# How to Properly Make/find a Ground



## worlddre (Oct 27, 2007)

Wrote this up for another forum and didnt see a thread for such things here so i figured it wouldnt hurt to add it here.

This is not going to be a long explanation as it is no at all difficult and for those who struggle with reading comprehension i am sorry there will be no pictures.

What to look for in a good ground

Look for a piece of metal that is apart of the vehicle chassis and not attached to the chassis with bolts or any other methods. For example in the 95-99 Mitsubishi Eclipses there is a little back hump against the back seat that looks like it would be an awesome spot to make a ground and many people and installers :sigh: make this mistake. In actuality this litle piece of metal is bolted to a painted part of the chassis and thus would royally suck as a ground. All in all make sure you are grounding to the unified chassis of the vehicle if not the frame itself. Also you do not need to ground to a factory bolt. While they are convenient if you cannot find one you can simply pick a location (preferably away for rear decks and the like) and attach a self tapping screw to it. Once your grounding location has been selected if you want to be sure you have selected good spot take a meter(DMM) and run a quick wire to the negative post on your battery (doesnt need to be pretty as it will be removed when you're done with it) and measure the resistance. If you can pick up any resistance with a commercially avaiblable meter you have selected a poor ground so try again.

How to prepare your well chosen ground location
This is simple, simply scrape away the paint at your chosen spot. This can be done using a variety of methods. The easiest method ive found is o take a drill and a wire brush attachment and have it until you can almost see yourself. Another method is to take a flat head screwdriver or a utility knife and have at scraping away. This method is not nearly as aesthetically attractive but works nonetheless. The final method is some very coarse grit sandpaper. I personally have never used this method but i cannot imagine it not working for any particular reason

How to prepare you ground wire
This also is very simple. *USE A RING TERMINAL.* If you do not have any at the time go to walmart or something and get some. They are not going to cost very much so there is no reason not to use one.

How to attach you ground
Also extremely simple. If you chosen ground location is a factory bolt (hopefully you made sure your ring terminal fits around the bolt) simply remove the bolt ,place it through your ring terminal and reattach it to the vehicle. Now if not using a factory bolt then simply inspect both sides of your chosen location. Make sure there are no gas takes or line running under the location you have chosen. Take the shortest available self tapping screw (usually 3/4") and screw it into the vehicle.

In closing this throught process is not only for amplifier installation. I use his thought process everyday when dealing with alarms and anything else i might need to find to ground.
the end

if i neglected anything someone please add it


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## khail19 (Oct 27, 2006)

One minor addition...

I would probably not use a self tapping screw for anything bigger than 12 ga wire, better to use a bolt, nut and lock washers for amp grounds.


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## worlddre (Oct 27, 2007)

Ive used both forgot to add that but i have yet to have a self tapper fail me not to mention due to the layout of many vehicles it is not really feasible to reach the underside of the chosen location to make use of a nut and blot


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## 8tz (Mar 6, 2008)

nice post.


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## FrankstonCarAudio (Feb 2, 2008)

khail19 said:


> One minor addition...
> 
> I would probably not use a self tapping screw for anything bigger than 12 ga wire, better to use a bolt, nut and lock washers for amp grounds.


X2

No way would I use a self tapping screw as a means of attaching a ground wire.
Get another person to help if you can't reach where you are grounding, to hold/tighten a bolt/nut with lock washers etc.
Self tapping screws always have a habit of loosening over a period of time, at least IMO.

Otherwise a good post...


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## t3sn4f2 (Jan 3, 2007)

worlddre said:


> Wrote this up for another forum and didnt see a thread for such things here so i figured it wouldnt hurt to add it here.
> 
> This is not going to be a long explanation as it is no at all difficult and for those who struggle with reading comprehension i am sorry there will be no pictures.
> 
> ...


Sorry, this is not correct. That method does not measure resistance under load. Find a good ground with your method and put a 10 amp fuse inline with it and measure again, still no rise in resistance right? But is it a good path to carry all the current the amps will pull? Nope. A bad ground can be seen like a under rated fuse on a proper gauge or chassis in this case.

Only way to check is to find a reference voltage under sine wave load using a proper gauge of cable that you know can carry the current you need to carry and then check for voltage drop compared to the reference using an accurate meter. No drop mean no added resistance under that current carrying condition.


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## worlddre (Oct 27, 2007)

if you could fully elaborate on that...that would be great even though i cannot edit the original post


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## t3sn4f2 (Jan 3, 2007)

worlddre said:


> if you could fully elaborate on that...that would be great even though i cannot edit the original post


Will try tomorrow, kinda late already.  

We discussed it a while back on the main general section, I can't remember the thread though but it was a lengthy one on the big 3 or something like that.


