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Old 02-16-2018, 12:41 PM   #1
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Electrical Issue

Here is the issue Iím dealing with.

Background: I have two panels in the pilothouse. One is the main panel, and it has a 65 amp breaker that supplies the 12V electronics panel under the helm. The voltmeter on the helm always reads a little lower than the actual alternator/battery voltage. And since we have owned the boat, the voltmeter always jumps around when we use any of the electronics. For example, the voltmeter will dip below 12V whenever the autopilot moves the rudder. I thought this was normal because it was described in the operating manual by the original owner.

New issue: Twice now the electronic panel has gone dark. Everything turns off, but the engine remains running. The first time this happened, it came back on its own after about 15 seconds. The second time we had just anchored. When I came back to the helm to shut down, it was dark. But I couldnít stop the engine because the start/stop switches were dead. I had to open and close the main pilothouse panel breaker to get the electronics panel to come back on.

What I have done so far: I checked the main breaker. Nothing loose. And it gets its power from a buss that has other things coming off it that are not effected.

I checked the two grounds that come off of the electronics panel. They looked OK...not corroded or loose. One did use two washers because the ring terminal was a little bigger than the post.

Cleaning the grounds and reattaching them did not help. Still have the problem.

Looking for help from the forum or an electrician.

Thanks, Mike
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Old 02-16-2018, 12:58 PM   #2
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Use your meter and check the battery voltage at the source, then use the same meter to check the voltage at the panel, then meter the voltage at some of your services and compare. That should give you an idea where the wiring is deficient. Pay particular attention to battery selector switches, they are failure-prone.

Cut the ring terminal off and crimp the correct size. Important.
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Old 02-16-2018, 01:05 PM   #3
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Some bad connection somewhere I would assume. Worrisome, in that a poor connection can build up heat.

If the whole panel is going dark then there are only a few connections that would affect the whole panel. The idea to check the switches is a good one.
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Old 02-16-2018, 01:28 PM   #4
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The panel having lower voltage than the batteries usually indicates that the supply wiring is too small. When the autopilot moves the rudder and the voltmeter drops would make me suspicious of small wiring. As has been suggested I would check all connections. Where are the washers you mentioned. They should not be between the connectors and the bus bars as they will cause a voltage drop. If you have a non contact thermometer you can check the connections and see if any is running hotter that the others. You can measure the run from the batteries to the panel and back to the batteries to check what size wire you need to carry the 65 amps with a 3% voltage drop. As to the complete loss of power and then it comes back on its own, I would suspect a loose connection. If you have time while it is off, I would put a volt meter on the various connections and see where you loose the voltage.
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Old 02-16-2018, 03:55 PM   #5
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So this afternoon my SmartGuage was showing 12.65V and the helm panel was showing 12.32. I canít figure out how to measure the voltage at the breaker because I donít see a ground in or near that panel.

I assume the wire coming off the breaker should go directly to the helm panel. But the helm panel has two sides with a separate positive wire for each side. But I donít see (as of yet) where the single wire coming from the breaker splits to two wires going to the helm panel. Iím wondering if that connection could be my problem.
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Old 02-16-2018, 04:16 PM   #6
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Originally Posted by MikeM View Post
So this afternoon my SmartGuage was showing 12.65V and the helm panel was showing 12.32. I can’t figure out how to measure the voltage at the breaker because I don’t see a ground in or near that panel.

I assume the wire coming off the breaker should go directly to the helm panel. But the helm panel has two sides with a separate positive wire for each side. But I don’t see (as of yet) where the single wire coming from the breaker splits to two wires going to the helm panel. I’m wondering if that connection could be my problem.
Hey Mike,


It sounds like you are on the right path. 12.65Vdc to 12.32Vdc is negligible. That could be a voltage drop of the wiring.

You can check the voltage at the circuit breaker (C/B) by placing your red lead on the breaker and then the black on any negative (black wire connection.

Having intermittent issues are a PIA as they are sometimes hard to find. So let eliminate the obvious. Turn off the helm panel. Start with the breaker and start tugging on the wires, checking for a loose connection and corrosion. Follow the main wire to the split tug and check. Keep doing this until you have covered the entire panel.

It sounds like your issue is a loose and/or a corroded wire or a switch (battery switch maybe). Clean everything. This will take time. While you are at it, mark the wires so you know where they go for future reference.

Good Luck. Probably something simple.
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Old 02-16-2018, 04:24 PM   #7
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Mike: I just checked the voltages on Hobo. The pilot house voltage was taken at the key and the instrument cluster.
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Old 02-16-2018, 06:05 PM   #8
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Thanks everyone.

Hereís the test I did of the circuit breaker at the suggestion of Steve Sipe.

I put one voltmeter probe on the in terminal and one on the out. I got a reading of 17V. BTW, it is a 50 amp breaker, not a 65.

I turned a bunch of stuff on on the helm panel before I tested the breaker. As I was testing I noticed that the breaker was very hot...much hotter than the surrounding breakers.

So I think I have a bad breaker.

Thanks, Mike
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Old 02-16-2018, 07:12 PM   #9
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If the breaker is that much hotter than the rest of the breakers, change it out. Breakers are cheap and it may save you lots of time troubleshooting. I would still give your electrical system a good looking over. It is amazing what some PO may have done to it. Also put a screwdriver on each connection and make sure it is tight. Give all the butt connectors a tug, if they come apart it is good to know now and redo them with a proper crimp.
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Old 02-17-2018, 01:28 AM   #10
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17 volts? Is that a typo? Way too high for a (nominal) 12 v system.
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Old 02-17-2018, 08:08 AM   #11
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17 volts? Is that a typo? Way too high for a (nominal) 12 v system.


