No DC power, Where to Start?

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Max Simmons

Max Simmons

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Joined
Oct 15, 2007
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Ocean Alexander 38'
I will admit that electrical systems are probably my weakest strength, and this has me stumped.
Yesterday we went out for a day of crabbing. Everything was up and running as we left the dock. Dropped the anchor after a short 30 minute cruise. When I hit the windlass deck button to raise the anchor after about an hour, nothing. Went inside to make sure the breaker was on, and it was, but the DC panel was dead. Nothing was working. Volt meter on panel was at 0. After a shor period, maybe 3-4 minutes, the voltmeter went up to 14, bounced around a little bit, then stopped at little over 12. Went back out to raise anchor, same thing. Went back in and panel was dead. After a bit came back on. Turned on bilge pump at breaker panel and voltmeter went to 0. When I turned it off, voltmeter went back up. Tried a few other things that are swithced directly at the panel, spreader lights, anchor lights, etc. same result. Voltmeter at panel went to 0, then would go back up.
Battery meters show as fully charged. Replaced 2 house 8D's 2 years ago, voltmeters at helm show both charging at 14 volts.

Any idea where I should start? Thanks
 
Max Simmons said:
Any idea where I should start? Thanks
Click to expand...

Clean your battery terminal connections for a start and make sure they are tight.

If that doesn't cure the problem then:

Make up a test light using a 12V high wattage bulb and start tracing power until the bulb dims because of the high resistance connection.

Don't depend on a digital multimeter to tell you much about this problem, it has too high an impedance to detect the most likely fault.
 
Greetings,
Yup, what Mr. Rick said. One other quick, dirty and easy test is to beg or borrow one of these things...

CBC-BT-100_SN.jpg


to test your batteries under load. If you choose to buy one, they're less than $50. How did you get your boat started?
 
A dirty/poor battery connection can ruin your whole day!! Check your batteries first. Clean and tighten.
 
Max Simmons said:
I will admit that electrical systems are probably my weakest strength, and this has me stumped.
Yesterday we went out for a day of crabbing. Everything was up and running as we left the dock. Dropped the anchor after a short 30 minute cruise. When I hit the windlass deck button to raise the anchor after about an hour, nothing. Went inside to make sure the breaker was on, and it was, but the DC panel was dead. Nothing was working. Volt meter on panel was at 0. After a shor period, maybe 3-4 minutes, the voltmeter went up to 14, bounced around a little bit, then stopped at little over 12. Went back out to raise anchor, same thing. Went back in and panel was dead. After a bit came back on. Turned on bilge pump at breaker panel and voltmeter went to 0. When I turned it off, voltmeter went back up. Tried a few other things that are swithced directly at the panel, spreader lights, anchor lights, etc. same result. Voltmeter at panel went to 0, then would go back up.
Battery meters show as fully charged. Replaced 2 house 8D's 2 years ago, voltmeters at helm show both charging at 14 volts.

Any idea where I should start? Thanks
Click to expand...

Check your batteries, check the connections, then check your wiring.
 
And don't forget to look at the fuses and fuse holders for corrosion and connections. Obviously a blown fuse stays dead, but bad connections can come and go.

If you're huntng for dropping voltage, a DVM is more accurate than a light bulb if you know how to read it.
 
Could he have a thermal circuit breaker that is opening then reseting itself when it cools?
 
Don't do it!

Max,
I locate problems similar to this a lot for our customers. Like Rick suggested, a test light is the right tool. But my approach is to NOT clean any terminals OR shake any wiring. This may solve your problem, but probably short term. I suggest that you have someone ready at the breaker panel, put your test light alligator clip at the negative battery post clamp and probe the other end at the center of the positive post. Have the bilge pump breaker turned on and confirm the light does not dim or go out as the breaker is tripped. Continue the process "downstream" as far as is possible onthe positive side, and if you have not located the bad connection reverse the process. Alligator clip on the positive post battery clamp and the probe onthe center of the NEGATIVE post th start, then continue downstream. Let us know what you find!
 
