Team Camaro Tech banner

1 - 17 of 17 Posts

·
Registered
Joined
·
35 Posts
Discussion Starter #1
On the negative battery post of my 69 a smaller wire branches off the main negative cable and is bolted to the wheel well.
I am asuming this is a ground.

Is it really needed?
 

·
Registered
Joined
·
486 Posts
Yes, it is a ground. Leave it in place. It was a factory design grounding area and these cars need good grounding to keep the electricals in tip top shape.
 

·
Registered
Joined
·
46 Posts
This "little" ground wire literally provides the ground path for the entire car. It's not only needed, it needs to be carefully inspected as mentioned above to ensure a good connection.

The big (-) battery cable is only meant for a ground path for starting the car and the ground path for the alternator's charging. All lights, electronics and accessories ultimately get a connection to the body itself and the fender ground provides the path back to the battery.
 

·
Moderator
Joined
·
20,096 Posts
Since I moved my battery to the trunk I lost that wire....but I do have a few strategically placed to make sure I have a good ground :yes:
 

·
Premium Member
Joined
·
263 Posts
Does anyone have a pic of where the ground wire should be? I am swapping in new cables and battery and my old one had the ground wire running to the radiator support. The new cable pigtail won't reach that spot (or the headlight ground) so I'd like to drill a hole in the correct spot and get it connected as it was originally intended. Thanks
 

·
Registered
Joined
·
142 Posts
Mine goes to the vertical lip on the inside of the fender, a few inches behind the battery and below the hood.
 

·
Registered
Joined
·
6,246 Posts
This "little" ground wire literally provides the ground path for the entire car. It's not only needed, it needs to be carefully inspected as mentioned above to ensure a good connection.

The big (-) battery cable is only meant for a ground path for starting the car and the ground path for the alternator's charging. All lights, electronics and accessories ultimately get a connection to the body itself and the fender ground provides the path back to the battery.
The battery cable to the block is also the ground for the ignition system, all the switches and senders on the block, any electrical function that uses the block as a ground. You will be well served to run a well connected ground cable from the block to the firewall, which will improve the electrical operation of your dash items. Depending on a single ground to the fender can bite you.
 

·
Registered
Joined
·
46 Posts
The battery cable to the block is also the ground for the ignition system, all the switches and senders on the block, any electrical function that uses the block as a ground. You will be well served to run a well connected ground cable from the block to the firewall, which will improve the electrical operation of your dash items. Depending on a single ground to the fender can bite you.
While you are correct that the main battery negative also provides the ground for ignition and block-related components, I think you have missed the point of my over a year-old post. Everything that is not engine block ground related is grounded to the vehicle body. The vehicle body is connected back to battery (-) via the "little" 12 ga. wire mounted to the fender.

This is standard GM practice. Grounding the firewall is pointless. Dash components are grounded to the dash frame, then the firewall and ultimately the body.

The only reason some cars have engine to firewall ground straps is for RFI suppression for radio equipment. They are NOT mean to provide current paths.

You will never have issues if you truly understand the GM design and maintain it. People go too crazy with adding grounds in hopes of solving issues with substandard repairs, or worn out original equipment.
 

·
Registered
Joined
·
6,246 Posts
While you are correct that the main battery negative also provides the ground for ignition and block-related components, I think you have missed the point of my over a year-old post. Everything that is not engine block ground related is grounded to the vehicle body. The vehicle body is connected back to battery (-) via the "little" 12 ga. wire mounted to the fender.

This is standard GM practice. Grounding the firewall is pointless. Dash components are grounded to the dash frame, then the firewall and ultimately the body.

The only reason some cars have engine to firewall ground straps is for RFI suppression for radio equipment. They are NOT mean to provide current paths.

You will never have issues if you truly understand the GM design and maintain it. People go too crazy with adding grounds in hopes of solving issues with substandard repairs, or worn out original equipment.
If everybody stuck with the standard GM practice of the 1960's we'd be in trouble here. Stock cams, 700x14 tires, drum brakes, points/condensers, etc.

