Electric short? need help, want to sail - SailNet Community
 
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post #1 of 9 Old 06-13-2009 Thread Starter
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Electric short? need help, want to sail

Last weekend, I noticed that my GPS and VHF kept shutting off intermittently. After some trouble shooting, I isolated it to cycling the bilge pump, either in manual mode or when raising the float switch in the bilge sump. When I cycle the bilge pump, house lights, VHF, stereo, etc. all go dark and come back on when bilge pump stops. Pulling all new cable for bilge pump is going to be a pain due to access. Is this the right approach or is there another problem I am not thinking of?

Thanks for any help!
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post #2 of 9 Old 06-13-2009
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Taht doesn't sound like a short, it sounds like a bad connection between the battery and the first device in the circuit that goes off. The bilge pump probably draws quite a bit of current. If the circuit has a bad connection, high resistance, then when the bilge pump turns on it pulls the voltage down. All you need to prove this is to put a voltmeter across the power leads on on of the lights that goes dark. You'll probably see the voltage drop from around 12 volts down to only a volt or two. Work your way back towards the battery. When you stop seeing the voltage drop you've just passed the bad connection!

Hope this helps.
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post #3 of 9 Old 06-13-2009 Thread Starter
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Gary,

Thanks. I'm still a bit confused. Each of the loads that shut off (VHF, GPS, etc.) are all on separate circuit breakers. Bilge pump is on independent circuit breaker. So, I'm not sure what you mean by the first device in the circuit since I believe the bilge pump is the only device on that circuit. Why would that circuit affect the GPS on a different circuit?

really appreciate your quick reply. Will be back on the boat tomorrow and would like to get the darn thing resolved.
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post #4 of 9 Old 06-13-2009
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Okay, that suggests the bad connection is between the battery and the circuit breakers. Easy to verify. measure the voltage on the battery side of the circuit breakers when the bilge pump is turned on. If it is real low then the bad connection has to be from there back to the battery.

If you drop me an email I will give you my cell phone number and I could walk you through it over the phone while you are at the boat. I am kind of Macgyver, and grew up in the electrical business, trouble shooting is what I do.
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post #5 of 9 Old 06-13-2009 Thread Starter
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Sent PM. Thank you so much, what you say makes sense now.
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post #6 of 9 Old 06-13-2009
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It could also be that the battery is shot. A bilge pump is going to be much less voltage sensitive than the electronics, and it is also going to draw more current then any single piece of electronics (in general).

So the pump kicks on loading the battery, and the voltage out of the battery drops, killing the electronics. So put your volt meter right on the battery and turn the pump on. Most likely the voltage will drop.

Next, disconnect everything but the pump. Repeat the test. If the voltage drops again, your battery is shot, or at least dead.

An easier test might be to turn the engine on (if you have one). Now your alternator is providing power. You should see 14 volts on the battery with the engine running. Kick the pump on, see what happens. If the electronics stay up and the voltage at the battery holds, replace the battery.

If you turn the engine on and do not see the voltage go to 14, you have a problem with the engine not charging the battery. This could be many things, which I won't list unless you report this as the problem.
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post #7 of 9 Old 06-13-2009 Thread Starter
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This is getting interesting. Your questions show that I did not provide enough information. When I first noted the problem (elex shutting down), I was running on engine (Westerbeke 27). Troubleshooting was done after returning to slip and shutting engine down. I'll check battery as suggested, but it sounds like could be fried alternator/voltage regulator as well as battery? A post from week before last had to do with not being able to start engine. Found an open in negative cable from battery bank to engine block. Had just replaced battery charger -- had an old NewMar charger (probably original to the boat). The old battery charger kept blowing fuses, and the fuse block would not seat well in the charger. But, on launching, everything worked fine. Problem only started two weeks after launch. Sounds like I've been chasing the wrong problem.
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post #8 of 9 Old 06-14-2009
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While the items are on different circuits, the ground is common. I think an iffy ground could cause this to happen.
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post #9 of 9 Old 06-14-2009
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Quote:
Originally Posted by 82Sabre34 View Post
... When I first noted the problem (elex shutting down), I was running on engine (Westerbeke 27). Troubleshooting was done after returning to slip and shutting engine down. I'll check battery as suggested, but it sounds like could be fried alternator/voltage regulator as well as battery? ... Found an open in negative cable from battery bank to engine block.
Well as someone else just said, check your ground to make sure it is solid. Last last season another boat owner here could not get his engine to start. The problem turned out to be that the ground cable was not well connected to its connector, so even though the connector was tight on the battery, the cable failed.

Start at the battery and work backwards. Make sure you see charging voltage or about 14 volts with the engine running. Do you have any battery switches or a battery combiner that could have failed? If so check those.

How many batteries do you have?

If the problem happens with the engine running AND you see 14 volts, then your charging circuit is working and as others have said you most likely have a bad cable (or maybe a bad switch) somewhere.

But somewhere, the voltage is dropping when your pump puts a load on your wiring. If it kills everything, check the ground and the positive to the fuse panel.
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