It is probably the battery

saltydogjeff

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May 12, 2013
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I am in the middle of creating a working boat. Boat specs in the signature.

Since I have begun rewiring, there has been very little time to actually test the battery. After wiring the gauges, new interior lights, and the stereo, I decided it was time to start flipping stuff on. I turned on the interior lights last night, they worked great, I was ecstatic. Today, I turn the battery switch on, and go to turn on the interior lights, no lights. I checked the battery voltage ~ 12.6, I check the terminal voltages forward in the dash, ~3.4, I check the accessory panel voltage, reading in mVs. I say ok, now I am going to continue wiring, but I am going to put the battery on charge. I finish up the dash with the 12V common line, the common ground, and the gauge back lights hooked up to a switch. That goes to accessory panel. I say ok, maybe the battery had just been out there for too long since I previously charged it, tried turning the engine over (which is stuck), maybe a couple of weeks with little power output. I look at the battery on the charger, theres a green light giving me the go ahead, then the green light disappears. Obviously cycling on the charger. I say ok, maybe this battery is like on the verge of being fully charged, lets give it a go. Install battery. Battery voltage ~12.8 V. Great. Flip switch, nothing burns. Great. Check hot line into ignition switch ~12.8V. Lights turn on. I then continue by trying to see what happened to the music. I have all this battery shouldn't I be able to get music now? No music. Flipped switch off to investigate. Flipped switch back on, checked voltage under dash at ignition switch, 4.3V. Checked voltage at accessory panel ~1V.

So, theory is, the initial charge is enough to get the line going, and then push the electrons through the accessories, except when the (+) line gets too saturated (i.e. music, gauge back lighting). And then when I secure the battery using the switch, the battery then doesn't have enough power to power the line again. The voltage differential between points seems a little extreme, 8 volts just to go forward and ~3 volts loss for 2 feet of 10 gauge. And, after the charge the ignition read the same voltage (12.8V) which would indicate very little line loss. I previously cleaned the connections to make this thing efficient.
 

Alumarine

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After charging you have to wait a while to get a true reading.
You could always get the battery load tested.
 

alldodge

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Agree with Marc need to check the battery. You could turn stuff on where your reading 4.3V, then go back to the battery and see if you still read 12V. If 12V is there start looking for a break in the line
 

saltydogjeff

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I checked the battery at the local auto store. They said it was good, so I went to work. The solution is something with the radio wiring. There is a yellow, red, and black that need to be wired. When I had the yellow on the circuit, it dropped the voltage to 4V. I do not know what this means, I have to do some research on actual stereo player wiring. Something like the yellow is a constant voltage source whether on or off (suppose to be directly battery), and the red is a hot switch lead and black is the ground for the entire stereo. Something weird going on, but I have confirmed the radio works when I hook up the yellow and red directly to the battery positive post and the ground to the negative battery post.

The good news is, I removed the rotten wood panel board behind the accessory fuse panel. My thought was that voltage was seeping through straight to ground.

Kind of sticking with the electrical stuff, I think I still got a good 10 gauge orange lead that goes forward. This was from the mercruiser 470 wiring with the voltage regulator to an ammeter. I currently am switching to the volt meter, which leaves me with an orange run in parallel with the main red 10 gauge that goes to the ignition. I was thinking there were issues with Kirchoff's laws getting the voltage drops, etc previously making me second guess wiring. But, with the stereo line off, I get similar voltage readings between the aft and forward areas.
 

alldodge

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This being a 470 I have to bow out, made way to many mistakes with them. Probably need the lead electrical expert here bruceb58 to help out with this
 

bruceb58

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Get a long test lead that will run from your battery to your fuse panel. Put one lead of the voltmeter at the battery positive and one at the positive of your fuse panel. Turn on some loads and measure the voltage. In theory, should be close to zero volts but will always be something.

Do the exact same thing but do between the negative of the panel and the battery. You will find one has a huge voltage drop and will point you to what side to fix.

