OT: Automotive ground strap question
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    Default OT: Automotive ground strap question

    Doing some preventative maintenance on a 2001 GMC Yukon. So the braided ground strap from the firewall to the engine looks pretty "green" and I'm going to replace it since apparently a bad ground can cause all kinds of hard to solve electrical issues. My question is: why is the strap braided and not a nice insulated piece of stranded cable?

    Thanks.

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    The braids supports higher amperages, greater heat dissipation, and dependable performance when there's linear movement, lateral motion, or repeated vibrations.

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    There is no point in having a ground insulated.

    You can buy good quality braided ground straps for cheap, so for the average vehicle there's no benefit in reinventing the wheel.

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    Quote Originally Posted by GregSY View Post
    There is no point in having a ground insulated.

    You can buy good quality braided ground straps for cheap, so for the average vehicle there's no benefit in reinventing the wheel.
    Just to throw some fuel on the fire..

    how about "Coated" to prevent corrosion?

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    Quote Originally Posted by GregSY View Post
    There is no point in having a ground insulated.
    Other than an insulated cable with properly sealed ends won't degrade over time until it starts causing hard to diagnose electrical problems! Just watched a video of a guy whose Chevy van would die periodically. The dealer replaced the ECU, no change. Then the fuel pump, no change. Finally the owner figured out it was the braided ground strap.

    Yes, it is a cheap part and will probably last longer than the vehicle will. While I'm at it I'm going to clean the connections on the other grounds and the battery terminals. I hate electrical problems.

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    They usually ARE coated. The silverish look is often from tin, which is resistant to many common corrosive materials, and is plated on the srands to resist corrosion.

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    Quote Originally Posted by JST View Post
    They usually ARE coated. The silverish look is often from tin, which is resistant to many common corrosive materials, and is plated on the srands to resist corrosion.
    I thought they were galvanized.

    Sent from my SAMSUNG-SM-G891A using Tapatalk

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    Quote Originally Posted by 52 Ford View Post
    I thought they were galvanized.

    Sent from my SAMSUNG-SM-G891A using Tapatalk
    That one made me laugh. Are you a "standup comic" ?? :-)
    ...lewie...

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    Just for the record, galvanizing usually refers to dipping in molten zinc, which in this case, would have resulted in a rigid bar. People often refer to zinc plating as galvanizing which it is not. Zinc plating is done in electroplating tanks. JST is correct. Most copper that is coated is coated with tin.
    Braided copper cables are seldom used these days as it is not mechanically protected and cost more to make than insulated cable. It is better when there is a lot of vibration and flexing. A good automotive application would be bonding the engine to vehicle frame.

    Tom

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    Bonding the engine to the frame?

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    Quote Originally Posted by kustomizingkid View Post
    Bonding the engine to the frame?
    Electrical definition - not a mechanical bond, but an assurance that there's uniform and sufficient electrical continuity between objects.

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    Cable implies a grouping of multiple conductors, separated with insulation. Only a single conductor is needed for the ground strap so cable is overkill. The real question is braided strap vs. stranded WIRE.

    As far as I can see, the only real current that will flow between the engine block and the chassis is that needed for the generation of the sparks. This will be in pulses as each spark plug fires with rest periods between them. Perhaps heat is a concern, but I suspect that resistance is much more of one. Any resistance here would produce a Voltage drop from the 12V battery Voltage and that drop would cause a weaker spark unless the circuitry provides against that. But even that would have it's limits so a good, low resistance connection is needed and is probably the less expensive alternative.

    As for braided strap vs. stranded wire, both are used when motion and vibration would eventually cause a solid wire to fail due to metal fatigue from repeated flexing. And if the total cross section area of copper (or other conducting material) is the same, both braided and stranded should provide the same resistance. The choice of one over the other is likely due to more mundane issues, like the cost of terminating the ends. A piece of stranded wire would be round and would need some form of termination, probably crimped terminals on the wire ends or electrical screw style terminal blocks on the engine and frame. A piece of braided strap can have a hole drilled or punched in the end and a simple bolt and washer would then be used to fasten them to the block and the frame. A quick dip in a solder pot before creating that hole will prevent those ends from fraying. A self tapping screw with a drill tip would eliminate two more steps in the process for even greater economy. All of that can cost less than applying a crimped terminal or using terminal blocks. On top of that, crimped terminals or terminal blocks also add two more potential points of failure between the wire and the terminals. So the braided strap without terminals is more reliable.

