# grounding amps to chassis not ideal?



## Lightninghoof (Aug 6, 2006)

Someone over on ICIX posted the comment:

"Using a chassis ground is about equivalent to a 4 gauge wire. If you were pulling a lot of current and using a power wire thicker than 4 gauge, you will decrease resistance by running a dedicated ground (same size as power wire) from battery to the amps."

I have been studying car audio for several years as a hobbyist and have never heard anyone make the claim that it is better to route the ground from the amplifiers all the way back up to the battery due to the chassis only being the equivalent of a single 4-gauge run of wire.

Any truth to this statement?


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## t3sn4f2 (Jan 3, 2007)

Lightninghoof said:


> Someone over on ICIX posted the comment:
> 
> "Using a chassis ground is about equivalent to a 4 gauge wire. If you were pulling a lot of current and using a power wire thicker than 4 gauge, you will decrease resistance by running a dedicated ground (same size as power wire) from battery to the amps."
> 
> ...


Chassis metal path from say the trunk floor to the battery terminal can have a few non conductive bridges between them, it the - terminal is grounded to the frame there could be rubber body mounts between things, body panels could be glued together in newer cars thanks to adhesive bonds being just as strong as metal welds these days. 

Just get a thick cable that you would use and measure it with you meter to get a reference resistance and then use that cable to measure the resistance from the trunk to the batterry post. By using that thick cable you will not have to worry about the thin long leads of the meter affecting the results.


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## Vestax (Aug 16, 2005)

Lightninghoof said:


> Someone over on ICIX posted the comment:
> 
> "Using a chassis ground is about equivalent to a 4 gauge wire. If you were pulling a lot of current and using a power wire thicker than 4 gauge, you will decrease resistance by running a dedicated ground (same size as power wire) from battery to the amps."
> 
> ...


Makes no sense to me. Why would you want to waste all that effort and money? Only way to prove it is to measure the voltage drop between both set ups. I highly doubt you'll gain anything from doing it that way.


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## MarkZ (Dec 5, 2005)

It's very vehicle-dependent.


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## JAG (May 6, 2006)

MarkZ said:


> It's very vehicle-dependent.


This is a VERY correct statement ! In my testing , almost ALL of the instances , a large ga wire will have less resistance , and will be less likely to allow noise on the ground.


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## chad (Jun 30, 2005)

I think it's BS, if the welds are good, which they usually are and the frame/body grounds are in tact a peice of sheetmetal TRUMPS a 4 ga wire for grounding.

Chad


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## 89grand (Nov 23, 2006)

chad said:


> I think it's BS, if the welds are good, which they usually are and the frame/body grounds are in tact a peice of sheetmetal TRUMPS a 4 ga wire for grounding.
> 
> Chad


Yeah, that's exactly how I feel about it. All that sheet metal is less than a 4 gauge wire? I seriously doubt it. 

They're all about big wire over there it seems.


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## JAG (May 6, 2006)

chad said:


> I think it's BS, if the welds are good, which they usually are and the frame/body grounds are in tact a peice of sheetmetal TRUMPS a 4 ga wire for grounding.
> 
> Chad


Then buy yourself a shop , measure it on probably 30 different cars ( like I have ) , and THEN reply back with an informed response , and not just a guess.


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## ghart999 (Feb 8, 2006)

I have measured the voltage drop from about 10 points on my chassis versus a 00 gauge wire and found that they are extremely close. Hence for my situation, running a ground wire would've been a waste of time and money. For reference, I have a 02 Grand Prix (4dr).

On the other hand, a friend of mine has a Nissan pickup. We did the same test and found that a 00 gauge wire had less voltage drop than the chassis, so we used a ground cable for his vehicle. The statement of "Its vehicle specific" is exactly true. Until you do an actual test yourself you will never know for sure which is better.


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## fredridge (Jan 17, 2007)

How about a boat??? 

we ended up buying 2 install kits so we could run wire to ground.


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## MarkZ (Dec 5, 2005)

*If* the welds are good. Not true for all rustbuckets.

I'm curious how you all are measuring the voltage drop. Does your ohmmeter resolve that fine? Or are you actually measuring vdrops, and under what conditions?