Everybody is right on here. It's probably not your batteries and is more likely an issue with your wiring connectors between the battery terminals and the main panel. Start at the batteries cleaning the terminals, cable ends all the way through the battery switches up to you DC panel,testing as you go and pay extra attention to your grounds.

It may take some time, but 12 volt systems are fickled and a dirty connection, bad battery switch or old circuit breaker or ground may look good and tight, but it may not carry a load and will give you the results that you are seeing.

Like Rick B. said, a volt-ohm meter or multimeter will tell you if there is 12 volts or if ground is present, but it won't tell you if a circuit will carry a load. So you have to put each test point under load to determine where the problem is. It may be a two man job to trace it out, so don't be afraid to ask someone to help you.

I use an old combo (two filaments) brake light/turn signal light socket and bulb with 10 inch long pigtails as a tester. It was salvaged from an old car and it is simple and works great.

Good luck
Larry B
 
As menruoned before, start at the batteries as the windless is probable wired directly from the batteries and not through the main panel. If both the windless and main panel are dead it's at/before they junction off. I would check/clean/tight the battery terminals, the battery on/off main selector switch, and the bus bar where they junction off. There might also be fuse/breaker in the same area.

Wing nuts are not recommended as they come loose easily should be regular nuts with lock washers. Also stacking should be limited to 2 maybe 3.

So how did you get the anchor up? Your SO must be very strong! :D
 
RickB said:
............Don't depend on a digital multimeter to tell you much about this problem, it has too high an impedance to detect the most likely fault.
Click to expand...

If you understand electricity and know how to use it, a digital multimeter is the best tool to diagnose electrical problems. You can't accurately jusge voltage or resistance by the brightness of a test lamp.
 
rwidman said:
If you understand electricity and know how to use it, a digital multimeter is the best tool to diagnose electrical problems. You can't accurately jusge voltage or resistance by the brightness of a test lamp.
Click to expand...

A digital multimeter is a fine diagnostic tool. But when you have "nuthin", accuracy to less than a tenth of a volt is unnecessary.
 
Forkliftt said:
A digital multimeter is a fine diagnostic tool. But when you have "nuthin", accuracy to less than a tenth of a volt is unnecessary.
Click to expand...

It's hard to do good work if you don't have good tools. :rolleyes:

Granted, one tenth of a volt accuracy is not usually needed, but judging voltage drop with a lightbulb is about as redneck as it gets.

My brother in law claims he can test nine volt batteries with his tongue. He is a redneck and proud of it.

Me, I use a meter when diagnosing electrical or electronic problems. They used to pay me quite well for my expertise and skill. :)
 
I just bought a digital multi meter because everyone said I should have one. I don't even know how to use it, but a test light. I can see a light go off or on.
I at least know if I have power or not. So that is what I use

SD
 
I use a meter routinely as well, but recently ran into a situation where the light bulb also came in handy. I was installing a new fishfinder/depth sounder on my dinghy using the terminals on the back of the "accessories" cigarette lighter outlet(needs a new name now so few smoke!!). The fishfinder worked fine but when I plugged in my handheld spotlight to the accessory outlet it would not light up. Checked the voltage -- fine at 12V+. Tore apart everything looking for the problem. Finally checked with a light bulb at the same terminals feeding the fishfinder --- no light!! Long story short, the wiring had corroded to the extent that it would only carry enough current for the FF, not enough to light the spotlight or the the test bulb. The bulb came in quite handy. Maybe next time I'll try licking the terminals!!
 
