Some of this stems from the fact that the average person does not understand the importance of a ground. When a switch is turned on and current flows from a battery or alternator to its load those electrons have to get back to the negative side of the battery (I'm not going to go into does current floe from + to - or from - to + that's not really important for this discussion) If there is not a return path for electrons to flow is creates a voltage drop and loss of voltage, current and overall efficiency. The negative or ground side is equally as important as the positive side. Most don't look for or even consider looking for a ground path.
Also the fact that many devices either don't use a ground wire or also rely on the chassis of the load bolted to the metal frame which is grounded (we hope).
The best story (VERY TRUE) happened like this. My assistant principal came to me with an intermittent no-crank condition that had been going on for about 3-4 months. He had it in to 3-4 shops with no success. He had the battery replaced 3 times and had two alternators installed but would still get stuck with a no crank situation. We were studying this stuff so I went over it with the kids in class and put two on it. Within 5 minutes they came back with the problem diagnosed.
The negative battery cable connection to the block was loose. The engine would move on its motor mounts because of engine torque and it would not keep a good connection. They removed the bolt, cleaned the terminal, installed two clean washers and torqued the bolt. Problem solved.
TeJay
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TeJay Auto Instructor/4-yrs USAF/ Liz: RN/ WBGO 2014 Vista 30T/ F-53/CHF/5-Star/Koni * Bella & Izzy * Golden /Cocker mix/ Louie The Cat* All Retired
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