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## Vestax (Aug 16, 2005)

fredridge said:


> How about a boat???
> 
> we ended up buying 2 install kits so we could run wire to ground.


For a boat, it makes more sense, especially if the boat chassis is not conductive. For a car, the ground plane is much larger, this is why most people would believe it would have no problems completing the circuit. Well I guess the guys were right, it depends on the vehicle. Although, it would be too anal for me to do it that way. 

I would say for practicality, ground it to the chassis.
For perfection, wire it up back to the battery with a bigger awg wire.


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## bobduch (Jul 22, 2005)

I'll buy vehicle dependent. On my old 1990 Bronco we grounded all the amps and xovers in the back to the right side frame rail that ran all the way up front. No noise. Grounding to metal by amps had some noise. That was of course a chassis on frame vehicle. Now most are unibody.
When in doubt, measure.


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## 1stOnRaceDay (May 30, 2007)

fredridge said:


> How about a boat???
> 
> we ended up buying 2 install kits so we could run wire to ground.


Another problem with using the hull (if conductive) is that you will set up galvanic corrosion and chew through your anodes very quickly. Once you're finished with them the hull goes. I've seen aluminum boats taking on water through the holes in the hull.


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## thehatedguy (May 4, 2007)

You are assuming the unibody cars have welded panels...a lot of newer cars have chemically bonded panels with minimal tack welds.


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## durwood (Mar 7, 2007)

I would believe it could be possible but they only true way to tell would be to actually measure the voltage drop under load. No way are you going to be able to measure the resistance drop on something like that with a standard DMM. You would need a milliohm meter that is capable of meaursing anything under ~1 ohm. Even a dead short on most DMM's will still read 0.7-1 ohm. I'd like to see some real world measurements. Any one care to try and post it up?


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## biggerrigger (Jan 14, 2007)

All things aside your chassis ground is only going to be as good as the negative cable from the battery to the chassis. If its dirty where it mounts to the frame or corroded or small in size then you are going to have problems. I have seen this to many times where people will upgrade there power wire to the largest size they can get but pay no mind to the ground side of the circit and wonder why $300 worth of wire and fuses and distro blocks did nothing for there system. This goes for electronic sensors on the engine as well. " I just replaced A $150 gonkulator on my 1984 mormon missile and it only lasted a month and its allready bad again whats wrong with these parts" Its 9 out of 10 times a bad ground. People will check and double check that the plug on the sensor is clean and tight but look past the other end of things thinking that since its a big hunk of metal it has to be a good ground. Its only as good as the small piece of rusted/oil soaked/loose/dirty/small gage wire that connects that big hunk of metal back to the battery. I allways tell people to upgrade there ground before they do anything else. It has solved many problems that people think are power related. If your lights dim upgrade the ground. If you have noise in a system upgrade the ground. If your amps dont make the power that they did in your buddys car upgrade the ground. If your gonkulator only last a month upgrade the ground. This is the most overlooked connection in a automobile and can cause the most problems. 
"When in dout Ground it out"
Aaron


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## biggerrigger (Jan 14, 2007)

Sorry about the spelling Im still asleep
Aaron


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## t3sn4f2 (Jan 3, 2007)

biggerrigger said:


> All things aside your chassis ground is only going to be as good as the negative cable from the battery to the chassis. If its dirty where it mounts to the frame or corroded or small in size then you are going to have problems. I have seen this to many times where people will upgrade there power wire to the largest size they can get but pay no mind to the ground side of the circit and wonder why $300 worth of wire and fuses and distro blocks did nothing for there system. This goes for electronic sensors on the engine as well. " I just replaced A $150 gonkulator on my 1984 mormon missile and it only lasted a month and its allready bad again whats wrong with these parts" Its 9 out of 10 times a bad ground. People will check and double check that the plug on the sensor is clean and tight but look past the other end of things thinking that since its a big hunk of metal it has to be a good ground. Its only as good as the small piece of rusted/oil soaked/loose/dirty/small gage wire that connects that big hunk of metal back to the battery. I allways tell people to upgrade there ground before they do anything else. It has solved many problems that people think are power related. If your lights dim upgrade the ground. If you have noise in a system upgrade the ground. If your amps dont make the power that they did in your buddys car upgrade the ground. If your gonkulator only last a month upgrade the ground. This is the most overlooked connection in a automobile and can cause the most problems.
> "When in dout Ground it out"
> Aaron




A great simple way to check that contact is proper between power connections is to touch that part where you want to be sure of when the music is playing for a while and the car is cold, you will feel it heat up if the metal to metal contact is not tight and in pretty bad situations it will be burning hot.


