GROUND WIRE QUESTION....................

I am hearing a lot of rules about electricity that are misused. Sounds like a few to many conversations at the bar.

It doesn't matter which way the current flow is. Cut your + or - cable and insert an ampmeter. The current is the same anywhere in that series circuit. So yes running a 2 gauge + with a 4 gauge - leaves you with a 4 gauge circuit.

We run very low voltage high current stuff at work. If I told you some simple rail circuits and how they worked you would say no way. I'm telling you WAY.

A mild steel car with good welds will carry electricity just fine as long as the connections are good. But, usually they are not. Flat washers don't penectrate and make a good connection. I cut and fix old junk all the time. There are a lot of welds that will not carry electricity well. Don't know how the car stayed together either. CHROME MOLY has trouble carrying electricity. It has carbon in it just like resisters.

My recommendation is run a #4 welding cable from the battery to the engine. Then go from that to a bulkhead. From bulkhead to the body and chassis in as many ways as possible. Use grounding washers otherwise you are pissing in the wind. I have a grounding lug on my chrome moly cage. It is just a conveneint connection point.

If you have concerns about how well a peice of tubing or any steel can carry electricity use an ohm meter and check it. For a better test. Take a 55watt headlight and run copper wires to it from your battery fully charged. Take a current reading. Then unhook the negative wire and hook to your chassis. Take another current reading. If the current is the same and the battery voltage was the same. Guess what, your car is fully capable of carrying electricity.

If you want to run big ground cables and ground busses with plenty of bonding wires it will not hurt a thing. Grounds are good. Better to be well grounded than not. There are many cars with limited grounds that do just fine. The more electronics you have the more you need good grounds.

Leon
22 years of Signal Maintaining and Signal Electronic Specialist Norfolk Southern Corp.

Good info, thankxxx...........

Add one ground cable from the torsion bar crossmember to the starter stud and all is well.

Mine is torsion bar crossmember to trans. Eliminates water pump,motor plate, and block. 1 gauge, 6" long
Doug

I have been driving around on the street for 10+ years with a battery in the trunk and the negative cable is bolted to a stud on the rear frame rail. The electrical system in my car works flawlessly. Electric fan, MSD 7AL2, lights, etc. Clean grounds with some type of anti-corrosion good will give you years of service.

For what it's worth I did a voltage drop test today. I turned on both fans and measured the drop on both the positive side and the ground side. The positive side was higher than I would have liked at 1.32 volts. My fan relay feed is wired directly to my alternator stud. There is only a #8 to the battery for the alternator so this may require a rework. However this was with the car not running. Anyway the ground side which consists of 6" #1 cable from battery to cage, 6" #1 from the torsion bar crossmember, transmission bolted to the engine, engine bolted to the motor plate, ground for the fan at the plate. The ground side voltage drop was .03 volts. Though not completely scientific it show the ground side to be more than adequate for a fairly strong amp draw. I didn't have an amp meter handy to measure but I would guess 25 amps + for the pair.
Doug

I am a Spaghetti Menders dealer/installer and I firmly believe in Bob Lapp's "floating ground" system. Does it add some weight? yes, but I will take the piece of mind of a properly operating electrical system vs. a few pounds.

Here is some info from the Spaghetti Menders website, please excuse the way it is written. He tried to use some humor by using his dog Noodles as the author.

"Hi my name is Noodles I'm the inventors helper - I do all the leg work. My job this week is to let you know that all the electricity used in your car needs wires to get from the battery to all the devices you operate.

But the wires are just one of many things that need to be rated for the devise you will be operating. You will have a switch for turn on and off the devise. A fuse is for protecting the wire from damaging your car if the load is higher then the switch or wire can handle. Some times a relay is used if the load is higher then the fuse or switch can operate.

So now that you are confused I can shed some fleas on the problem, The biggest thing I see is that the ground is not installed right, yes the ground wire that hooks to the car frame. When cars where first made in the 1920 they used the car body as ground to save money on wire and half the labor to install (1 wire) for each device, Now it's 2005 and you wired your race car that way and your fuel pump and fans don't work right and you keep burning up switches and blowing fuses and you can't find any shorted wires but it keeps on doing it and you lose the race.

