Trying to figure out 12v short

[SunnyD]

My 12v outlet is shorting on my 2020 Yamaha SE. I've continuity tested without the fuse and both 12v sockets (dash and port transom locker) and the fuse terminal itself with a negative result. With fuse in, (house battery off obviously) both 12v sockets test positive.
The negative fuse terminal test leaves me most confused since this contradicts the positive tests. It's awkward to get the test nodes in the fuse terminals so while I'm pretty sure I had good contact, I'm not 110% sure.

Any ideas?

 

[tdonoughue]

So, first: how do you know the 12v outlet is shorting? What were the symptoms? Blown fuse? Or did it stop working?

Then, let me understand your test better, please. You did a continuity test between the 12v socket and one side of the fuse block? And it showed no continuity (that is, no electrical path)? And I assume a) you were going from the positive of the 12v to the fuse block and b) you tried the other side of the fuse block as well (one side of the fuse holder should have no continuity; the other should).

Then you put the fuse in and tested again between the positive of the 12v and the fuse block and got a positive result (that is, current flowing). That should be the case to either side of the fuse block with a good fuse in there (with a blown fuse, it will be just like no fuse, of course). If I'm understanding correctly what you did...

Depending on the type of short you are trying to trace, the continuity test may or may not tell you anything.

Once we get these questions sorted, should be able to help you get to the promised land.

 

[SunnyD]

Thanks for replying. It may not be a short. My understanding of circuits is not great. The fuse blows when there any draw on it from something plugged in. This should point to the problem being with the thing plugged in, but the thing being plugged in has a 12a fuse that is not blown. I've also plugged the device into my car outlet with no issues.

Here's a diagram of what I'm guessing is the circuit layout given what I've tested so far and my limited understanding of how this stuff works. My assumption is that when the house battery switch is off, the entire circuit should remain open (no connection).

My continuity tests where: (House battery switch off for all tests)

1) Positive and negative terminals for Helm 12v Outlet with good fuse in. Result: positive connection
2) Positive and negative terminals for Stern 12v Outlet with good fuse in. Result: positive connection
3) Probe on both sides of empty fuse outlet. Result: negative connection



One possibly related detail. My house battery seems like it's draining quickly compared to what I've read is normal. I have the stock Wetsounds amp on at about half volume only and it will go from ~12.8 volts to ~12.3 volts in probably under 60 minutes. This is with the stock solar tender (e-series).

My wild guess that might explain both symptoms is there's something drawing power on the 12v accessory circuit and when anything else is plugged in causes it to overload and blow the fuse. Everything else seems to work though even with the fuse blown except for the 12v outlets.

 

[fatboyroy]

Replace the outlet maybe?

 

[FSH 210 Sport]

Okay, let’s start with the thing (device) that is being plugged in. You say the device has it’s own 12A fuse? Perhaps you could try a smaller fuse in the device to see where that fuse blows? Like say a 6 A ….

Your drawing shows a 20A fuse that is feeding the two 12 V outlets, is that the OEM fuse?

Have you tried plugging the device into both the stern and helm outlets with the same results? Have you tried other devices in those outlets to see if the OEM fuse blows?

The voltage decay you are seeing on your battery sounds pretty normal for a lead acid battery. Do a simple test, check the battery voltage with a multimeter, not the connext gauge, while the battery has been at rest for 24 hours with the battery switch off. Then turn on the house battery switch with all devices off and measure the battery voltage. If it starts dropping then there is a load somewhere. If there is a short I’d think the 20A fuse would blow just sitting there unless there is a problem with the 12V outlet itself.

Several variables here, do you have a on board charger or similar smart battery charger that can put out 10 amps? If you are comparing what the battery voltage is just after you shut off the engine(s) to a 60 minute usage test, that’s not a good test. Also, do you have a factory installed two battery set up with a BEP battery switch and DVSR?

 

[SunnyD]

Your drawing shows a 20A fuse that is feeding the two 12 V outlets, is that the OEM fuse?

Yes

Have you tried plugging the device into both the stern and helm outlets with the same results? Have you tried other devices in those outlets to see if the OEM fuse blows?

Yes plugged into both. No haven't tried other devices

If there is a short I’d think the 20A fuse would blow just sitting there unless there is a problem with the 12V outlet itself.

This is my main confusion.

Regarding nothing being connected. There's kind of no way to do this with the lcd display always on. Which also means while it's on it's also pinging for depth.