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## chad (Jun 30, 2005)

.


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## durwood (Mar 7, 2007)

I think all this grounding all the way to the battery is another marketing ploy to get people to buy/sell mroe wire. I'd like someone to prove that a car is completely glued together and welds are no longer used.

I guess all the other ground sensitive computer and other wires must need to be run all the way back to the battery too.


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## chad (Jun 30, 2005)

AVI said:


> Then buy yourself a shop , measure it on probably 30 different cars ( like I have ) , and THEN reply back with an informed response , and not just a guess.


So I take it you ground back to the battery?

BTW I have installed WAY more than 30 grounding systems involving sheet metal. And tested their current carrying capacity with the motha of current producing devices, .. Lightning.... Multiple times... each time it storms, coming from a tower 400' in the air or more. Guess what? It gets the current from point a (the sky) to point B (the radials) with amazing efficiency. Strap is the best way to ground, sheetmetal is a big strap. And I have plenty of information on this to prove my education on it if you would like linkage/white papers.

And I trust you did these measurements with a milliohm meter? I would be interested in seeing the results BEFORE the grounding from the battery ot the chassis.

I also trust that you FUSE this extra ground cable that you run, you know the virtues of this correct?

Chad


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## durwood (Mar 7, 2007)

biggerrigger said:


> All things aside your chassis ground is only going to be as good as the negative cable from the battery to the chassis. If its dirty where it mounts to the frame or corroded or small in size then you are going to have problems. "When in dout Ground it out"


Yep. This is overlooked so much. A good ground must be clean and free of paint, dirt, rust, grease, etc...and use a star washer if you have one, it's a great investment. And I regularly check my grounds overtime for build up of rust or corrosion.



t3sn4f2 said:


> A great simple way to check that contact is proper between power connections is to touch that part where you want to be sure of when the music is playing for a while and the car is cold, you will feel it heat up if the metal to metal contact is not tight and in pretty bad situations it will be burning hot.


Another good point. Seen that recently. A coworker I sold my old kicker amps too was complaining he was blowing fuses. I go look and quick inspections revealed a melted fused holder followed by a piss poor ground. Gues what cuased the fuse holder to melt? (Proper gauge wire was used from my inspection).


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## thehatedguy (May 4, 2007)

Durwood, go ask a body shop about how unibody cars are put together these days. The sheet metal panels are not competely welded, but spot welded and seam sealer spread on the rest. Some cars with aluminum panels are glued together using panel adhesives.

Because you can't believe something doesn't make it true.

Also, talk to the hardcore SPL guys especially the ones in the Street classes who are limited to battery size and number without upgrades to alternators...see how many of them are grounding their amps straight to the chassis vs how many are running mulitple power and grounds back the the battery (multiple meaning 6-7 runs of 1/0 each). Then ask them why they get a higher SPL number with the increased number of grounds...amp is making more power that's why. How is it making more power? Less voltage drop.


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## thehatedguy (May 4, 2007)

Why would you fuse a ground?


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## durwood (Mar 7, 2007)

thehatedguy said:


> Durwood, go ask a body shop about how unibody cars are put together these days. The sheet metal panels are not competely welded, but spot welded and seam sealer spread on the rest. Some cars with aluminum panels are glued together using panel adhesives.
> 
> Because you can't believe something doesn't make it true.
> 
> Also, talk to the hardcore SPL guys especially the ones in the Street classes who are limited to battery size and number without upgrades to alternators...see how many of them are grounding their amps straight to the chassis vs how many are running mulitple power and grounds back the the battery (multiple meaning 6-7 runs of 1/0 each). Then ask them why they get a higher SPL number with the increased number of grounds...amp is making more power that's why. How is it making more power? Less voltage drop.


