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  #1  
Old 06-21-2011
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Puzzling electrical problem

All the 12 volt electrical circuits on my C&C 35 Landfall just failed. The engine still starts, and the refrig still works, but all the circuits for the lights, instruments, bilge pump, sump pump, stereo, vhf, etc., are dead.

Since the engine starts and refrig works, the batteries must be ok. Also, the battery charger must be ok as well. There doesn't appear to be a main breaker for the entire 12 volt system. Each 12 volt circuit has it's own breaker. Does anyone have an idea why all those circuits might go bad at once?

I'm currently away from my home slip, and my "electrical expert," but would like to fix it, if possible, so I don't get caught out after dark without lights, or have to anchor in the dark. Thanks for any help.
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Check the connections between the house batteries and the panel.

And, especially, check out the GROUND connections.

I had a client with the same problem...turned out to be a corroded household-type fuse holder which fed the panel.

Another client had a bad main switch (the 1-2-BOTH-OFF variety). So badly deteriorated that no amperage was getting thru.

Check ALL the connections; make sure they are clean and tight.

Bill

Last edited by btrayfors; 06-21-2011 at 03:27 PM.
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I would think there must be a main fuse or breaker that supplies the rest of the 12V system. On our boat, it is a larger fuse behind the panel, but there is no switch on the panel itself. I wish I had a photo -- would be much easier to explain.

P.S. I like Bill's suggestion of checking the 1-2-Both switch.
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P.S.

If you are not experienced with electricity...and it seems you may not be...then be sure to DISCONNECT any shorepower, inverter and/or generator.

Then, with just 12-volt power, you can poke around at ease without fear of electrocution.

And, just because you find one problem doesn't mean there aren't more. Be as thorough as you can.

Bill

Last edited by btrayfors; 06-21-2011 at 03:33 PM.
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Do you have voltage at the breakers in the panel? You might have an inline fuse in the battery cables. You might have fault in the negative bus if all failed together as probably all negatives go to the same bus? Check voltage between the positive behind one of the breakers and negative at the battery terminal.
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12 volt systems can drive you crazy!. Start by disconnecting from shore power and any generator as noted above. Begin at the alternator or generator and trace the circuit forward. Some where you should find either a fuse or a breaker. Also consider disconnecting one piece of electronics at a time and seeing if the remainder come back on. Lastly, although this is time consuming, when you have a week of free time, trace every wire and remove any that go nowhere. Old wiring can fray and short out. The only remedy for that is complete removal of all old/unused wiring. Oh, as noted above, make sure your ground connections are not corroded. Easy as pie!
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Fridges often have their own feed, separate from the main panel buss' as does the engine..

Another possibility is you've got a loose/corroded connection behind the panel, on either the positive or ground buss bars
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Some good advice in the previous posts...

For safety's sake, kill any 110V power coming aboard...unplug SP, shutdown generator.

Your fridge is likely on its own circuit, since it is a relatively large load.

Other 12V circuits through your distribution panel are likely powered on the positive side from a single high capacity wire from the battery selector switch. House battery positive leads (normally red) are individually connected to the battery selector switch. If you have no power from either house battery in any switch position, and if the problem is in the positive side of the wiring, it is either the switch or the wire from the switch to your distribution center (it is unlikely that that wire is fused...usually only the individual loads are breakered/fused.

The negative side of the power distribution to these loads (normally black wires) is generally wired to a terminal block outside the panel on a bulkhead somewhere. The negative leads from loads go to this terminal block which is in turn connected via a large ground wire to ship's ground. If this large ground wire fails, all the loads off the ground terminal block will fail since there is no return circuit for the power to the batteries.

So, check battery voltage using installed voltmeter with the battery selector switched to 1, 2, and both, or handheld voltmeter at the batteries. If voltage is good at the installed voltmeter, and the voltmeter is at the distribution panel, open the distribution panel and check for voltage at individual loads' breakers. If you have voltage, the problem is on the negative side. If there is no voltage at the panel, gain access to the back of the battery selector switch, identify the output terminals for each position, and check voltage. If there is no voltage, the switch is bad. If there is voltage, check the voltage at the panel breakers, and if there is no voltage there, the main lead to the panel is likely at fault (open).

If there is voltage at the distribution panel breakers, your problem is on the negative side. Check connections from the battery negative to your house ground, and from the house ground (could be at the engine) to the negative terminal board. Use an ohm meter to check electrical continuity of the circuit, as well as visually inspect.

Wiggle wires a bit looking for broken wires, look for corrosion (green from copper wires or white at battery connections) and clean any dirty, corroded connections.

Hope this helps. Good luck.
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Old 06-22-2011
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Quote:
Originally Posted by fryewe View Post
Wiggle wires a bit looking for broken wires, look for corrosion (green from copper wires or white at battery connections) and clean any dirty, corroded connections.

Hope this helps. Good luck.
I know just enough about electricity to not wet my finger and touch a wire to see if it's hot, but I really don't know how boats are wired, so for now, I'll follow the above advice. All the above suggestions have given me a good idea of which wires to look at for breaks and corrosion, and which to wiggle, and maybe I'll find it. If not, I'll give the job to the electrician working at my marina, when I get back. Thanks for all the suggestions! I knew you guys would point me in the right direction.
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Great! A good plan.

JUST BE SURE TO DISCONNECT SHOREPOWER (AND ANY INVERTER OR GENERATOR) BEFORE YOU TOUCH ANYTHING.

It ain't rocket science. Don't be afraid to loosen a screw or nut and look carefully at the connection. Clean up any which look suspect with light sandpaper. Wiggle all connections to be sure they are tight. You may be surprised at how many are not.

But, first of all, check the ground connections. Make sure they're clean and tight.

Then, check the fuses and/or breakers in the line between the batteries and the panel.

Then, check behind the panel.

It's a good idea when poking around to take off rings and watches...you don't want to inadvertently cause a short circuit between anything positive and anything negative. Be especially careful around the batteries and their heavy cables. A short here caused, e.g., by a screwdriver or wrench across the positive and negative poles or leads can be catastrophic...could cause a fire or the batteries to explode.

Other than the danger of causing a short circuit, with the shorepower/inverter/generator off you can poke around and not be worried about killing yourself or burning up the boat.

Good luck. Let us know what you find.

My bet is it's a bad ground connection or a fuse.

Bill
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