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Old 13-11-2014, 21:21   #16
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Re: Low voltage reading on turned off circuit.

Don't know, but likely not induction. Is your bilge pump connected directly to battery like many of us do? Might be 'leakage' of 12v from failing bilge wire.

I'll try disconnecting EVERYTHING from the + battery terminal and re measuring to see if you still see 5.5v. Hopefully not. If not try reconnecting whatever was connected to the + terminal one at a time/ remeasure each time.

If you still don't see source/ try flipping each circuit breaker off one at a time/ remeasure after each.

If you have a dual power AC/DC refrig... or any dual power AC/DC device that auto-switches between AC and DC depending on which is available... with AC still to the boat and 12v main switch off... the AC/ DC dual power device may have switched to AC, which in some designs powers an internal power supply that still powers the device... maybe that's where your remaining voltage is coming from. Easy test to see if your backing up right tree is to also switch off the AC power to boat as well and remeasure.

5.5v DC is an unusual voltage in marine world... but not to modern electronics. All recent iPhones/ Pads/ Samsung/... and most modern 'wall wart' and USB chargers for modern electronics are all on the new 5.5v standard. Seems interesting that your phantom voltage is the same as this increasingly common gadget voltage. Might you have any 12v cigarette socket-to-USB charger and iPhone/ some device still connected to your now off/ floating 12v line that one of these devices might be improperly back feeding 5.5v back into your switched off 12v circuit? Wish I was there... like interesting troubleshooting/ brain teasers like this. There is always a logical explanation.

When you find cause, please post it so we can all learn from your interesting electrical issue.


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Old 14-11-2014, 12:46   #17
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Re: Low voltage reading on turned off circuit.

"5.5v DC is an unusual voltage in marine world... but ... most modern 'wall wart' and USB chargers for modern electronics are all on the new 5.5v standard. "


Nope. There's no 5.5V standard. The USB standard is 5.0, and internal computer components like drives also run on 5.0 volts for many years. 5.5 would exceed the tolerance for all of those.
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Old 14-11-2014, 18:38   #18
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Re: Low voltage reading on turned off circuit.

I'm waiting for the OP to come back and post his findings.
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Old 14-11-2014, 18:52   #19
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Re: Low voltage reading on turned off circuit.

I still think he is suffering from two wires, neg. side, making contact with each other and corrosion to the bus. He is reading the 5.5 through what ever the other wire goes to. Voltage does not just appear.

Wish it did, my power bill would be less.
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Old 14-11-2014, 18:59   #20
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Re: Low voltage reading on turned off circuit.

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I still think he is suffering from two wires, neg. side, making contact with each other and corrosion to the bus. He is reading the 5.5 through what ever the other wire goes to. Voltage does not just appear.
With a very sensitive digital voltmeter used incorrectly, voltage can seem to appear. Put any sort of load on it and the voltage drops to zero.
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Old 14-11-2014, 19:06   #21
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Re: Low voltage reading on turned off circuit.

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Originally Posted by rwidman View Post
With a very sensitive digital voltmeter used incorrectly, voltage can seem to appear. Put any sort of load on it and the voltage drops to zero.
I'll bet an old analog would do the same? Hope he jiggles those neg. leads.
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Old 14-11-2014, 19:11   #22
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Re: Low voltage reading on turned off circuit.

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I'll bet an old analog would do the same? Hope he jiggles those neg. leads.
Most of the old analog meters (except the best bench models) will load the circuit enough to short out any stray voltage. I was an electronic technician for most of my career and have used meters many times. I was around when all we had were analog meters and I worked through the change to mostly digital.

All we are doing is speculating until the OP comes back and tells us if he figured it out.
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Old 14-11-2014, 19:14   #23
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Re: Low voltage reading on turned off circuit.

Hell, you and I must just be across the creek from each other? Or is it crick. I'm in MP we may even know some of the same people?
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Old 14-11-2014, 19:28   #24
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Re: Low voltage reading on turned off circuit.

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Hell, you and I must just be across the creek from each other? Or is it crick. I'm in MP we may even know some of the same people?
Sorry to the thread. I thought I was sending a private message.

Probably to much grog. And a rough day with plumbing provider to the house.
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Old 14-11-2014, 19:28   #25
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Re: Low voltage reading on turned off circuit.

To "load" the circuit you could put your first two fingers (right hand ot left, not right and left) across the terminals. That would "load" the circuit.

This might be bad advice for the novice. And is probaly callous in my approach. So if electricity makes you nervous, or there is ANY chance of 110VAC being on your boat, don't do it.

(I stood next to an engineer when he grabbed a 440 bus thinking it was off. His rubber soles saved him, but scared the stuffing outta me. "Oh, that's hot." Says he!)

I have a love/hate relationship with digital meters for these kind of reasons. Auto scale - hate it. Sometimes I just want a Simpson 260 so I can see how things vary. Cheapo $5 meter can come in handy then.
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Old 14-11-2014, 19:35   #26
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Re: Low voltage reading on turned off circuit.

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To "load" the circuit you could put your first two fingers (right hand ot left, not right and left) across the terminals. That would "load" the circuit.

I have a love/hate relationship with digital meters for these kind of reasons. Auto scale - hate it. Sometimes I just want a Simpson 260 so I can see how things vary. Cheapo $5 meter can come in handy then.
You are not the only one partial to a Simpson 260.

You must be older than dirt? I am.
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Old 14-11-2014, 20:00   #27
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Re: Low voltage reading on turned off circuit.

Yes, way too old.

Many decades ago I did avionics in the USCG. Forgot most of what was useful.

Vacume Tube Volt Meters, heh? Bring back memories?

I worked on airborne Loran A units. Trained on early Loran C.

I don't even pretend to try to keep up anymore.

XLTE? WTF! GSM? BFD! DSC! HUH? OMG TMI
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Old 15-11-2014, 18:12   #28
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Re: Low voltage reading on turned off circuit.

Quote:
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........... I have a love/hate relationship with digital meters for these kind of reasons. Auto scale - hate it. Sometimes I just want a Simpson 260 so I can see how things vary. Cheapo $5 meter can come in handy then.
In the field, the digital meters more often survived the "ladder test" than the analog meters.
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