12VD from Neg Battery Terminal to Ground

[Bradt530]

I have gone brain-dead on this. I have 12VDC to ground. It all started after I blew N3 fuse when replacing a bad battery in my Genesis dual Battery. I blew the N3 Fuse when I accidentally touched ground. This is when I learned about the N# (fuse array). I replaced it, then I drove it for about a week. Then, while driving, everything went blank truck died . I had a new fuse array replaced it got home. Since my mechanic is on vacation. I thought I could figure it out since I understand a DVOM and how to use it.

I started checking, and I had 12VDC to ground. To eliminate things. I removed the Genesis dual battery It's been on the truck for over a year. All other accessories that I was powering off the battery are removed also. So now all I have are the factory power leads. Using a single battery with just the + (power terminals post attached), when I measure - post (nothing attached to the post), I get 12vdc from the post to ground.

I then proceeded to eliminate further. I removed all terminals going to the + post on the battery. Attaching Ine by 1 to the + post and measuring from the - post to ground. When attaching the + that goes to N2 I get 12Vdc to ground from the - post. The terminal that has two wires attached to one terminal that goes into a wiring loom (where it goes, I don't know) also has 12Vdc from - post to ground.

Since I do not have anything attached to the - Post and only touching my meter lead to it. I even pulled out the fuse block just to look at it, with no resolution.

I'm at a loss. Could I be getting feedback? I hate to just keep buying fuse arrays. ANY suggestions on the direction to go? Should I be focusing on the wiring harness that reads 12Vdc from the - post to ground? (I have crawled under the jeep to see if I could see anything.

Now I question if maybe there should be 12Vdc from - post to ground. Everything I know tells me that's not the case..

ANY IDEAS?

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[Flanders]

I have some trouble understanding exactly where the measurement is taken.

With no AUX and no connection to the negative battery terminal, and the positive side connected normally, you should see 12V from the negative terminal to the chassis ground.

I know that may seem weird.

 

[Badunit]

With the battery hooked up, 12V (nominal) from negative post to ground means you have a break between the negative post and ground. There is an intelligent battery sensor (IBS) on the negative post. The flow goes through the ground wire, through the sensor, then to the negative post. It could be that the IBS was damaged and is now an open circuit. There is also a fuse that goes to the IBS but I don't know if the sensor stops flow if the fuse is blown. And there apparently is a bus connection but I assume it is just for monitoring, not controlling.

Check the voltage across the IBS. Should be 0V but I suspect you will find 12V (nominal).

 

[Bradt530]

With the battery hooked up, 12V (nominal) from negative post to ground means you have a break between the negative post and ground. There is an intelligent battery sensor (IBS) on the negative post. The flow goes through the ground wire, through the sensor, then to the negative post. It could be that the IBS was damaged and is now an open circuit. There is also a fuse that goes to the IBS but I don't know if the sensor stops flow if the fuse is blown. And there apparently is a bus connection but I assume it is just for monitoring, not controlling.

Check the voltage across the IBS. Should be 0V but I suspect you will find 12V (nominal).

Thank you I will check that when I get off work.

 

[Bradt530]

I connected the + 12VDC Terminal using a meter It reads 0.0VDC across the IBS.

 

[Badunit]

With the battery connected you are getting 12v from the neg post to ground (body, engine) and 0v across the IBS?

 

[Gatorized]

Was the aux battery removed when the Genesis system was installed? Pictures of your set-up would be helpful.

 

[Bradt530]

With the battery connected you are getting 12v from the neg post to ground (body, engine) and 0v across the IBS?

That's right. 12V from neg battery post to ground.(engine) and 0V across the IBS.

 

[Bradt530]

Was the aux battery removed when the Genesis system was installed? Pictures of your set-up would be helpful.

Yes the aux battery was removed over 1 year ago when the Genesis was installed. I've got the genesis removed with all accessories that were hooked to it (led lights and winch ) to eliminate maybe and back feeding issues. This is really throwing me a curve.

 

[Badunit]

I guess to be thorough, take the voltage from the engine to the bolt where the ground strap attaches. From all you've said so far, it will be 12V (should be 0V). If it is 12V, it appears to be something with the ground strap or the connections on either end of it. I don't know where the other end of the ground strap is anchored so I can't tell you where to look. It would surprise me to find the ground strap damaged by a quick short, but who knows.

