Very Baffling electrical problem

[Nicholson58]

My experience is to re-visit anything you or you mechanic did sinc it last worked OK.

Usually a loose wire somewhere. It could even be a sense wire on your charging system. I have a set of 50 foot two conductor with aligator clips on each end. I use this & a VOM to jump power and check continuity of individual circuits and wires.

If, as you note, the voltage jumps around you may get lucky and find the loose wire.

[Lake-Effect]

You've been given alot of good troubleshooting advice. With all of this, some daylight and a clear head, you should be able to trace the 12v power from the batteries to the battery switch and to the panel.

As mentioned, it might be the battery to ground connection. Another culprit can be the nuts on the back of the battery switch.

Anywhere there's a physical connection, try to move it by hand, or give that screw or nut a bit of torque with the right tool to confirm it's not loose.

A 12v lamp or spotlight with clips to the panel will give you visual confirmation of voltage at the panel, as you inspect and touch each connection.

Be methodical, doodle up the path on a piece of paper and check off every connection you check.

[sailorchic34]

So what was the volt measurements at the batteries with the battery switch off and battery charger off. A good battery that's charged would have 12.7 volts or more. A 12.0 volt reading means the battery is very low at maybe 10% charge. Check each battery.

Assuming the battery voltage is 12.7V, now measure the voltage at the panel with the battery switch in #1, then #2 and then both.

Now start the engine and read the voltage at the panel. It should be somewhere above 13V, Ideally 13.8 to 14.4V's.

Then stop the engine and turn the battery charger on and read the voltages again at the panel with the switch in #1, #2 and then both.

My wag ("wild a** guess" an engineering term BTW) is one or both batteries are dead, or the alternator is dead, or both.

[Finistere]

Turn your battery charger off when you do all this testing.

[RLewis]

Sailorchic34- thanks- this sounds like a great approach. I confess I do not have an exact reading of the voltage as I was doing a very cursory look at things and needed to get my crew back home after squandering the day,I had simply taken a reading with my multi tester across the terminals of each battery and really did not see the actual voltage- just more of a quick look that yes voltage was registering, but will follow this approach and find out.
But- if one or both batteries were dead- wouldnt the engine either not start or at least turn over with difficulty from a low bat #1 and possible dead bat #2?

Once back at the slip I had thought that maybe the alternator had given up and while under way maybe just the VHF could have drained 2 questionable batteries. But when back and tied up I shut the engine down and restarted several times and it turned over as it always has very strong cranking power.- shore power was not hooked up at this point. Granted with this all being new to me I am no doubt missing something (lots?) but it just seems that the batteries are as strong at the end of this day as they were when I started in the morning.
That said what you say seems to make very clear sense.

I guess tomorrow should be very telling after I can apply all this great advice

Thanks much Randy

[Boracay]

My guess: The alternator is not being excited and your batteries are not charging.

You should be able to find a small wire on your alternator that looks like it's not doing anything. Check that it's secure on the alternator then trace it back to the batteries.

It may go through a few other devices on the way. Check that it is secure on each and finally check that it is secure on the batteries.

Look for corrosion and loose wires. I would not recommend unscrewing anything until you have a way of fishing small bits out of your bilge.

[JK n Smitty]

I'll chime in with a little advice/comments.

1) what was you battery selector switch set to? Battery #1, #2, both? (By the way, never turn this switch while the engine is running, you could blow your alternator)

2) you said you checked your terminals visually and with a mm. What about physically? If the were covered with a heat shrink but not crimped correctly (or soldered) they could physically separate but not look like it.

Here is what I suspect, you have a bad connection in your positive wires on battery #1, most likely at the new positive bus you mechanic installed. The reason your 12 volt outlets work is that the PO connected them directly to battery #2 via the 1/2/both switch.

There is a guy who posts on here under the name Maine Sail, he also has his own website at compass marine pbase and a forum on sailboatowners.com. The guy is a boat electrical system god and extremely knowledgable at all things boating. I highly recommend you look up his stuff

[captain58sailin]

After you check your connections at the batteries, battery switch, check your power at the panel, I assume that you have a main terminal at the panel. The other thing would be to check for a fuseable link where your primary power is connected. Agree with previous posters regarding your ground, grab a hold of it and make sure it is well secure. I first thought that with the jostling that perhaps your marine terminals might be loose on your battery posts, or that the wires going to your marine terminals have become loose. As with your other posters, start at the source and methodically work your way to the panel, then check the panel.

[zeehag]

how many years ago did previous owner buy the batteries--sounds like when mine went dead and i had to replace all my batteries to have a good electrical system...good luck.

[GrowleyMonster]

If you get a good start from battery 1 then obviously it is holding a reasonable charge. Try starting on batt 2. Isolate the batts and make sure they are okay.

[bglad]

Originally Posted by Kettlewell

My initial guess would be a bad ground somewhere, most likely from your battery to your electrical panel. For some reason those outlets that are working may be getting a ground from somewhere else. Clean and check for tightness where all cables connect at the batteries and on the engine.

I agree with Kettlewell. The DC outlets are getting a ground from somewhere else and the engine harness is supplied power independently from your DC panel thus you are able to crank and charge your batteries.

Ideally your panel should be grounded to a buss near the batteries or directly to the batteries. Sometimes the engine gets used as a buss and the connections will be made at different points on the block and that may be your problem. You need to run down the ground path from the panel all the way to its source and check each connection. Check visually but also tug on them to make sure they are secure and look for bulges in the insulation that indicate the wire is corroded and possibly separated inside.

If you have a long enough test lead you could connect your meter to your panel positive and your test lead to the battery negative. If you get the same voltage as you show directly at the battery then you have a ground problem. Test it the other way too attaching to the negative at the panel and battery positive.

If you want to test the ground theory run a new one to the panel easiest way and see if it powers up. Just don't try to run too much if you use a small wire size.

[Badsanta]

All good advice. But the best thing I bought was several boat electric books. Really helped me.

[skipmac]

So if I understand correctly, you are still able to crank the engine but have no power to lights, pumps, etc?

If that is the case then the batteries are not totally dead so the problem has to be either in the battery feed or ground to the DC system. My guess is the ground.

CAUTION. Just measuring voltage will not always find a bad circuit or bad connection. If you have a loose or corroded connection you could have some voltage present all over the system but the connection might not allow any current to pass. So voltage looks good until you apply a load, then drops to zilch. So, to get a valid test of voltage at points in the system you have to make sure there is a load on the DC system that will draw some power and reveal a bad but not completely open connection.

[sailorchic34]

Assuming there is not a separate start battery, then I'm going to fall back to the kettlewell camp. It just about has to be in the ground.

[RLewis]

Success !! Thanks to all of you for the insight and advice. I began at the beginning and began tracing all the wires and as many of you said- it was in fact a ground wire problem. The main ground wire that feeds the panel originates at the engine block. Although it had a nice tight connection to the bolt/stud into the engine block, the wire inside the crimped fitting had broken and with just a bit of a tug the wire and few unbroken strand came right out of the teminal fitting.
Replaced with a new fitting and all is now back in working order. I learned much more about my boats system and I do appreciate all of the input I recieved on the forum.

Thanks again Randy