Explain to me how RFI suppression occurs without current flow? I started working on radar in 1965 so I'm familiar with RFI, but I've never seen it work unless you had current flow. Why are these non-current flowing 'ground' straps made of a fairly substantial braided cable? If you hook them up, how do you keep them from flowing current? If you hook them up and your electrical problems are diminished, do you remove them to revert to the 'standard' GM practice then spend a buttload of money trying to figure out where your grounding problem is? I don't think I would.
 

·
Registered
Joined
·
7,160 Posts
If everybody stuck with the standard GM practice of the 1960's we'd be in trouble here. Stock cams, 700x14 tires, drum brakes, points/condensers, etc.

Explain to me how RFI suppression occurs without current flow? I started working on radar in 1965 so I'm familiar with RFI, but I've never seen it work unless you had current flow. Why are these non-current flowing 'ground' straps made of a fairly substantial braided cable? If you hook them up, how do you keep them from flowing current? If you hook them up and your electrical problems are diminished, do you remove them to revert to the 'standard' GM practice then spend a buttload of money trying to figure out where your grounding problem is? I don't think I would.
This is what I do:

The way I do it is run a common 10 gage wire for ground to all the ground points you wish to have grounded via one wire with soldered joints and covered with shrink. I then run that to the block and battery. In simple terms I have complete separate ground harness. I have yet to redo the system in my 67 since getting her back on the road last year but when it was there before over a period of many years and over 150,000 miles it worked very good. I always had bright lights, hardly ever blew a fuse and I had the same battery all that time and went through one alternator and it was working fine the bearings just gave out. In fact I had that same battery in the car until just a month or two ago. I think if the system is working well the other items that go with it will also work well and be trouble free. Not much help on your RFI question....sorry.
 

·
Registered
Joined
·
46 Posts
If everybody stuck with the standard GM practice of the 1960's we'd be in trouble here. Stock cams, 700x14 tires, drum brakes, points/condensers, etc.

Explain to me how RFI suppression occurs without current flow? I started working on radar in 1965 so I'm familiar with RFI, but I've never seen it work unless you had current flow. Why are these non-current flowing 'ground' straps made of a fairly substantial braided cable? If you hook them up, how do you keep them from flowing current? If you hook them up and your electrical problems are diminished, do you remove them to revert to the 'standard' GM practice then spend a buttload of money trying to figure out where your grounding problem is? I don't think I would.
Yeah, it's a good thing GM doesn't practice your its own sage wisdom..... Unlike radar technology and tire technology GM grounding systems have NOT changed very much in the last 50 years. My 2000 Chevy I ordered new is set-up the same as a 1969 Chevy. 2 battery grounds. One directly to the engine block and one to the body. No engine to firewall straps.

Take a look at an assembly manual sometime. You know where you find the "firewall straps"? Try UPC 12, under RPO U63 and U69. Guess what? Subtitled "radio suppression".

Take a look at a virgin original "radio-delete" vehicle. Guess what? No factory straps.

Try to find a TSB (technical service bulletin) that specifically states for service techs to "inspect" the braided suppression straps when the customer complains of hard-starting or dash instrumentation issues. Good luck with that.

Ever see a new old stock radio kit that the dealer would have on a shelf to install a radio? Guess what's in there? The straps. Guess what? No mention that the straps are there to "help with grounding the electrical system of the vehicle". Because that is NOT what they are for.

Why so "thick". Does it really matter? Where are the typical mounting mounting points for these straps on the engine? Valve cover bolts you say? Let's see, last I checked the torque for those bolts is not 40 lb-ft! Something that is just "snug" isn't going to safely carry large current amounts. They are thick because they had to be braided flat to give them enough composition to hold up with the heat, vibration and jerking of the engine under load. That is why there is no insulation on them as well, that would have quickly melted and deformed being "draped" where they are.

I'm not going to respond any more to this thread. It's simply foolishness when people suggest to start adding grounds from engine to frame and firewall when they have issues with their electrical systems. Add all you want, but people just don't understand the GM design. Only 2 main grounds are needed. One to the block and one to body to handle the current demands of the vehicle.