Back to the wires when power from the battery go's to the switch then to the device you turn on ( fuel pump - fan etc. ) it has to get back to the battery ground to make it work, but if you put anything in the path that is not able to handle the load before or after it you can make the fuse blow. Yes I barked at you about bad grounds can blow a fuses. All the power needed to operate your fuel pump and fan has to start at the battery and end at the battery so anything that slows down the power will give you an itch you can't scratch. So the best way not to have problems is to make sure you have the shortest path from battery to the fuel pump and back to the battery that's where relays come in they are remote switches it's by your pump and needs a small amount current (the power that makes things work) to operate and can switch high current like fuel pumps and fans.

So now we have the shortest route from battery to fuse to relay to pump back to battery with wire sized for the current draw of your pump. The best way to size your wire is to go one size bigger than they supplied under 6 feet,Two sizes bigger over 6 feet. The fuse is there to keep high current draw like a shorted wire that rubbed through on sharp piece metal or your pump that shorted out from heat. That's the only need for a fuse to stop the fire when the wire gets to hot from to much current. Now the switch that's mounted by the dash only has to power the relay at 1/4 of a amp draw less then a small light bulb that means very small wires and switches can operate fuel pumps and fans.

Now back to grounds if the power goes through a wire to your pump it has to go through the ground wire to the battery not the car frame, rust that you can't see and steel is not as good a wire as copper. Now this wags my tale, if you have copper wire on your fuel pumps power supply and you hook the ground to the frame what ever is lost in going through steel is felt in the pump because it's like a hose if you stand on one end, the water only flows the amount that get by your foot. So no matter where you put your foot the flow slows down. It's the same with wiring your car, if you slow it down by using steel as your ground, it makes it harder to operate and can blow the fuse and not having a shorted wire, you can slow down your pump making it work hotter and then burn up."

Speaking of computers, let me throw in the term "Peremeter ground" Anybody know what that means?

Isn't that Perimeter Ground? Used to prevent static and surge damage.

Spegetti Menders must not understand E equals I times R. I am sure that is not the case but when reading this that is the conclusion most EE's would come up with.

A high resistance circuit does not blow fuses. It actually limits current. Take 10 volts to make the math easy. 10 divided by 10 ohms (9 ohms load or appliance plus 1 ohm for your copper feed and ground) That is 1 Amp. Now take 20 ohms. (9 ohms load or appliance and .5 ohms for your copper feed wire and 10.5 ohms in your old Mopar chassis) That's 1/2 Amp.

Spagetti menders knows copper grounds are better they just don't seem to state why correctly for every type of load or appliance. A bad ground does not blow switches and fuses necessarily. A light bulb will only light based on the voltage at the light bulb. An electric motor or anything with inductance on the other hand will act much differently. MIke brought up spagetti menders and they do have some really nice stuff but all auto electronic providers recommend good grounds for the same reason. I hope not to bore you guys to death with what follows that should help explain.

Without getting into mho or J factors and get everyone including myslef thoroughly confused a good ground is never a bad thing. If everything is done correctly a chassis ground works. Star washers, clean welds, and good steel. Sorry anyone who has ever tig welded on Mopars knows the metal is a little funky. So if you run good ground wires from engine to battery you are not wasting any weight or money. And to all your equipment especially including relays and the MSD.

Why would a bad ground burn up switches, fuses, and appliances? A bad ground is never just a bad ground. It comes and goes. So back to resistance in the circuit. When it comes and goes so does the current flow. Well some appliances are very demanding like a spinning fan. Start making and breaking the circuit like a bad kid with your light switch in your home and something is going to give. Your home has at least a 15 AMP breaker so the switch and bulb is usually first to go. On a car the trouble is much harder to find.

Industry leaders are just trying to save you a lot of trouble and recomend running grounds to elliminate these failed circuit possibilities and phone calls trying to find bad circuits in your car.

Race car wiring has come a long way. I know service trucks use the frame for a ground and there is always something malfunctioning and it is 90% of the time ground related. So I am not going to criticize anyone for running grounds on a race car. Just their reasoning. LOL

Leon

I know service trucks use the frame for a ground and there is always something malfunctioning and it is 90% of the time ground related. So I am not going to criticize anyone for running grounds on a race car. Just their reasoning. LOL

Leon

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Big trucks the frame is rivided together which under
stress/load and time come loose creating a bad ground
joint so yes thats not good