Positive Ground Battery Connection

[72Thunder]

Hi all,
I have just started the tear down process of my '72 C10 and when it came time to take off my passenger side fender I noticed my positive battery wire had been grounded to which looks like a factory piece on the fender. We thought it was alright cause the truck could start and drive just fine but as soon as we figured we didn't need it we took it off it but it never powered up. So we found a new "ground" for it (rad support), it started to spark and eventually caught on fire. i am confused by this as after everything cleared up we put it back on the fender and everything started up all fine and dandy. Is there something I'm missing?

[72Thunder]

Here's another picture

[Jim53066]

Is there something I'm missing?

Yes, that is not a ground, that is a junction block for the hot wire. The stud rests in the plastic mount and never touches the fender.

Jim

[REEDS 72]

NOT A GROUND/take pics and put back together as you found it.

[LockDoc]

-
Also, the black wire beside it with the integrated fuse holder (4amp) needs to be hooked back up to the junction block or your amp meter won't work. There should be another fuse holder just like it on the drivers side of the core support. Make sure the fuses are good and the contacts are clean....

LockDoc

['68OrangeSunshine]

Sounds like you fried your old Fusable Link. That needs to be replaced with another similar length of same-gage fusable link wire.
My Dad had a '59 Jaguar that really did have a Positive 'Earth' System. Lucas Electrics. Now I know why the Brits drink warm beer... [Their fridge is broken].

[kcsa75]

Originally Posted by '68OrangeSunshine

My Dad had a '59 Jaguar that really did have a Positive 'Earth' System. Lucas Electrics. Now I know why the Brits drink warm beer... [Their fridge is broken].

[72Thunder]

Hahaha that's funny. Thanks all for the replies and information. Checked it out even further and got everything working as it should the correct way without any fires this time! Definitely appreciate the input.

Thanks,
Darcy

[54blackhornet]

Why did GM run the positive wire through that black plastic block on the fender ? What is that connection for ?

[HO455]

I believe it's primary reason is for the fuseable link. Which is between the battery clamp and the insulated post. If the fuseable link blows it can be replaced without cutting into the harness. I'm pretty sure 67 was the first year for fuseable links and by 73 GM had decided there was no need for an easily replaced fuseable link so it was integrated into the harness to save money and confound generations of shade tree mechanics.
Its secondary use is for one leg of the amp guage wiring. It is connected at the insulated post. Having that connected to the insulated post keeps the fuse and fuse holder away from the battery post and its corrosive fumes.

[slikside]

Originally Posted by 54blackhornet

Why did GM run the positive wire through that black plastic block on the fender ? What is that connection for ?

One reason is that is where the alternator joins with the battery. Think of it as that wire gets the juice to charge the battery from that post, which is supplied by the alternator. My alternator wiring runs to the radiator support, along the top inside edge and exits right above the battery. There is a 10 or 12ga red wire that terminates on that block. Then a smaller section joins the block with the + terminal of the battery.

[FirstOwner69]

It also served as the attachment point for the hot wire included with the optional camper harness. The wire was then routed along the top of the radiator support to the left inner fender. The wire then joined the other camper harness wires at the firewall. They were then routed rearward together.

It's the 10 or 12 gauge red wire in the pictures.

I don't know how this varied when the dual battery option was also ordered.

[54blackhornet]

Thanks for the explanation. Still don’t understand why they didn’t just insert a inline fuse instead of the fuseable link ?

[Grumpy old man]

Safety First Fusible link

You are most likely familiar with how a fuse works in an automobile, but here’s a quick reminder. A fuse serves as a link in your vehicle’s electrical system that can be broken under certain circumstances in order to protect various components and systems from damage. Typically, a fuse burns out when a circuit attempts to transmit too much current, severing the connection before the electrical charge can have any ill effects.

A fusible link acts much like a fuse, only it’s designed to handle a different type of potentially hazardous scenario. These links are actually strands of wire wrapped in a fireproof covering, and are thinner than the wiring harnesses they’re connected to. They are placed in-line between delicate harnesses and large sources of electrical current in your car—between the battery and alternator, for example. These links must transmit high-current electricity, but also protect the rest of the electrical system from dangerous spikes that could cause a fire. If there’s a surge, the link actually melts, as its resistance to heat is lower than that of the circuits it’s protecting. This cuts off power while protecting the engine bay from a conflagration, thanks to its fireproof wrapping.

When replacing a fusible link buy 2 and leave one in your glove box .

Never replace a fusible link with standard wire unless you like fires .

['68OrangeSunshine]

Originally Posted by FirstOwner69

It also served as the attachment point for the hot wire included with the optional camper harness. The wire was then routed along the top of the radiator support to the left inner fender. The wire then joined the other camper harness wires at the firewall. They were then routed rearward together.

It's the 10 or 12 gauge red wire in the pictures.