You sure you have an ammeter? They stopped using those way before 1976.
 
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saltydogjeff

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So here is an update. I tried to understand a little and am looking for some electrical help. I drew a diagram to provide some information.

Wiring.jpg
I read the voltage at the fuse panel while turning the lights on and off. The voltage went from 12V to about 6V from going off to on. I am confused why I do not get 12V consistently at the fuse panel.

Do you still want me to do the long lead thing? Are you leading that this might be a ground thing?

I did have an ammeter. I recently took out all the gauges and there is a volt meter in its place. It had a large orange running to one side and a large red running to the other. I am still waiting on the trim gauge in the mail.

gauges1.JPG
 

saltydogjeff

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There has to be some sort of wiring going in series. I have a feeling it might be back towards the engine rather than forward, but some how the power wires and the ground are getting crossed over causing the voltage drop. That is the only way the voltage would drop from turning a device on and off.
 

bruceb58

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That is the only way the voltage would drop from turning a device on and off.
NO...you have a resistive connection between the panel and the battery. Did you do the tests I suggested?
 

MH Hawker

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thats what i was thinking bruce, one of the thin film covered terminals

clean the battery terminals no mater how good it looks
 

saltydogjeff

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I cleaned the battery terminals like mad today. I also made myself a long test lead connection to the battery and started testing. I found out there is a solution, which appears to be a fault connection. Basically I got it all to work in the end. Which is why I need some run time to check things over.

Anyways, I was playing with leads, putting the lights on, then off, then on. I found that two gauges - fuel and oil, will peg high when the lights are on and things are not working correctly. And will return to zero when the lights are turned off. I reviewed the connections behind the panel and I thought everything was separated. I do not even have power going to the gauges right now, they are disconnected at the upstream fuse. When it wasn't working correctly I would get a 6.6 volts at the fuse panel and 5.7 volts ground to battery ground. That was really the only reading I got. I understand the method that can be used with this long lead because you can isolate the positive and the ground side, depending on which side you want to work off of the battery. A reading less than the battery voltage (~12V) would indicate a resistive load/connection to ground when hooked up to the positive battery and testing ground cables?

Edit: So it was working incorrectly - getting the 6.6 volts, and then one time it just seemed to work correctly, reading 12 volts, had the lights, gauge lights, and stereo running.
 
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Fed

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You didn't connect your Voltmeter in series like your Ammeter was connected did you?
 

bruceb58

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You didn't do the tests correctly. You are trying to measure voltage drops. Supposed to be ZERO volts.

I think Fed may have guessed your problem though.
 

saltydogjeff

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I did not connect the voltmeter in series. It is in parallel with the rest of the gauges, running off of a purple wiring according to the wiring diagram for battery meter. No need to run all that current through a gauge just to get a voltage reading.
 

fishrdan

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What did you do with the two thick (10ga?) wires that were connected to the old ammeter? They should be connected together to complete the circuit. IE: remove ammeter, then bolt the 2 thick wires together, you can do this on the + terminal of the voltmeter. Clean the lugs well before connecting the wires together.

I agree with Bruce's long lead testing, from the battery to dash. Figure out where the voltage drop is coming from. Might not hurt checking the engine's wire harness cannon plug for corrosion.

Is this a running boat that just got the problem after swapping gauges, or a project boat of unknown condition?
 

saltydogjeff

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I think I have found the problem at a connector underneath the dash. I agree with using Bruce's long lead testing. It provides testing of individual circuits while under load. There is another 8 (or 10) piece connector under the dash that definitely cut the music when I pushed it. I read the voltage at the fuse panel afterwards where it came in at 6 volts or so.

I have completely disconnected the orange wire from the circuit. It connected in the engine bay of the boat where the alternator connected to the red positive battery wire, providing a parallel positive circuit. It is disconnected from the front and the back of the boat being just a wire. I have not thought of a good use for it.
 

fishrdan

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Cannon plug is the main electrical harness connector at the engine, about 2" around.
 
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