Neg bus bars w/difft voltage?

[soopad00pa]

Been working on my rat's nest of 40yr old wiring and have a frustrating issue going on. There are two identical negative bus bars festooned with wires. One shows 14.3v which correlates to my battery and the other reads from 10.2v to 11.5v depending on which screw I poke with my multimeter. I'm using the same positive terminal for this testing since I'm specifically trying to get my fridge working.

There's a whole bunch of stuff on the low voltage bus, but I can't find enough stuff that doesn't work to account for all of the wiring. I do know it's not running a couple of 12v cigarette lighter sockets.

Any idea on how I deal with this? Do bus bars go bad?

[Manateeman]

Photos please.

[Jammer]

Originally Posted by soopad00pa

There's a whole bunch of stuff on the low voltage bus, but I can't find enough stuff that doesn't work to account for all of the wiring. I do know it's not running a couple of 12v cigarette lighter sockets.

Any idea on how I deal with this? Do bus bars go bad?

They get corroded. Be sure the connections are clean bright and tight, and that the connection that ties it to the other bus bar (or the battery if they both go to the battery) is clean bright and tight. A little bit of conductive grease can help matters. They sell electrical grease at home centers for use on aluminum wiring and that works well for other purposes also.


To brighten them up you can use emery cloth, a file, a wire brush, or a die grinder with either a surface prep disk or a wire brush.

[KompetentKrew]

How far apart are they?

[glenn.225]

Originally Posted by soopad00pa

Do bus bars go bad?

Not necessarily the buss bar, but wiring and connections can get corroded.
Also is there something running that may account for voltage drop?
Hard to say without seeing it.

[soopad00pa]

Thanks. So, basically do more painfully tedious work in small spaces

I hate boats!

[soopad00pa]

Everything is turned off pretty much. I turn on the breaker for the fridge to test connections and then turn it back off.

[glenn.225]

Are all those negative wires?

[soopad00pa]

Yeah, the two bars on the back wall are negative. All the positives are on the fuse panel that folds forward for access.

[Kelkara]

Just going by the black/white/green colours on some of the wires ... the black wires on left hand one looks a lot like 120V live wires, not 12V negative ... be careful.

[Jammer]

Originally Posted by soopad00pa

Thanks. So, basically do more painfully tedious work in small spaces
>>photo<<

Those aren't busbars. They're barrier strips. The one on the left has its top three terminal pairs joined electrically by a factory jumper. By the color and type of wire I would guess those are the hot side of the 120v shore power circuit. The next three pairs are also joined together and appear to be the neutral side of the 120v shore power circuit. Below that are ground wires which appear to be connected to the neutral wire though I can't quite tell from the photo. (Such a connection is not recommended and can pose various problems)

The one on the right has its top four terminal pairs joined electrically by a factory jumper and the next two pairs joined (apparently) to it by a thin piece of solid wire. There is no visible connection to the next lower pair, although it appears to have a thin piece of wire connecting it to the next lower pair beyond that.

The "dimple" type crimp tool used to install the yellow and blue wire terminations does not produce reliable crimps. You may find it necessary to replace the terminations using proper tooling, at least on an as-needed basis.

I believe you're out of your depth here and would recommend that you get qualified on-site assistance before proceeding, for your safety.


It is situations like this, where a simple-sounding question about ground busbars turns out to be based on incorrect assumptions that pose serious safety risks, that keeps me from trying to provide electrical troubleshooting assistance when I am not present in person to see what is going on.

[soopad00pa]

Ah, well. That is good to know and much appreciated.

Could it be that I'm getting the odd 10-11v reading because I'm not connected to shore power and it's just a funky reading between a live 12v pos and an off 120v?

[LoudMusic]

It also looks like there's been moisture running down that wall. That image makes me all kinds of nervous.

[glenn.225]

Originally Posted by Jammer

Those aren't busbars. They're barrier strips. The one on the left has its top three terminal pairs joined electrically by a factory jumper. By the color and type of wire I would guess those are the hot side of the 120v shore power circuit. The next three pairs are also joined together and appear to be the neutral side of the 120v shore power circuit. Below that are ground wires which appear to be connected to the neutral wire though I can't quite tell from the photo. (Such a connection is not recommended and can pose various problems)

The one on the right has its top four terminal pairs joined electrically by a factory jumper and the next two pairs joined (apparently) to it by a thin piece of solid wire. There is no visible connection to the next lower pair, although it appears to have a thin piece of wire connecting it to the next lower pair beyond that.

The "dimple" type crimp tool used to install the yellow and blue wire terminations does not produce reliable crimps. You may find it necessary to replace the terminations using proper tooling, at least on an as-needed basis.

I believe you're out of your depth here and would recommend that you get qualified on-site assistance before proceeding, for your safety.


It is situations like this, where a simple-sounding question about ground busbars turns out to be based on incorrect assumptions that pose serious safety risks, that keeps me from trying to provide electrical troubleshooting assistance when I am not present in person to see what is going on.

1+ on this, really needs some sorting out.

[Squanderbucks]

From what I see you do not have two "real" negative buss bars. You have cobbled up a couple of terminal blocks made to function as buss bars.

All of those connection points are meant to be individual with the ability to combine a few as needed to join a few things on one circuit.

But trying to use these as Buss Bars is not a great idea. Each one of the metal clips adds more current loss and points of corrosion causing further loss. Also there is no LARGE stud for attaching a large gauge ground wire. I can't see your ground wire in the photos but I bet it's too small or attached with a small ring connector to get it to fit on the wire screw.

My recommendation is to get one or two real buss bars and make sure they are connected with large gauge wires ...even when interconnected.