How Many Grounds?

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All the OEM factory plus 4 that I always add.
Instrument cluster, radio case, rear tail light sockets, fuel gauge sending unit.
 
I have a battery to body , battery to block, block to the firewall using one of the voltage regulator bolts. I have one from the column to the dash frame, one from the fuel sending unit to the body , my rear tail light/head light harness to the body. my dash harness has a couple to the frame. I also use star washers with nuts and bolts to the firewall for my ignition box and the VR. ive also grounded my turn signal light housings to the body with separate wires. im sure im forgetting a couple.
 
grounds? well i just looked at my 1967 dart factory service manual. the electric, engine, body sections have NO pics of grounds. but we all know it does have some grounds.
 
The more the merrier. I usually go from battery ground terminal to radiator support. From radiator support to inner fender. From rear of the head to firewall. From where the ground cable connects to the engine to he frame rail.

All that said, there's a strange thing you can set up involving some kinda loop effect that boogers with the electrical system. I forget what it's called, but we've talked about it before. Maybe somebody with more tan half a brain will know what I am talking about. I cannot remember what it's called. But it ain't good.
 
jeffnmo said:
Ground loop?

Jeff
Click to expand...

That might be it. I know whatever it causes to happen ain't. I've seen crackedback talk about it before. Maybe either he or Del will chime in and ejeemakate me.
 
Just remember that for every ground, you will need a groundskeeper...
 
I will try to explain. A ground loop is an undesired current, in a conductor that is connecting two points in a circuit that are assumed to be at ground potential.

For those that want to escape the explanation, a ground loop is unlikely to cause a problem in a stock A-body. Why?. Because stock A-bodies do not have an ECU, or smart ignition module. Some call the 4 or 5 pin ignition box an ECU, but it is not.

If EFI, an ignition with smarts, AFR gauge, or an engine management system is installed, then there are great concerns for how for how connections to ground are made. I will call the prior, smart devices, that have a micro-controller. The smart devices make measurements and control things based on those measurements. Measurements are often made on sensors that are referenced to engine ground. Examples are temperature sensors, O2 sensor, knock sensors, and others. Some more modern sensors are two- wire isolated, and are isolated from the engine to avoid ground loops.

While adding or tying grounds together is a good thing, it is is also important to insure that the smart device share the same ground as the engine sensors. If it does not, sensor readings will be incorrect, resulting undesired control behavior under starting conditions.

A starter motor draws significant current. It can be as high as a few hundred amps in cold weather. While the battery cable that connects the battery to the engine block is large, it still has a voltage drop. The drop may be a few tenth of a volt, or even a volt or two. If a smart device is grounded at the battery, then there is a ground loop. The ground loop path, is the smart device supply ground connection and the sensor measurement grounds at the engine. The ground loop results an undesired current and voltage in the ground connections that parallel the battery ground cable. The undesired current, results in incorrect measurements, and possibly damage to smart device components, including burned printed circuit foils. By moving the smart device ground to the engine ground, the ground loop is eliminated.

If you are curious about voltage drop on the negative battery cable, use a voltmeter while cranking, black lead at battery terminal, red lead on engine ground.
 
In my 65 Dart, I used the battery and alternator cables from a 90's Dodge truck that I took the mini-starter from. The neg cable had several flying ground leads, in addition to the thick block lug, so I ran ones to main frame, radiator support, and a terminal just for the headlamps. I ran dedicated returns for the headlamps, rather than rely on the sheet-metal screws the factory used.

I have found to never trust a ground thru aluminum. Once I had a Dart alternator stop working, and the problem was simply a bad ground thru the aluminum case to bracket. Another time, in my M-B, the speedometer cable started smoking when I cranked the engine. They ground the starter thru the aluminum tranny case and the strap connections had corroded, so the speedometer became the return path.
 
KitCarlson said:
I will try to explain. A ground loop is an undesired current, in a conductor that is connecting two points in a circuit that are assumed to be at ground potential.