But they are spot welded in more than one place. I was just pointing out that it is welded even if it spot welding and not held together entirely with glue. There are rare cases, yes, aluminum, carbon fiber, fiberglass, but MOST cars are ok with using the chassis ground. 

As far as SPL, that is in an extreme case. Yes I have seen it, and most of those installs are ugly and serve one purpose- a burp. Burping is not music--at least to most people.


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## chad (Jun 30, 2005)

thehatedguy said:


> Why would you fuse a ground?


In case the stock ground has more resistance/fails. It's fine and dandy to have the amp grounded, I don't argue with that but if the stock ground were to fail the amp ground would act as ground.... via the head unit chassis and RCA cables. Things get hot very fast. 

It's VERY common to run RF gear grounding back to the battery at which point a ground fuse is required for fire reasons. Granted the fuse will be huge and the signal lines will probably melt anyway but it is common practice.


So.... what if one were to do this.... Run a solid ground line back from the battery to chassis and star ground the amplifiers to the bond of the chassis and the new line. This may help in ground loops (since we ARE talking about ground potentials here.) And other noise related issues. I'm totally open to the idea, I'm just not open to someone telling me a peice of sheet metal cannot carry an INCREDIBLE amount of current. But then we have the bonding issue.

Glad I have no intrest in SPL 

Chad


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## durwood (Mar 7, 2007)

a big 3 upgrade would serve a greater purpose then running ground wire to the battery, but again in most cases, it's not completely necessary unless you are in need of lots of power, which in my definition is anything greater than 1000W.


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## durwood (Mar 7, 2007)

thehatedguy said:


> Why would you fuse a ground?


What about those who beleive in the "other" theory of current flow of low to high instead of high to low? 

Chad's explantion makes more sense, but I thought I would throw it out there.

Added: I don't fuse my gorund wire before someone tries to flame me.


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## fej (Feb 8, 2006)

Well, considering that the only metal in my car is a small section of frame beneath the car which bolt the seats in place, and the front and rear "crossmembers" for the engine and suspension cradles, and the aluminum block ... I still have zero noise or grounding issues with a fiberglass car. I don't run grounds back to the battery, I have always used a single location less than 18" in length from a ground block or the amp location itself. If I continue to have issues I will upgrade the factory grounds .. and 99% of the time the issues are gone. I generally even use the factory ground for aftermarket HU wiring and still do not have noise/power issues in all but 1 of my 25+ installs. (And I think that one was a bad HU)

I do however agree with using slightly larger cable in the grounds than may be "recommended". If it calls for 8 I use 4, calls for 4 I use 2 gauge etc. My truck install is getting 1/0 power and ground .. overkill for sure but more cable makes for easier travel.


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## fej (Feb 8, 2006)

Well, considering that the only metal in my car is a small section of frame beneath the car which bolt the seats in place, and the front and rear "crossmembers" for the engine and suspension cradles, and the aluminum block ... I still have zero noise or grounding issues with a fiberglass car. I don't run grounds back to the battery, I have always used a single location less than 18" in length from a ground block or the amp location itself. If I continue to have issues I will upgrade the factory grounds .. and 99% of the time the issues are gone. I generally even use the factory ground for aftermarket HU wiring and still do not have noise/power issues in all but 1 of my 25+ installs. (And I think that one was a bad HU)

I do however agree with using slightly larger cable in the grounds than may be "recommended". If it calls for 8 I use 4, calls for 4 I use 2 gauge etc. My truck install is getting 1/0 power and ground .. overkill for sure but more cable makes for easier travel.


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## exmaxima1 (May 31, 2007)

durwood said:


> Added: I don't fuse my gorund wire before someone tries to flame me.


I won't flame you---I applaud you.

Fusing the ground wire makes absolutely no sense in a car. Any fuse just adds series resistance, and there is no fire hazard in a car from a ground wire.

I'm only a BSEE, so maybe someone with an MSEE can trump me on this one...