 

[ItsmeMrWright]

I have gone brain-dead on this. I have 12VDC to ground. It all started after I blew N3 fuse when replacing a bad battery in my Genesis dual Battery. I blew the N3 Fuse when I accidentally touched ground. This is when I learned about the N# (fuse array). I replaced it, then I drove it for about a week. Then, while driving, everything went blank truck died . I had a new fuse array replaced it got home. Since my mechanic is on vacation. I thought I could figure it out since I understand a DVOM and how to use it.

I started checking, and I had 12VDC to ground. To eliminate things. I removed the Genesis dual battery It's been on the truck for over a year. All other accessories that I was powering off the battery are removed also. So now all I have are the factory power leads. Using a single battery with just the + (power terminals post attached), when I measure - post (nothing attached to the post), I get 12vdc from the post to ground.

I then proceeded to eliminate further. I removed all terminals going to the + post on the battery. Attaching Ine by 1 to the + post and measuring from the - post to ground. When attaching the + that goes to N2 I get 12Vdc to ground from the - post. The terminal that has two wires attached to one terminal that goes into a wiring loom (where it goes, I don't know) also has 12Vdc from - post to ground.

Since I do not have anything attached to the - Post and only touching my meter lead to it. I even pulled out the fuse block just to look at it, with no resolution.

I'm at a loss. Could I be getting feedback? I hate to just keep buying fuse arrays. ANY suggestions on the direction to go? Should I be focusing on the wiring harness that reads 12Vdc from the - post to ground? (I have crawled under the jeep to see if I could see anything.

Now I question if maybe there should be 12Vdc from - post to ground. Everything I know tells me that's not the case..

ANY IDEAS?

As a career electrician, anytime we had what some called a backfeed turned out to be an open neutral or ground. I would suggest replacing the ground cable and cleaning all connections.

 

[jebiruph]

With your ground cable disconnected from the battery, measure the resistance of the cable to the body ground. It should be 0 ohms.

Also, the N4 terminal connects through a 150 A fuse just like the N3 terminal. The N4 terminal is typically unused and as a work around for a blown N3 fuse, you can move the wire from N3 to N4.

Which battery is the IBS connected to? Genesis guidance used to be to connect it to the 2nd battery and not the main battery.

 

[Bradt530]

With your ground cable disconnected from the battery, measure the resistance of the cable to the body ground. It should be 0 ohms.

Also, the N4 terminal connects through a 150 A fuse just like the N3 terminal. The N4 terminal is typically unused and as a work around for a blown N3 fuse, you can move the wire from N3 to N4.

Which battery is the IBS connected to? Genesis guidance used to be to connect it to the 2nd battery and not the main battery.

I don't remember what the ohms were. It was not 0 ohms. The IBS was connected to the second battery. To aid in troubleshooting, I have removed the Genesis system. While examining this wiring diagram, could the PCR be shorted? I would think a fuse would be blown.

 

[DylanM]

I started checking, and I had 12VDC to ground. To eliminate things. I removed the Genesis dual battery It's been on the truck for over a year. All other accessories that I was powering off the battery are removed also. So now all I have are the factory power leads. Using a single battery with just the + (power terminals post attached), when I measure - post (nothing attached to the post), I get 12vdc from the post to ground.

With the positive battery cable attached and the negative cable removed, it's perfectly normal to see 12V on your meter when you connect it from a chassis ground to the negative battery post because your meter and leads are effectively replacing/serving the same purpose as the negative cable you've disconnected.

I then proceeded to eliminate further. I removed all terminals going to the + post on the battery. Attaching Ine by 1 to the + post and measuring from the - post to ground. When attaching the + that goes to N2 I get 12Vdc to ground from the - post. The terminal that has two wires attached to one terminal that goes into a wiring loom (where it goes, I don't know) also has 12Vdc from - post to ground.

The positive cable that connects to N2 is the battery feed to the PDC which is connected to all its outputs/loads. Connecting that cable to the positive battery post and your meter between the negative post and ground makes a circuit, at which point it's expected you will see 12V on the meter.

 

[jebiruph]

I don't remember what the ohms were. It was not 0 ohms. The IBS was connected to the second battery. To aid in troubleshooting, I have removed the Genesis system. While examining this wiring diagram, could the PCR be shorted? I would think a fuse would be blown.

Move the IBS to the main battery along with the factory ground cables. Your wiring should match the diagram. If and when you re-install the Genesis system, leave the IBS on the main battery.

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