    Since you are not Ford Motor Company or GMC or Toyota and do not have an army of bean counters looking over your shoulder, you can feel free to use the twisted, stranded wire with the appropriate terminals. I would apply some form of corrosion protection after fastening the ground wire in place. Properly installed, it should last just as long.



    Quote Originally Posted by SteveF View Post
    Doing some preventative maintenance on a 2001 GMC Yukon. So the braided ground strap from the firewall to the engine looks pretty "green" and I'm going to replace it since apparently a bad ground can cause all kinds of hard to solve electrical issues. My question is: why is the strap braided and not a nice insulated piece of stranded cable?

    Thanks.

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    Quote Originally Posted by Milland View Post
    Electrical definition - not a mechanical bond, but an assurance that there's uniform and sufficient electrical continuity between objects.
    And not to be confused with grounding.

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    If you are talking about grounding like in a house or building where there is an actual ground rod, no it is not a ground.

    Since a typical vehicle sits on four or more rubber tires, which are very good insulators, there is nothing in it that is actually grounded. Nor is there any need for that except at toll booths where the toll collectors do not want to be the path for static discharge. Ouch!

    The engines in most vehicles are mounted on (synthetic) rubber mounts and are electrically isolated from the frame/chassis. But the Ignition system is usually/often mounted on the engine due to the need to time the sparks to it's rotation. The battery usually has it's negative terminal connected directly to the frame/chassis so the return path for the 12 Volts that operates the ignition system must have a return path and that is provided by a wire or mesh strap connection to the frame where the battery negative is connected. It is easy to see how a bad connection between the engine and the frame could cause strange performance problems.

    So, yes it is an electrical connection, not a mechanical one. But I do not think it could be called a ground. "Common" or "battery negative" or "return path" would be better terms.



    Quote Originally Posted by Cole2534 View Post
    And not to be confused with grounding.

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    And all these years I thought it was all about keeping your speakers from crackling from static electricity.

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    A tremendous amount of current flows when the starter & solenoid are operating. Corrosion at the ground strap connects increases the resistance and can cause a large enough voltage drop so that the solenoid cannot stay engaged.

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    A high traffic GM shop should have caught the bad ground strap quickly. GM vans have a handful of known issues and the GS is one. Along with overheating connector terminals in the fuel pump circuit.
    Joe

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    Insulation on wire won't stop it from oxidizing. Many an old demolished wire I've stripped to find it's entire length oxidized from end to end. You can't rightly seal a stranded wire against moisture ingress unless you completely immerse both ends in No-AlOx or equivalent. Even so it doesn't make a lick of difference for the wire itself. It's the connection that is vulnerable.

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    Quote Originally Posted by Just a Sparky View Post
    Insulation on wire won't stop it from oxidizing. Many an old demolished wire I've stripped to find it's entire length oxidized from end to end. You can't rightly seal a stranded wire against moisture ingress unless you completely immerse both ends in No-AlOx or equivalent. Even so it doesn't make a lick of difference for the wire itself. It's the connection that is vulnerable.
    Is No-AlOx suitable for copper wire?

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    Quote Originally Posted by EPAIII View Post
    Cable implies a grouping of multiple conductors, separated with insulation. Only a single conductor is needed for the ground strap so cable is overkill. The real question is braided strap vs. stranded WIRE. ..............
    Well, when I install a battery in an automobile I attach battery cables and when I help someone get their car started I use jumper cables, each having one conductor. This here is America, so if you want to call them something else, go ahead.


    Quote Originally Posted by Just a Sparky View Post
    Insulation on wire won't stop it from oxidizing. Many an old demolished wire I've stripped to find it's entire length oxidized from end to end. ...........................
    Yes, I can see where insulation is so old and degraded that it no longer protects the copper from oxidation. I can also see on 15-20 year old vehicles where frickin' mice have gone around doing taste tests of the wiring insulation that the copper underneath looks fine and is FAR better than the braided ground strap which is so oxidized it's green.


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