Matthew


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## solacedagony (May 18, 2006)

exmaxima1 said:


> I won't flame you---I applaud you.
> 
> Fusing the ground wire makes absolutely no sense in a car. Any fuse just adds series resistance, and there is no fire hazard in a car from a ground wire.
> 
> ...


Chad explained in post #27 why, in this situation, you should use a fuse on the ground.


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## MarkZ (Dec 5, 2005)

chad said:


> In case the stock ground has more resistance/fails. It's fine and dandy to have the amp grounded, I don't argue with that but if the stock ground were to fail the amp ground would act as ground.... via the head unit chassis and RCA cables. Things get hot very fast.


I don't get it. 

If the HU ground fails, what will fusing the amplifier ground do?


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## durwood (Mar 7, 2007)

exmaxima1 said:


> I won't flame you---I applaud you.
> 
> Fusing the ground wire makes absolutely no sense in a car. Any fuse just adds series resistance, and there is no fire hazard in a car from a ground wire.
> 
> ...


Yes, I agree. more voltage drops equals more strain which equals mroe problems.



MarkZ said:


> I don't get it.
> 
> If the HU ground fails, what will fusing the amplifier ground do?


I think what he means is that if for some reason the chassis is no longer grounded, anything elctrical in your car will try to use the amplifer's ground point and everything will feed back through your audio system. Has this ever happened that anyone has seen???


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## chad (Jun 30, 2005)

MarkZ said:


> I don't get it.
> 
> If the HU ground fails, what will fusing the amplifier ground do?


Because the starter would derive ground in this order Battery-> Amplifier -> signal lines -> headunit -> chassis

Dem starters pull some juice. In this case one MAY be running a dual post battery, if the stock negative built up resistance, especially one that would not deal with the back EMF of the starter well then issues would ensue.

Yes a starter makes back EMF... Put your fingers across the battery terminal and you don't feel anything right? While they are there have a buddy just tick the starter and tell me the expression you end up with on your face  

Chad


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## chad (Jun 30, 2005)

durwood said:


> Has this ever happened that anyone has seen???



Yes, kinda... I saw a starter ground rot away and the starter try to derive ground from the ****ty 12Ga "chassis ground" on a stock electrical system. It caught on fire.


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## exmaxima1 (May 31, 2007)

solacedagony said:


> Chad explained in post #27 why, in this situation, you should use a fuse on the ground.


Yeah, he explained it---but it made no sense. What he said is that if the main ground fails, then the amp will use the signal ground for its power return. And by fusing the MAIN ground, somehow this alleviates it. 

That's what makes no sense. If you believe this is a typical situation (BTW, I'm not of this persuasion), then fusing the ground open will only force the amp to find another ground path. In this case it would make more sense to fuse the HU ground. If you are worried about the main ground failing, you run ANOTHER ground in parallel. You don't fuse it!

In hospitals, institutions, and most commercial plants, it is required to run an additional ground wire JUST IN CASE THE MAIN GROUND PATH (typically the conduit) FAILS. That's the green wire you find in a cord. When I wire up some machinery, I pull a additional green wire through every conduit all the way to the fuse panel just in case somehow the conduit is broken (say, by a fork lift) and the ground is breached.

If the chassis ground is of limited integrity, I would run a heavy UNFUSED ground wire back to the battery terminal. That way the primary ground is always the path of least resistance, and let the power lines blow fuses.

Matthew


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## durwood (Mar 7, 2007)

chad said:


> Yes, kinda... I saw a starter ground rot away and the starter try to derive ground from the ****ty 12Ga "chassis ground" on a stock electrical system. It caught on fire.


I could understand that, but I thought you were refering to the main vehicle ground wire, if you lose that I could see all sorts of bad stuff happening.

The worst thing I saw was the main BIG fuse in the stock fuse panel was loose and caused poor connection. Then the stock fuse panel melted and almost caught fire. :O Again though this was the positive, not ground.


