I did it and the same problem continues. I know it's not any wires picking up anything because I didn't move any wires except the ground in my following tests. First I took a laptop and made the connection using its battery, everything perfect. Then I took a the original ac connection that came with the computer and plugged it in to ac, and everything good except for a slight 60hz hum bar (nothing crazy). Then I took the original hook up, took the ground wire, ran it from the dcdc usb straight to the battery on the outside of the car, everything came back. I'm thinking the power line could cause this, but that doesn't make too much sense. Also, could the dcdc usb be the culprit? What next?
Also, I verified, I'm getting 13.7v steady, not moving or playing music. With base hitting I drop to 12.7-13v. I discoed the entire audio system, so there is absolutely no draw from the D block except the computer. And I took the ground straight to the engine block. Note, the ground that I used for this testing is two 16g wires.
The ground should not be the engine block - no vehicle/cabin loads use that; they'd use chassis/body (or fusebox) else the battery -ve.
The key is using the same ground, and separating low current ground (paths) from high current grounds.
After that, it's cross-grounding and induced noise problems.
I just read what I wrote, to clear up, I tested the ground (running on the outside of the car) to first the negative terminal and then to the engine block. The terminal caused the same problem. Sorry i wasn't clear before. And since the ground was on the outside, that would eliminate any induced noise pick up right? I also thought by going to the battery, that would automatically eliminate all ground loop and noise problems...not true?
If I discoed the power of the entire audio system, shouldn't that have eliminated the difference of high/low current ground paths? I assume (yes it's bad to assume) that the power draw from the amp and stuff would make the high, and that gone everything should even out, or at least get better.
So I guess I really have to go searching for the nav screens grounding point huh? If the problem is still there, what is cross-grounding and how do I fix it?
By cross grounding I meant what I call earth or ground loops - namely a loop connection of GNDs.
EG - a heavy GND from batt- to amp and a separate GND to the HU, and then an HU to amp interconnection that interconnects their GNDs. That is literally a loop.
Such gnd loops can be a PITA in domestic systems because they are prone to circulating currents from AC fields (eg, 50/60 Hz hum).
If you were like me, you would NOT expect the same in a vehicle because there is no "external" AC and a vehicle body may provide a lot of shielding. But "gnd loop" problems still occur because of gnd currents which cause equipment gnds to be at different voltages.
And then there is the noise - whether conducted or radiated - caused by changing currents and noisy DC lines.
And since there is lots of current switching occurring in a vehicle - whether it be their CPUs and digital equipment, dc-dc converters (PCs, mobiles, amps etc), inverters etc - there is lots of scope for line (DC) and radiated noise.
Hence why there are many solutions. HUs might be powered direct from the battery for "cleanest DC". (The battery is the biggest capacitor in a typical vehicle and does the most AC filtering.)
Heavy grounding (fat or short cables) may be used to reduce GND voltage drops. Single point or separate grounding for low current stuff like sensors and audio signals (ie, separate to power GNDs).
Breaking RCA shields/gnds at one end may break some loop problems, otherwise gnd isolators may be used.
So, by running your GND external to the vehicle, do you think you eliminated GND noise or caused more noise? (The answer would depend on your particular situation.)
Note that I don't consider myself anything of a GND loop expert - I'm just reciting some of the basics. (And my knowledge of noise suppression and shielding for analog transmitters etc is mostly irrelevant these days.)
Depends on vehicle...
Originally Posted by OldSpark
My Caprice had the ground running to the engine block. From the engine block there were 2 large ground straps running from the block to the frame. The frame then had large ground straps running to the body in different locations. At the battery the only ground was a very small 10 gauge wire that ran to the fender because the AM/FM antennae was mounted there. My Caprice was a police vehicle that had extra grounding straps installed and in all cases they were from the frame to the body of the car or from the engine block to the frame. I suspect that this is more the normal than exception especially with GM vehicles. If I disconnect the small wire from the battery that goes to the body I loose my radio reception and that is all. I believe they do this because of the fact the Starter Solenoid is incorporated internal to the starter thus making it much easier to run the ground through the engine block. I believe other GM vehicles I have had do this as well but I know for sure my Caprice does. I have had the engine in and out of this vehicle 3 different times.
Also, I still think your best bet may be to try a USB video card. It is relatively cheap and should isolate whatever problems you are having.
Another thing you can try is to use another battery as a test. Try duplicating your laptop test with your computer but using a separate battery to power the PC and see what happens. That will give you a better look at what is going on. Another car battery would be great but if you have a large 12volt battery you could use otherwise that should work as well. Just make sure it is fully charged. Then you can go from there to isolate your issue. If it passes this test your next step could be connecting the ground of the battery to your negative distribution block and see what happens.
So the starter motor and all electricals (when not charging) got their ground thru a 10G wire?