The only reason there are problems with something built in 1965 or 2005, is there is a lack of understanding (I see it all the time on many GM message boards) of how the system is MEANT to work, so the components aren't properly maintained and then they fail OR are not restored properly during reassembly.

Done.
 

·
Registered
Joined
·
7,160 Posts
I would think that the single 12ga wire attached to the fender with a sheetmetal screw would be adequate for the current demand with factory accessories. Add elec fans, big stereos, high intensity headlights etc. and I would think it becomes inadequate.
You would think correctly....aircraft, missiles and missile systems all have a separate ground systems or dedicated wiring and ground because it's a better way to go but cost more. I am going to trust a system built for reliability over one that is built for cost reduction. Save 50 cents on auto manufacturing and multiply that by 6 million vehicles built and you just put that money in the pocket of the company.

People can post about what works and how foolish it is to add to it and be asinine about it as has been posted here. While others post alternative ideas that improve the system. GM built all this stuff to make money and if you don't think the bottom dollar was not engineered (industrial engineering) into any of their products then your the foolish one.


"Done" l:)
 

·
Registered
Joined
·
6,246 Posts
A couple of points:

Electricity takes the path of least resistance, so it will flow through any conductor with a path back to the source. It doesn't care whether the engineer thought it was supposed to carry only high frequency components, or what it says in some old tech bulletin, current will flow through these cables. On an engine with the alternator internally grounded to the block, all the current in the active system returns through the block to the alternator. Any draw on the alternator, i.e. lights, fans, radio, fuel pump, etc. requires a return path to the alternator, which is firmly grounded to the block. Gotta remember Kirchoff's current law. It's not the chassis that is ground, it's the case of the alternator that's ground. All current goes back to the grounded side of the bridge in the alternator.

As most of the cars at this site are nowhere near stock electrically, with added fans, pumps, big thumping stereos, air conditioning, halogen lights, etc, most of them have upgraded their alternators. One of the cardinal rules of high current alternators is larger wiring, and nobody scrimps here. Put the 8 gauge wire from the alternator to the distribution block, but you're supposed to keep the 12 gauge single ground wire from the fender to the battery to the block? No wonder you have problems.

In 1965, a 37 amp alternator was sufficient to run the system, I'll bet you can't buy a car today with less than a 100a alternator, and I'll also bet that the ground wire isn't 12 gauge.
I don't know what you were driving in 1965, but I'll bet the radio was AM as FM receivers weren't very good then. One of the problems with amplitude modulated signals is that they are very susceptible to noise, as in RFI. RFI doesn't bother strict DC devices, like fans and lights, you can't hear it and you can't see it. If you have a device in your car that actually looks for radio frequencies, it will find the RFI and amplify it through your speaker. There was no need to add really good grounds to the cars unless they had radios, and who here doesn't have a radio?

It doesn't take 40lb/ft of torque to make a good ground, and I'll bet that the valve cover bolts are more robust than the screw used to attach the ground cable to the fender. Just because the box the ground cables came in doesn't specifically say "better ground", there's no other effect except a better ground. They, by any means of circuit analysis, will carry as much or more current to the block as the 'system' ground. It's the laws of physics.

You put a nice pair of braided copper cables in parallel with the stranded 12gauge wire, and the braided cables will conduct more current, and more high frequency current because of the skin effect.
 

·
Registered
Joined
·
648 Posts
Just as a note, electricity doesn't flow back to the battery via the ground! Electricity flows from negative to positive. THis was the FIRST thing GM drilled into techs heads when we were required to take Specialized Electronics Training (SET). This was what began our understanding of GM electronics and how they work. Funny Techs no longer have to take this course. Guess that's why so many are stupid....atleast at my dealership
 

·
Registered
Joined
·
6,246 Posts
The prevailing circuit analysis schemes use what is called 'conventional' current flow, which has the effect going from positive to negative, except in the current source, where it goes from negative to positive.

Another interesting aspect of electric current is the speed at which the current actually flows, i.e. the actual movement of electrons. If you had a 1 meter long 18 gauge wire conducting 3 amps DC, it would take about an hour for an electron to travel the length of the wire.

In your house, powered by AC, you use the same electrons over and over.
 
1 - 17 of 17 Posts
Top