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## chad (Jun 30, 2005)

exmaxima1 said:


> Yeah, he explained it---but it made no sense. What he said is that if the main ground fails, then the amp will use the signal ground for its power return. And by fusing the MAIN ground, somehow this alleviates it.
> 
> That's what makes no sense. If you believe this is a typical situation (BTW, I'm not of this persuasion), then fusing the ground open will only force the amp to find another ground path. In this case it would make more sense to fuse the HU ground. If you are worried about the main ground failing, you run ANOTHER ground in parallel. You don't fuse it!
> 
> ...


Woah, that's a safety ground! Different ground, it's designed to provide high current back to the neutral bus so that if there is line voltage on the chassis it will pop the breaker. 

Big difference, the ground in a car the SOURCE of the current flow, it is TO BE a current carrying medium.


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## MarkZ (Dec 5, 2005)

chad said:


> Because the starter would derive ground in this order Battery-> Amplifier -> signal lines -> headunit -> chassis
> 
> Dem starters pull some juice. In this case one MAY be running a dual post battery, if the stock negative built up resistance, especially one that would not deal with the back EMF of the starter well then issues would ensue.
> 
> ...


Is the amplifier the only thing in a car that's grounded through the chassis though? I've seen all sorts of things grounded that way in my car. Remove the amplifier ground, and the starter would just try to ground through something else.


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## chad (Jun 30, 2005)

MarkZ said:


> Is the amplifier the only thing in a car that's grounded through the chassis though? I've seen all sorts of things grounded that way in my car. Remove the amplifier ground, and the starter would just try to ground through something else.


Exactly, so you have a thick cable running to the engine block by the starter, and then off the battery post along with that you have 1 or more smaller wires (in a stock rig) off to the chassis correct?

Chad


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## fej (Feb 8, 2006)

Just a guess but it is likely the starter would look for the amplifier ground being that it is the largest gauge and the path of least resistance in relation to the factory 10-20 gauge ground wiring in most cars. Seems logical to me /shrug


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## thehatedguy (May 4, 2007)

No, in a car there is no reason to fuse a ground wire. I still don't follow the logic...been messing with car audio for 15 years, did it professional for 5, and compete my own personal car...and fusing a ground wire only adds a weak link to the ground.

If it were a problem...why aren't there fuses or fusible links on grounds from the factory? In all of my days under the dash and hood of a car, I've yet to see one of those.


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## thehatedguy (May 4, 2007)

Even when the amp ground is 12 foot away and the factory ground is less than 5? Um...



fej said:


> Just a guess but it is likely the starter would look for the amplifier ground being that it is the largest gauge and the path of least resistance in relation to the factory 20 gauge ground wiring in most cars. Seems logical to me /shrug


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## durwood (Mar 7, 2007)

I'd like to repeat my statement from some time ago:

Has anyone actually taken a milliohm meter and measure the resistance on chassis ground to the negative of a battery and then again on a 15-20ft piece of 4 gauge or larger wire? I want to see some numbers.


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## MarkZ (Dec 5, 2005)

fej said:


> Just a guess but it is likely the starter would look for the amplifier ground being that it is the largest gauge and the path of least resistance in relation to the factory 10-20 gauge ground wiring in most cars. Seems logical to me /shrug


But how would it get access to that ground? Through the RCA's? That's not very low resistance.

I'm not ashamed to say it -- I still don't get it.


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## chad (Jun 30, 2005)

MarkZ said:


> But how would it get access to that ground? Through the RCA's? That's not very low resistance.
> 
> I'm not ashamed to say it -- I still don't get it.



In some instances the sheild is bonded to chassis, like my alpine for example, shield ids chassis ground. Which in turn goes to the AC that is using the grounded input. So it would melt the signal cable just fine along with the internals of both probably.

Really, the simplest way and CORRECT IMHO if you don't want to fuse the ground and as I said things will still melt due to the current rating of the fuse is to bond the freshly run ground to ths chassis and stack upon that. Problem solved.


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## birdie2000 (Jan 27, 2007)

durwood said:


> I guess all the other ground sensitive computer and other wires must need to be run all the way back to the battery too.


I'm not positive if most OEM computers do this or not (I think at least some do), but aftermarket ECMs are set up this way. My F.A.S.T. system in my Firebird has several ground and power wires in their harness that are specifically instructed to be ran directly to the battery posts, or power cutoff switch if equipped.