I don't know how this varied when the dual battery option was also ordered.

Hi Jim, I looked it up on the Google box. In the stock setting, yes, that red wire does cross to left and connect with the Pos terminal of the B battery. If there's an Isolater unit, a feed from A batt goes to one ternimal on the Iso and B batt to another, then a Red wire output to the Alternator, and connections to appropriate grounds, too.

[HO455]

Originally Posted by 54blackhornet

Thanks for the explanation. Still don’t understand why they didn’t just insert a inline fuse instead of the fuseable link ?

The fuseable link is a like a slow blowing fuse. In other words it will tolerate an over current condition much longer (relatively speaking) than a fuse will. Thus allowing high amperage current draw when starting the engine yet still protecting the vehicle from a direct short to ground.

[Big Kev-O]

Originally Posted by 72Thunder

Hi all,
i am confused by this as after everything cleared up we put it back on the fender and everything started up all fine and dandy. Is there something I'm missing?

Yes, you are missing a basic understanding of domestic 12v automotive wiring. I am not trying to be a jerk & this looks like this may be your first time dealing with automotive wiring so I will explain some basics to keep you from learning the hard way. Most American cars are designed with a NEGATIVE ground which means the entire chassis and every piece of metal bolted to it are connected to the negative terminal. Under no circumstance should you ever place a positive wire onto your chassis or anything metal. This will cause a short that will spark, melt wire and possibly start a fire if the circuit is not protected by a fuse. Most of the electrical components in your truck do not have negative wire that runs back to the battery because you can complete the circuit by grounding the negative wire to the chassis/body. For example your lights & radio have a positive wire coming from the fuse block through a switch and the negative wire is grounded to the chassis/cab. This is why you only see one negative cable leaving the battery.

[palallin]

Be careful--not ALL American cars had Neg ground. Go back to the '50s and earlier, and you will find Pos ground. Likewise, most Ag equipment prior to about 1960 had Pos ground.

[jabborabbo]

Originally Posted by '68OrangeSunshine

Sounds like you fried your old Fusable Link. That needs to be replaced with another similar length of same-gage fusable link wire.
My Dad had a '59 Jaguar that really did have a Positive 'Earth' System. Lucas Electrics. Now I know why the Brits drink warm beer... [Their fridge is broken].

I have several old Triumph motorcycles…the Brits were correct….

Technically, the current in a circuit travels from the negative terminal to the positive terminal (since that’s the path of the traveling electrons which are negative).

You can blame or credit Ben Franklin (who knew nothing about electrons, protons, etc.) for the Yankee definition of current flow from positive to negative.

[54blackhornet]

My 1967 MGB G/T was originally positive ground. Converted it to negative. Tossed the original positive ground radio for a blanking plate, and had to mod the tachometer. Still running the original generator to...

['68OrangeSunshine]

Originally Posted by jabborabbo

I have several old Triumph motorcycles…the Brits were correct….

Technically, the current in a circuit travels from the negative terminal to the positive terminal (since that’s the path of the traveling electrons which are negative).

You can blame or credit Ben Franklin (who knew nothing about electrons, protons, etc.) for the Yankee definition of current flow from positive to negative.

In his defence, Mr Franklin was making discoveries about a previously unknown force. One that had traditionally been attributed to the Divine. Chances of perceiving polarity were 50-50, especially at the end of a kite wire.
I worked in the Electrics shop on the early AV8A Harriers. Hawker-Siddeley and British Aerospace subcontracted with Lucas Electric for many system components. The Lucas Refrigeration gag was well known. As was the ''Prince of Darkness''. The aircraft had 2] 28 volt DC busbars w/ Negative ''Earth.''

[54blackhornet]

68 ! You are spot on ! Could not have summed it any more eloquently...

[Killer Bee]

1964 model E - positive ground

starter cable was a little short but got me by to get the old girl rolling again..

can't see the battery top but note the color of the clamps on charger leads

[Steeveedee]

Positive ground. In the Physics Department, we used "i" to define the current. In the Engineering Department, they used "j". Tastes Great, Less filing! When one gets to a junction and gets a negative current answer when applying Kirchoffs's rules, it simple means that the current is flowing in the other direction. That seemed to blow people's minds. I was in an engineering class (working on a master's degree, but dropped out because of my workload at my job) back in the '80s where the instructor drew an arbitrary curve and defined the current flow as "to the right" Then he said that -i was current flow in the other direction. Some of the student's heads pretty much exploded, at that point. By the time people took that class, they should have at least had vector calculus and differential equations, and gotten the significance of the sign change without a hiccup.

[body bolt]

Originally Posted by 54blackhornet

My 1967 MGB G/T was origi=nally positive ground. Converted it to negative. Tossed the original positive ground radio for a blanking plate, and had to mod the tachometer. Still running the original generator to...

Flash the field. Isn't that one of the first things one did to an LBC?