Now that you say that, it does seem weird. The number changed depending on what I turned on on the helm sub-panel. I checked it again this morning. At first it read almost 0, but then I realized there was nothing turned on. So I turned a few high draw items on one at a time, and the number went up correspondingly. I didnít get above 6V because I only turned a few things on.

A friend suggested I jumper out the breaker to see if I was still getting the voltage loss at the sub-panel. When I did that, the voltage went right up to what the Smartguage was showing at the battery. I assume thatís another indicator that the breaker is bad.
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Old 02-17-2018, 09:19 AM   #12
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Be sure and check your grounds.
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Old 02-17-2018, 11:03 AM   #13
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Are you sure it's not reading .6v rather than 6v?

But I agree with others that if the breaker is hot, start by replacing that. Even if that's not the only problem, you need to clear it before tracking down the next. A bad breaker would also be consistent with your with your whole panel going dark.

And as you work through this, keep in mind that the crimp connection between the wire and wire end terminal can fail too, and be much harder to find. Turning on a bunch of loads then checking methodically with a thermal gun, held as close to the target as possible, can go a long way to showing high resistance (hot) connections.
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Old 02-17-2018, 12:45 PM   #14
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You don't necessarily need a nearby ground to meter. You can put one probe on breaker input and one on breaker output, then read volt drop across the two. A good breaker with a few amps going through it will be in the tens of millivolts. More than a volt, crappy breaker.

Same technique can be used on any lead or connection. It is the way to find volt drops. Can also be used on negative path.
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Old 02-17-2018, 03:03 PM   #15
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Quote:
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The panel having lower voltage than the batteries usually indicates that the supply wiring is too small. When the autopilot moves the rudder and the voltmeter drops would make me suspicious of small wiring. As has been suggested I would check all connections. Where are the washers you mentioned. They should not be between the connectors and the bus bars as they will cause a voltage drop. If you have a non contact thermometer you can check the connections and see if any is running hotter that the others. You can measure the run from the batteries to the panel and back to the batteries to check what size wire you need to carry the 65 amps with a 3% voltage drop. As to the complete loss of power and then it comes back on its own, I would suspect a loose connection. If you have time while it is off, I would put a volt meter on the various connections and see where you loose the voltage.
ditto - he nailed it.
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Old 02-17-2018, 05:22 PM   #16
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Thanks everyone.

Hereís the test I did of the circuit breaker at the suggestion of Steve Sipe.

I put one voltmeter probe on the in terminal and one on the out. I got a reading of 17V. BTW, it is a 50 amp breaker, not a 65.

I turned a bunch of stuff on on the helm panel before I tested the breaker. As I was testing I noticed that the breaker was very hot...much hotter than the surrounding breakers.

So I think I have a bad breaker.

Thanks, Mike

You definitely have a BAD breaker. unless you clipped to one/two of the wire eyes and that was dirty. Yet, 17V or even 2 volts would be a BAD sign.
At full load there should not be more than a few millivolts of loss.
Change the breaker and ensure the wire terminals are clean, tight and properly crimped.
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Old 02-17-2018, 06:51 PM   #17
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You definitely have a BAD breaker. unless you clipped to one/two of the wire eyes and that was dirty. Yet, 17V or even 2 volts would be a BAD sign.

At full load there should not be more than a few millivolts of loss.

Change the breaker and ensure the wire terminals are clean, tight and properly crimped.

He has to have been reading his meter wrong. No way to get 17V in a 12V system. It may have been 1.7, and clearly a problem. Or it might have been 17mv and not a problem. But heating of the breaker does suggest a breaker problem, so my money is still on that as the problem.
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Old 02-17-2018, 07:13 PM   #18
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One is the main panel, and it has a 65 amp breaker that supplies the 12V electronics panel under the helm.
I can't imagine why there would be a 65 amp circuit breaker for anything but a thruster or windlass. I would expect more on the order of a 20 amp breaker.

If you have a circuit breaker that's getting hot, it is defective, whatever the rating.
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Old 02-17-2018, 07:24 PM   #19
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He is referring to the main DC breaker. I just installed a new electrical panel and my main breaker is 100 amps. This breaker supplies power for all the reat of the breakers in the panel.
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Old 02-17-2018, 11:41 PM   #20
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My Solo/Selene panel is set up with a 2 pole 50A breaker on the DC main. The poles are parallel connected so it's effectively a 100A breaker. The handles are also tied so if one trips, they both trip. Mike's 50A breaker is either a main or feeding a sub-panel. Either way, voltage drops as Ski pointed out, should be minimal, if measurable. A reading in more than 10ths is cause for further investigation. In regards to the 17V reading, it's not possible on a 12V system, more likely a misread decimal point or erroneous meter setting.

As far as using a DMM for troubleshooting, Ski covered the basics. It's a common method for diagnostic service work, but it can be counterintuitive to the casual troubleshooter since a zero reading indicates 'no problem'. Remember, that a meter reads voltage, or potential. Potential is essentially difference so we don't necessarily need to measure from ground to positive to get a meaningful reading. A closed switch should offer little or no resistance by design, so reading across a switch, breaker, relay, any switching device should see no potential, e.g. '0' volts = normal. This concept also applies to connections where there should be no resistance. The method of starting at a main connection and stepping along the energized circuit path can be helpful in locating problems. Any reading other than zero is a flag, and it points directly to the point where the non-zero reading appears. The higher the reading, the more significant the problem. The stepping method can, as Ski noted, be used on either side of the circuit from the dividing lines. Dividing lines being the potential source, e.g (+) (-) of the battery, charger, or power source; the other dividing line would be the load. Just another tool in the DX toolbag.
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