i have a question for you guys. now, believe it or not, my knowledge of electricity is very limited, despite all the installations i've done in my car. i've always thought you need power and ground cables both connected for a unit to work. so up until now i've always had both cables connected carefully.
long story short today i needed to figure out of all the cables i've got grounded, which one was the one for the rear view camera, and i ended up unplugging all cables at once, and still every single thing turned on!

my in-dash nesa tv only had the 12+ cable connected and it turned on. the navigation's ground cable was unplugged too, and it came on the rear view camera, the video amplifier, the headrest tvs, the only thing that did not come on when i unplugged the ground cables were the neon lights

can you guys give me a simple explanation as to why all my electronics worked without being grounded?

btw, everything was grounded back again:-)

 

Like you, I am not into auto electronics. A lot has changed in the last fifty years, but it may be that some things are still somewhat similar. If so, an experience I had long ago might still apply. Or not.

I remember making a trip from Maryland to Arizona in the 1950s. At that time, cars used generators instead of alternators to create electric power and recharge the battery. But I think the principles are the same for your situation.

In a nutshell, the car caught fire under the hood three times while I was enroute. The problem was that the ground cable was broken. It was inside an insulating sheath, so the break was not visible.

The result was that the voltage regulator, sensing the battery was draining, was telling the generator to recharge the battery. So the generator ran full-tilt, but, because of the broken ground, was not able to get juice to the battery. So the overworked generator kept overheating and catching fire.

I bought three batteries, three voltage regulators and three generators on that trip. It took an analysis by an astute mechanic in Tucson to find the problem.

But the point here is that every electrically operated accessory on the car worked fine the entire trip. Had the fires not began, the battery would eventually have drained completely, at which point everything electrical would have failed.

This may be your situation. Most things work, but without a ground, the alternator cannot recharge your battery, and it would eventually drain, and everything would quit working.

But then everything may be totally different today. In the 1950s, I would have bet tires would never work without inner tubes.

 

In a typical situation electronics will not turn on without a ground. For all of those to work I might think you had a weak ground through the screws holding them into the dash/frame, etc...

 

Good call.

I will add not just typical. IT WON"T STAY TURNED ON WITHOUT A GROUND!
Therefore, you still have a ground path maybe not just a good one.

In order for current to flow there must be a path. Without ground there is no path. Imagine a perfect ground as a zero resistance path. But there are virtual/resistive ground paths as well through screws and what-not.

The more current/power the better the ground needs to be. Guage of wire and length goes a long twords the quality of the ground. I guarantee if you disconnect your ground from your battery with the engine turned off you will have nothing to see or hear---so there is a ground path.

A lot of times car manuals will have you disconnect the negative/ground of the battery terminal first. The reason being touching ground/negative battery terminal isn't going to get you shocked or cause sparks to fly. If you touch the positive terminal you can still have a "virtual" ground-therefore a path for current flow through your body or the wrench touching something(not good).

I know this is technical but this is the best explanation I could find about generators and alternators...
The key difference between an alternator and a generator is what spins and what is fixed. On a generator windings of wire (the armature) spin inside a fixed magnetic field. On an alternator, a magnetic field is spun inside of windings of wire called a stator to generate the electricity. This allows the wires to be directly and easily connected to their outputs without the need for sliding contacts to carry the relatively high output current. The magnetic field is still generated via electro magnets mounted on a rotor, and the relatively small field current that powers them is supplied to the rotor by two small brushes that each ride on a separate and continuous slip rings. These smooth slip rings (unlike the comparatively rough contacts on a commutator in a generator) and the fact that the relatively heavy windings are fixed instead of rotating allows the alternator to be spun to much higher speeds. This allows it to reach it's maximum output sooner and to be spun fast enough at engine idle speeds to produce enough electricity to power most (if not all) of the needs of the car without relying on the battery.

Another key difference between early generators and alternators is early generators produced DC by using what is called a commutator, versus alternators producing AC that must be converted to DC using what is called a rectifier.

Sorry if this isn't very clear but it's the best I could do. Maybe someone else can explain it better.

 

I will second what was said by CoolMax. Basically the equipment itself was in someway grounded. Most electrical equipment has its chasis/frame whatever grounded, hence if any bit of this metal had contact with any other metal(ground) in your vehicle then VIOLA, a ground path would be present. Not a good ground, but a ground none the less.

 

see that's what i thought too, but after looking for like 20 minutes i saw no way of it being grounded. like i said, the in-dash tv had no connection whatsoever to any metal, it's held on to the plastic bezel with velcro and then like i said, the cable was unplugged. the video amplifier too. maybe the camera and navigation had some sort of ground somewhere along the line, but i dont see how the other two things i mentioned did

anyways, it's good to be grounded right? i'll keep it all grounded for now, then one of these days i'm going to take everything down and watch the cables from beginning to end...thanks for the help guys

 

YES, Grounding is good. Please ground everything. It's a must, despite the fact that it's working.

 

In reading posts subsequent to mine near the top of this thread, I would guess the ends of my broken ground cable must have been barely touching inside the sheath, but not in good enough contact to carry a full charge to the battery.

 

Thanks for the info.