Originally Posted by redheadedrod
I find that somewhat difficult to swallow.
No... My car had two ground wires from the battery. The small 10 gauge wire to the fender was only for the antennae (as I mentioned in the message above if you read the whole thing...) The other was a 4 or 6 gauge wire that went to the engine block near the battery. My caprice has 2 braided copper ground straps that went from the back of the block to the frame. They actually connect to two of the transmission to engine bolts. Thus the block is used as a ground distribution system for the car.
The interesting thing with this was that it had two large +12V power wires as well. One went to the starter and the other went to the distribution block which I haven't had in other vehicles. The distribution block in this car also has a couple of taps for power directly off the distribution block that were full power connectors. You could use them to jump another car with or use it to tie your audio system to or whatever. I don't recall if the alternator went to the distribution block or if there was a third smaller wire that went to the alternator from the battery. Any other cars I have owned as far as I am aware have had a large positive wire that went to the starter and from the starter to a main fuse panel with a small 10 or 8 gauge wire running to the alternator from the battery. I always thought such a small wire was a bad idea but the length has always been pretty short.
Also I can't say if my other cars had ground systems like my caprice does. But I do not recall ever owning a car that I am aware of that had any other setup than 1 large ground wire going to the block. Some have had the small wire running to the fender but not all. And I didn't pay attention in the past to see if the small ground wire was always only for the radio reception. I have owned a couple fords and a chrysler mini-van otherwise all my other vehicles have always been GM's. I never tried to trace where the ground went to. I just happen to know in my caprice because I have taken 2 caprices all apart down to the bare frame and put one back together. The one I put back together I had to change the motor in a total of 2 times. First time because I didn't change out the water in the system to antifreeze before it got cold out and froze the block. Then the motor I replaced it with I used motor flush and it cleaned it too well and I spun a bearing on the car within 500 miles after I installed it. So swapped it again... Runs good now but I blew the transmission in it after 13000 miles on a rebuild.. (Damn burnouts.... Good thing the transmission had a 12000 mile warranty.. Sigh...)
You made it sound as if the only OEM grounding was the fender ground - ie, that by being a Police car it had the "extra grounding straps installed...".
And being a single battery Police car I can understand why the engine to body is considered more important than engine to battery-.
And I assume you have a single wire D+ type alternator and hence the battery connections are not that important (from a charging voltage POV).
The norm for most vehicles is a heavy GND from batt- to the block (for the starter) and a heavy GND between block & chassis/body with a 3rd often lighter GND from batt- to chassis/body, though the latter 2 can be interchanged (heavy from batt- to chassis and lighter from engine to chassis) or all 3 can be heavy. Some vehicles omit one of those GNDs. But the main requirement is that the batt- to starter GND and batt- to chassis loads can carry the starter and vehicle (body/chassis) loads respectively.
The hot side varies (excluding the heavy batt+ to the starter heavy terminal). The main +ve junction may be the batt+ or it may be the main fuse box or other distribution point. (The same can apply for the GND - eg, other than the batt- to starter GND, the main GND may be the main fuse box or other distribution point.)
Most vehicles that require ground planing for antennas (or grounding for other loads) merely run links to the chassis, though for antennas the same noise issues may apply as for audio power - eg, run direct to the battery.
Alternators almost always have their outputs (B+) straight to the battery, but newer vehicles (1970 onwards) often include a fuse and therefor may route through the main fused box etc. The wiring from the B+ (and its GND) need only be sized to suit the max alternator output
And non-D+ (two or more wire) alternators have their (thin wire) Sensing terminal direct to batt+, though again that is often through a fuse.
Ok so Oldspark you are confusing then...
In an earlier posting you said to not ground to the block because no one grounds through the block but here you are agreeing with me that vast majority of ground goes through the block. And I quote:
Originally Posted by OldSpark
So to ensure the best ground for a system requiring lots of power it would make sense to ground to the battery or the block. Either way should work. Although I would always suggest a larger than necessary wire running to the battery is always your best bet. And the mention that you need to make sure when you upgrade a ground that you upgrade all of the grounds. Figure out the route that the manufacturer took and upgrade all of the links. In this caprice I plan to add many more of the braided style grounding straps between the block and the frame. I COULD install a large ground cable from the battery to the frame rail directly or run a batter cable from the battery directly to my amplifier. But this is an example that if you just upgrade the OEM wiring you need to make sure you do it not just from the battery to the block (if that is your main connection) but also between the block and whatever body/frame ground it has. And if your car also uses the braided copper style grounding strap I would just add more of them to the vehicle instead of using a wire or you could just go from the battery to your location but it imperative to make sure all of the ground wires/straps from the battery to the location of use is of the proper size.
Originally Posted by OldSpark