Maybe next time I'll try licking the terminals!![/QUOTE]

Now That really cracks my ass up
 

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Chrisjs said:
I use a meter routinely as well, but recently ran into a situation where the light bulb also came in handy. I was installing a new fishfinder/depth sounder on my dinghy using the terminals on the back of the "accessories" cigarette lighter outlet(needs a new name now so few smoke!!). The fishfinder worked fine but when I plugged in my handheld spotlight to the accessory outlet it would not light up. Checked the voltage -- fine at 12V+. Tore apart everything looking for the problem. Finally checked with a light bulb at the same terminals feeding the fishfinder --- no light!! Long story short, the wiring had corroded to the extent that it would only carry enough current for the FF, not enough to light the spotlight or the the test bulb. The bulb came in quite handy. Maybe next time I'll try licking the terminals!!
Click to expand...

Being more experienced in the field, I would have clipped the meter's leads to the connections on the accessory socket, measured 12 volts, plugged in the spotlight, noted the voltage drop, and determined that there was a high resistance connection somewhere in the circuit, just as you eventually did.
 
Thanks for the tip, rwidman.
And I did say lick the TERMINALS, Skipperdude!!!!
 
skipperdude said:
I just bought a digital multi meter because everyone said I should have one. I don't even know how to use it, but a test light. I can see a light go off or on.
I at least know if I have power or not. So that is what I use

SD
Click to expand...
If you don't know how to use a meter, by all means keep it in the original packaging. ;)

You need to know two things:

1) Obviously, you need to know how the meter operates. How to turn it on, and how to set the switches and where to plug the leads in.

2) You need to know where to connect the leads in the circuit you are troubleshooting and how to read and interpret the results.

If a light bulb does what you want it to do, by all means, break out the light bulb when you have a problem. I don't own a test light. I own three or four meters. One is on the boat, the rest are at home. The meter can do everything a test light can do (except light up the area I am working in) and more.
 
Dude, could you come up to Alaska and help me fix my 12 volt system I have a ghost or is it a gremlin in my system somewhere.

I can't even talk about it becaus I don't know where to start.

I know at one point my entire hydraulic system became electrified to the tune of softening the petro wrap on the fittings and they are connected by hydraulic hose . No wire.

Another story.

Sd
 
rwidman said:
It's hard to do good work if you don't have good tools. :rolleyes:

Granted, one tenth of a volt accuracy is not usually needed, but judging voltage drop with a lightbulb is about as redneck as it gets.

My brother in law claims he can test nine volt batteries with his tongue. He is a redneck and proud of it.

Me, I use a meter when diagnosing electrical or electronic problems. They used to pay me quite well for my expertise and skill. :)
Click to expand...

Ditto here. $1.50 a minute and in my industry productivity and proficiency is very important. Let's don't split hairs here. All I'm saying is that in a situation like the OP had, a test light- in my opinion- is much more productive. I use to joke around that I could read voltage with my test light too. Most folks wouldn't / couldn't prove you wrong any way :). As you and I know, reading all these voltages are great, but it really gets down to whether or not the circuit can hold up under a load. The OP saw his panel go to 0 volts under a load (bilge pump turned on) so that's why I suggested to use this as the "load" as he tested the circuit. IMHO the multimeter comes in later when you have voltage to check :)!
 
Thanks for all the input. I do have actually have 2 multi-meters on board, but do like the low tech lightbulb technique. I will get down there later this week and start checking it out.
Pulling the anchor by hand does make me appreciate the windlass even more! Glad we were only in 24' of water
 
Forkliftt said:
Ditto here. $1.50 a minute and in my industry productivity and proficiency is very important. Let's don't split hairs here. All I'm saying is that in a situation like the OP had, a test light- in my opinion- is much more productive. I use to joke around that I could read voltage with my test light too. Most folks wouldn't / couldn't prove you wrong any way :). As you and I know, reading all these voltages are great, but it really gets down to whether or not the circuit can hold up under a load. The OP saw his panel go to 0 volts under a load (bilge pump turned on) so that's why I suggested to use this as the "load" as he tested the circuit. IMHO the multimeter comes in later when you have voltage to check :)!
Click to expand...

