (digital volt meter) on the Ohm setting (resistance) connect the black lead of the DVM to the lighting circuits 12V ground or the system 12v ground. (Hint; first touch the black and red leads of the DVM together so you know what a completed circuit looks like on your meter.)

2) Turn of all lighting or electrical devices in the circuit.

3) Disconnect the read wire from the back of the breaker in question and touch it to the red wire of the DVM. If you complete the circuit there is a short somewhere. Often times with lights that can "spin" or be "aimed" people over spin them and snap a lead off. It can then ground out.

 

[GuyT]

To check for a short...

try this:

Put a 12V bulb in parallel with the "off" main circuit breaker. If your wirring is a dead short, that bulb will illuminate.

If that test bulb across your "off" main breaker is illuminated, you can use it as your test light.
Go to each lighting fixture individually and jiggle the on/off switch.
If you have no luck toggling each swith on/off , remove the bulbs one at a time.
Still no luck - remove the fixtures one at a time - hopefully you won't have to go that far
Once you find your short circuit and clear it, the test bulb across your "off" Main breaker will go off.

No DVM necessary.

 

[Captphil24]

Gemini is right on.

Gemini's solution to finding is the best I have ever seen. 10 points.