For those that want to escape the explanation, a ground loop is unlikely to cause a problem in a stock A-body. Why?. Because stock A-bodies do not have an ECU, or smart ignition module. Some call the 4 or 5 pin ignition box an ECU, but it is not.

If EFI, an ignition with smarts, AFR gauge, or an engine management system is installed, then there are great concerns for how for how connections to ground are made. I will call the prior, smart devices, that have a micro-controller. The smart devices make measurements and control things based on those measurements. Measurements are often made on sensors that are referenced to engine ground. Examples are temperature sensors, O2 sensor, knock sensors, and others. Some more modern sensors are two- wire isolated, and are isolated from the engine to avoid ground loops.

While adding or tying grounds together is a good thing, it is is also important to insure that the smart device share the same ground as the engine sensors. If it does not, sensor readings will be incorrect, resulting undesired control behavior under starting conditions.
Click to expand...

Exactly. This is why most modern vehicles have a separate sensor ground or sensor return that is wired directly back to the control unit. That sensor return is isolated internally in the control unit and is typically approximately 1/2 volt higher than chassis ground. This is to prevent electrical noise on the ground plane from inductive electrical devices such as ignition coils, a/c compressor clutch coils, fuel injectors, etc. from interfering with the sensor signals.

A starter motor draws significant current. It can be as high as a few hundred amps in cold weather. While the battery cable that connects the battery to the engine block is large, it still has a voltage drop. The drop may be a few tenth of a volt, or even a volt or two. If a smart device is grounded at the battery, then there is a ground loop. The ground loop path, is the smart device supply ground connection and the sensor measurement grounds at the engine. The ground loop results an undesired current and voltage in the ground connections that parallel the battery ground cable. The undesired current, results in incorrect measurements, and possibly damage to smart device components, including burned printed circuit foils. By moving the smart device ground to the engine ground, the ground loop is eliminated.

If you are curious about voltage drop on the negative battery cable, use a voltmeter while cranking, black lead at battery terminal, red lead on engine ground.
Click to expand...
 
BillGrissom said:
They ground the starter thru the aluminum tranny case and the strap connections had corroded, so the speedometer became the return path.
Click to expand...


Seen that before a couple of times, and one that was grounding through the U joints.
They brought it to me because they were replacing U joints once a month and not trashing on the car at all. ( like neutral drops and stuff like that)
The arching of the current from the caps to the U joint journals via the needle bearings was eating up the bearing surfaces.

Figure that one out without ever seeing it before. :D
 
BillGrissom said:
I have found to never trust a ground thru aluminum. Once I had a Dart alternator stop working, and the problem was simply a bad ground thru the aluminum case to bracket. Another time, in my M-B, the speedometer cable started smoking when I cranked the engine. They ground the starter thru the aluminum tranny case and the strap connections had corroded, so the speedometer became the return path.
Click to expand...

I really agree with all that about aluminum and magnesium. I play with older VW and Porsche, I have found even with using a heavy star washer and 10mm (about 3/8") bolt on a ground cable to a magnesium transmission case, it is possible to have an open connection. It is necessary to remove the invisible layer of anodization.
 
TrailBeast said:
Seen that before a couple of times, and one that was grounding through the U joints.
They brought it to me because they were replacing U joints once a month and not trashing on the car at all. ( like neutral drops and stuff like that)
The arching of the current from the caps to the U joint journals via the needle bearings was eating up the bearing surfaces.

Figure that one out without ever seeing it before. :D
Click to expand...

If someone says there car runs like crap, or dies when they are off the gas, it is sometimes indicates an open or loose engine to body ground. Giving it gas squeezes the oil in gears and bearing resulting in electrical conduction. It is hard on all the bearings. The mopar hidden ground strap going from head to firewall is often forgotten.
 
..............my 67 dart gt also had a ground strap from the fire wall to the hood from the factory....thanks for the lessons guys, just made me a little wiser today.......kim....
 
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