If you want to find out if you have the proper voltage to a load, the best and most accurate way is by using that load. For example, you could be testing the power circuit to a bow thruster that draws 60 amps. That little test light could light up just fine as a load but the thruster still wouldn't work. Measure the voltage at the thruster as you try to operate it and you'll know if there's a drop and how big of a drop there is.
 
RW, I think the point here is that Max had no voltage most of the time. Even when he tried to run a bilge pump. This- to me- says that his problem was probably a poor connection. AND back to my original point. Don't start screwing with wires and terminals and components until the poor connection has been isolated. Clean and test is not a dependable troubleshooting process for a wiring issue IMO. The process is the same for 1 amp bilge pump and a 50 amp windlass. We dont carry a battery load tester on our service vans. We have a starter or electric hydraulic pump motor for the "load" which is part of the machine we are repairing. Again, there are several ways to locate a problem. I fool with this stuff all of the time and if we get it wrong, we lose money the second time. This inspires us to approach it in the most effective manner:)!
 
After you find the problem , perhaps an upgrade that takes time and almost no bucks might be in the cards?

Simply take one sample from a circuit breaker to discover the size of the screw used.

Usually #8 but ,,,.

Then get a box of 100 copper flat washers and a box of 100 bronze star washers, either or both can be tinned ..

Install the copper on the terminal end and then the star washer.

As most circuits will at times get warm the star washer will maintain tension after the terminal cools.

The copper is to upgrade the ampacity of the terminal, copper is better than bronze, MUCH better than SS or common steel.

Cheap, not fast to do , but with a scotch brite pad , at least a rain day wont go down the boob box black hole .

FF
 
OK, Finally had some time to do some checking on this. All of the connections at the windlass looked good. No corosion and all snug. I did find significant corrosion on the main battery terminals. I have 3 8-D's. 2 for the house and one for starting. The corrision was limited to the 2 house batteries. The starting battery had none. Interestingly, the 2 house batteries are the two I recently replaced. The starter battery is at least 7 years old and still going strong.
I removed and cleaned the cable ends. I have not yet been able to try the windlass under load, but I sure think this is the problem. Now, shy would these corrode so much?
 
Always start with the simplest thing to check!!! No meters, no fancy tools, just common sense!! Your thruster draws between 300 and 500 amps (really that much!!) depending on model/size. I would guess the terminals were not tight enough, dirty or you have a low-conducting stainless washer in there. The thruster draws enough current to find the weakness in the connection and to arc/burn if not well connected. Your other current draws are probably much lower and could probably get by until you hit the thruster button!!
 
Max Simmons said:
OK, Finally had some time to do some checking on this. All of the connections at the windlass looked good. No corosion and all snug. I did find significant corrosion on the main battery terminals. I have 3 8-D's. 2 for the house and one for starting. The corrision was limited to the 2 house batteries. The starting battery had none. Interestingly, the 2 house batteries are the two I recently replaced. The starter battery is at least 7 years old and still going strong.
I removed and cleaned the cable ends. I have not yet been able to try the windlass under load, but I sure think this is the problem. Now, shy would these corrode so much?
Click to expand...
Good question. Wing nuts or clamps? Is the battery box well ventilated? Or other terminals ok besides the main ones? I am convinced that most corrosion problems on post type batteries are created by us. New battery installation And the clamp bolt and clamp are in poor condition. During the install the clamp takes excessive force to try to close. We don't support the post and crank down on the old bolt followed up by a few shots with a hammer:) connection made, but the seal between the lead post and plastic case is now cracked and when charging the gasses like to slip there and begin corroding our new battery post. And the first time you pull the clamp It takes even more force to turn the clamp nut and so the cycle continues. Snap makes a great set of battery pliers that helps with battery work.
 
One of My Best and most often used tools in my tool bag is called a Power probe.
If you do a google search you will see what it is, but It was the best $100 I have ever spent, besides my divorce. (who woulda thunk she would EVER tell me I couldn't have a boat).

The Power probe is usually the first thing I reach for when I have a DC system that isn't working properly, and is the cats meow for troubleshooting a system.

Michael
 
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