The Importance of Automotive Grounds

Whether it is a racecar, the RV or your daily ride, the grounding system is as important, if not more important than the positive side of the battery. In fact if we go back to the 40’s, 50’s and early sixties, we would find that some production cars used the idea of positive grounds but it actually doesn’t have any impact on how the car operated. The ground still needed to be good and solid.


My first encounter with a defective battery ground cable in a vehicle was a 1989 Ford truck. I came out of work only to find that the engine would turn over but very slowly and not enough to fire it up. After breaking out the volt-ohm meter and doing some checks, I finally realized that the ground cable connection had loosened at the engine block and corrosion had built up between it and the metal of the block. Doing a quick cleanup with a screwdriver got enough of a ground to start the truck and once I was home, I did a better job of correcting the issue.

Not starting is certainly one of the major warnings that you have a problem going on, but even as the problem is building to that point, you might experience some poor performance that is so minor that’s it is hardly noticeable. In today’s cars, if you take a closer look – grounds are everywhere. The electronics require extremely good grounds but as in all systems, they can be improved. Anything that you do to provide an additional ground path or improved grounding of the current path is a huge benefit. And if the grounding was starting to fail, you might actually see an increase in performance or mileage.

RVs are especially prone to poor grounding of the various systems. Understanding that when an RV is built, you have a chassis that is supplied to the RV builder that is basically a running chassis with a steering column. The RV builder then adds the RV package to this chassis and of course the quicker you build it and get it out the door, the faster you see your money. For an eye-opener, just check the grounding that you are going to find on the connections to your headlights, fog lamps and taillights as these are commonly part of the RV package. Now you might understand why the headlights on your RV are not exactly the brightest and heaven help you if you decided to upgrade your lamp wattage. If you haven’t suffered some melted wiring, you probably will and the main reason is the poor grounding.

Race cars, especially those that are built at home are another source of poor grounding practices. The bottom line here is that a lot of hot rodders know how to make it go and stop pretty good, but ask them about the wiring on the car and more than likely they paid someone to wire it or a good friend wired it for them. Wiring is a mystery to most of them. And the grounding of some of the systems that are used can get downright complicated if not done correctly.

So – how to properly ground something? Well, first off let us always remember one very important fact. If we decide due to the item that we are wiring that we need a 14 gauge wire to connect the battery or positive side, then we need a 14 gauge ground wire too. Will it operate with a 16, 18 or even 20 gauge wire? Yes it will, but will we get all of the performance from it that we expect – no we will not. Try to think of the wiring in a circuit in it’s basic form. We need a complete circuit or loop – like traveling from our home to the grocery store – we also will need to travel from the grocery store to our home. We have to be able to return, completing the loop. As we travel to the store, we have a roadway that is more than adequate in size for us to travel, but what if the roadway was only half the size on our return trip home? Our return path will slow us down. So again if we want the best performance from any item or device we power, we need to have a corresponding ground of the same size. Our grounds need to made to a solid return path to the ground side of the battery. In our vehicles, we normally use the metal chassis as a ground plane – connecting to it and in turn the negative side of the battery. But there are cases where we should consider nothing less than a solid return to the battery itself or at least a specialized extension piece connected to the negative side of the battery. Our connections should be clean of any residue, rust or corrosion. In areas that are exposed to road conditions, we should consider applying a no-ox type compound once all of the connections to that ground point are made. No-Ox compounds can be normally found in the electrical departments of the big box stores or an electrical supply house. Grounds need to be checked from time to time to ensure that they remain clean and tight. At the first sign of performance degradation – check your grounds first!

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