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## worlddre (Oct 27, 2007)

t3sn4f2 said:


> Will try tomorrow, kinda late already.
> 
> We discussed it a while back on the main general section, I can't remember the thread though but it was a lengthy one on the big 3 or something like that.


cool beans man i will hunt it down and give it a read


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## t3sn4f2 (Jan 3, 2007)

Found it, the whole thread has a lot of good inf. but this topic starts on post #78.

http://www.diymobileaudio.com/forum/showthread.php?t=29572&page=8&highlight=big


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## ErinH (Feb 14, 2007)

t3sn4f2 said:


> Sorry, this is not correct. That method does not measure resistance under load. Find a good ground with your method and put a 10 amp fuse inline with it and measure again, still no rise in resistance right? But is it a good path to carry all the current the amps will pull? Nope. A bad ground can be seen like a under rated fuse on a proper gauge or chassis in this case.
> 
> Only way to check is to find a reference voltage under sine wave load using a proper gauge of cable that you know can carry the current you need to carry and then check for voltage drop compared to the reference using an accurate meter. No drop mean no added resistance under that current carrying condition.


Basically, you have to assume your ground is correct to begin with. Then after you're ready to rock and roll play a pink noise, or sine wave track and check the resistance of that ground while playing your rig at some specified volume?

I must admit, I've been checking my ground the wrong way all this time. Though I have 0 noise, it's still very possible I do have resistance at my ground since I haven't checked using this method. Though, before then I checked and had 0.01ohms on my friend's $300 Fluke. :blush:


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## t3sn4f2 (Jan 3, 2007)

bikinpunk said:


> Basically, you have to assume your ground is correct to begin with. *Then after you're ready to rock and roll play a pink noise, or sine wave track and check the resistance of that ground while playing your rig at some specified volume?*
> 
> I must admit, I've been checking my ground the wrong way all this time. Though I have 0 noise, it's still very possible I do have resistance at my ground since I haven't checked using this method. Though, before then I checked and had 0.01ohms on my friend's $300 Fluke. :blush:


Your voltage not resistance.

There are gonna be things that affect the voltage reading slightly like a battery that can't provide continuous current at the level needed during the period of time that you are reading the voltage level. Leading to voltage dropping and making you think its a bad ground. Others thing as well. 

So the best thing to do is to install everything you can based on the right techniques and use this testing method to find a really bad grounding problem and nothing more really. Assume like you said it's OK after installing it and then check to see if the voltage drops drastically. If not then your amp is in its working range meaning you probably won't get a significant loss of wattage and definitely not an audible degradation of the sound. 

Plan for the worse and hope for the best.


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## Tirefryr (May 15, 2005)

Hope you don't mind, but I'd like to add a little something I do.

Once you've fully terminated your ground, cover it in a nice thick glob of silicone to prevent rust and corrosion, AND MAKE SURE YOU DON'T USE BARE ALUMINUM. It will instantly start corroding when toughing a dissimilar metal.


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## worlddre (Oct 27, 2007)

all additions are welcome


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## Richard (Feb 6, 2007)

Not being an electrical engineer, I was curious why the cables we use are copper while various battery terminals are not. For example, Knuconcepts, Stinger's cheaper line, etc. are made of zinc while more expensive lines are usually brass, which is 80% copper. The real budget terminals at the auto parts store are lead! However, my www. research shows that neither material conducts electricity as well as copper, which is why it's used in the cable. More research turned up 100% copper battery terminals by Moroso. My local supplier had the exact models under a different brand. I purchased the single battery terminal with a 4 gauge compression fitting for the ground and the double terminal with 4 and 2 gauge fittings for the positive. Single flat copper terminals at the other ends. Solder fittings are also available but I chose the compression type because of their simplicity and relative security. A touch of black weatherstrip sealant where the (slightly tapered) plastic cable jacket meets the terminal finishes the 20 minute job. Comments?

Richard


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## kknack (May 21, 2007)

I think they lean towards lead and brass more for longevity purposes. Copper has a tendency to rot depending on the conditions (NE US especially). In reality I doubt any of us leave our systems alone long enough for that to happen.


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## t3sn4f2 (Jan 3, 2007)

Richard said:


> Not being an electrical engineer, I was curious why the cables we use are copper while various battery terminals are not. For example, Knuconcepts, Stinger's cheaper line, etc. are made of zinc while more expensive lines are usually brass, which is 80% copper. The real budget terminals at the auto parts store are lead! However, my www. research shows that neither material conducts electricity as well as copper, which is why it's used in the cable. More research turned up 100% copper battery terminals by Moroso. My local supplier had the exact models under a different brand. I purchased the single battery terminal with a 4 gauge compression fitting for the ground and the double terminal with 4 and 2 gauge fittings for the positive. Single flat copper terminals at the other ends. Solder fittings are also available but I chose the compression type because of their simplicity and relative security. A touch of black weatherstrip sealant where the (slightly tapered) plastic cable jacket meets the terminal finishes the 20 minute job. Comments?
> 
> Richard


Like mentioned above, copper corrodes and even though tinned terminals of whatever material doesn't conduct electricity like pure copper does, it doesn't mean that they don't conduct its as good in those short distances when augmented by using more of that material (reason you see those BIG lead terminals and why you can ground to a hunk of poor conductivity steal frame).


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