Several variables here, do you have a on board charger or similar smart battery charger that can put out 10 amps? Also, do you have a factory installed two battery set up with a BEP battery switch and DVSR?

No smart charger yet. It's dry stacked and I have no place to plug in. I'm planning on getting a charger and bringing tgw house battery home to charge soon.
Yes, factory BEP battery switch and Dvsr.

 

[SunnyD]

Replace the outlet maybe?

Pretty sure it's not the outlet. I have one of the outlets off and am testing the leads directly.

 

[tdonoughue]

So, your first two tests indicate there is a problem. If you are testing continuity between the two poles of either of the outlets with the battery switch off, there should not be a completed circuit and your continuity should be negative.

The test on either side of the fuse outlet is as it should be; we expect no completed circuit in that situation.

Problem is that the tests you describe would point to a short between the positive and the negative wires, somewhere between the fuse and the outlets (for the positive) and somewhere between the outlets and the battery (for the negative) (presuming there is nothing else on the circuit other than the 2 outlets). But if there were such a short, you should be blowing the fuse immediately when you turn on the battery--no need to plug anything into the outlet.

Unless the act of plugging something in is what is causing the short. This will sound dumb, but check that a child did not put a penny into one/both of the outlets. Also check the connections on the outlets and the back of them to make sure there are no faults there.

 

[SunnyD]

So, your first two tests indicate there is a problem. If you are testing continuity between the two poles of either of the outlets with the battery switch off, there should not be a completed circuit and your continuity should be negative.

The test on either side of the fuse outlet is as it should be; we expect no completed circuit in that situation.

Problem is that the tests you describe would point to a short between the positive and the negative wires, somewhere between the fuse and the outlets (for the positive) and somewhere between the outlets and the battery (for the negative) (presuming there is nothing else on the circuit other than the 2 outlets). But if there were such a short, you should be blowing the fuse immediately when you turn on the battery--no need to plug anything into the outlet.

Unless the act of plugging something in is what is causing the short. This will sound dumb, but check that a child did not put a penny into one/both of the outlets. Also check the connections on the outlets and the back of them to make sure there are no faults there.

Good idea. One socket was completely off. I was testing the leads themselves. The other one I verified nothing was in it.

What I'm left with my continuity test must somehow be invalid. Somehow the switch being off must complete the circuit. I agree that the fuse should blow immediately with the switch on if there's a short.

I probably need to plug a few more things in with varying power draw.

 

[tdonoughue]

Normally one would not use a continuity test to diagnose a blowing fuse (although, as you demonstrated, it can provide some useful info).

Normally with a fuse blowing, if you can't determine what is making it blow, you start by removing all of the devices from the circuit. If the fuse still blows, you have a problem with the wiring and you look there. Otherwise, you add things back one by one until the fuse blows and then you have determined which device (or connector or whatever) is causing the issue.

For a compound issue (which you may have here), you need to use an ammeter to measure the amperage draw. Again, you remove all of the devices from the circuit. Measure the amperage at the fuse. It should be zero. If it's not zero, you start following and testing wires to see which one is leaking current until you find your short. Then you add back a device and repeat until you have traced all of the leaks that are causing your issues. BTW, you may be able to tell, you can do this method from the get-go and skip the first method if you have an ammeter. The inductive ammeters are best/easiest as you don't need to break the circuit to use them.

It may be in your case that there is some partial short (like through an electronic gadget or something) that is drawing too much current (like 17 amps), so that when you add anything to that at the sockets you blow the 20 amp fuse. That said, 20 amps is a lot of juice. So is 17 amps. If that is your issue, would be surprising to not see other issues as well (smoking parts, things not working, etc.).

 

[Ericd]

<<<. I've also plugged the device into my car outlet with no issues. >>>

Have you checked the fuse size in your car?
Maybe it’s 30a

I am suspect of “the device” as being the problem.
Have you tried anything else in the plugs?
(Sorry if I missed something in the previous posts)

 

[SunnyD]

[/QUOTE]

Have you checked the fuse size in your car?
Maybe it’s 30a

I am suspect of “the device” as being the problem.
Have you tried anything else in the plugs?
(Sorry if I missed something in the previous posts)

The fuse in my car is 20a also. Also. The device itself has a 12a fuse on the plug. I will be trying a few more devices on it next outing.