Also ignition boxes such as MSD are supposed to be wired directly to the battery on both positive and ground. I've heard from several people that the most common reason they see them failing is because of poor grounding.

I'm not taking a side in this debate, just throwing this info out there.


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## durwood (Mar 7, 2007)

chad said:


> In some instances the sheild is bonded to chassis, like my alpine for example, shield ids chassis ground. Which in turn goes to the AC that is using the grounded input. So it would melt the signal cable just fine along with the internals of both probably.
> 
> Really, the simplest way and CORRECT IMHO if you don't want to fuse the ground and as I said things will still melt due to the current rating of the fuse is to bond the freshly run ground to ths chassis and stack upon that. Problem solved.


I would think that gauge wire is so small though that it would melt well before frying anything else.



birdie2000 said:


> I'm not positive if most OEM computers do this or not (I think at least some do), but aftermarket ECMs are set up this way. My F.A.S.T. system in my Firebird has several ground and power wires in their harness that are specifically instructed to be ran directly to the battery posts, or power cutoff switch if equipped.
> 
> Also ignition boxes such as MSD are supposed to be wired directly to the battery on both positive and ground. I've heard from several people that the most common reason they see them failing is because of poor grounding.
> 
> I'm not taking a side in this debate, just throwing this info out there.


That is aftermarket though, they say that to be on the safe side. I'm talking about OEM ECU's. When is the last time you saw lots of ground wires coming off the actual battery post ground?


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## thehatedguy (May 4, 2007)

When was the last time you saw fuses or fusible links on grounds from the factory?


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## chad (Jun 30, 2005)

thehatedguy said:


> When was the last time you saw fuses or fusible links on grounds from the factory?


Most I have seen have 2 grounds from the battery. The thick one going to the block and a thin one going to the body. I watched the thin one become a fusable link once.


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## birdie2000 (Jan 27, 2007)

durwood said:


> That is aftermarket though, they say that to be on the safe side. I'm talking about OEM ECU's. When is the last time you saw lots of ground wires coming off the actual battery post ground?


I'm not positive, but I believe on my Firebird the OEM ECM had several wires that were grounded through wires and not the chassis. Kind of like a star pattern within the harness. I can check the schematics though, I could be wrong and will gladly admit it if I am.

Also that's partially true about the aftermarket I'm sure, but I know that it's also for consistency. Serious racers need dead on consistency to win races and keep the engine happy.


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## durwood (Mar 7, 2007)

thehatedguy said:


> When was the last time you saw fuses or fusible links on grounds from the factory?


never. I don't believe in any of this hog wash for 90-95% of the peopel out there.

If you are not an spl vehicle, but are above 1000W, then I see a need for the big 3 upgrade.

A new ground wire to the trunk is for people who have listened to someone who wants to sell more wire and believed them, or are in the process of destroying their hearing, or they just like to overdo everything.


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## Hi There (Mar 16, 2007)

On fusing ground wire: Given the size of the electrical load you'd wish to interrupt (accessories operating normally at 12 volts suddenly grounding themselves through the chassis of your amp because their other path is interrupted), you'd have to bring the fuse rating too close to the amp's rated power just to get it to blow for such a fault ...for example, what happens when there is a fault in your vehicle's OEM chassis ground when your amp isn't on, or isn't operating at a significant portion of full power when the fault occurs????? The ground wire fuse never blows, that's what, because it has to be of a size to carry all the current when the amp IS at full power, which is likely some significant portion, if not greater than, all the current generated from the rest of your accessories combined. Given a fault in the OEM ground wire, the fuse on your dedicated ground will end up only performing its intended function under certain, very specific conditions of amp loading, which have nothing to do with the risk the fault generates. Either you compromise your power output with a "too small" fuse, or you do very little to protect yourself with a "too big" fuse, or you get one in the middle, which pops at inopportune moments, and frequently. Do the math for a fuse on the dedicated ground wire of a 1000-watt amplifier, assuming a 450-600 watt electrical load from the rest of the operating accessories in the car...then assume the amp is off or at low power when your OEM ground wire fault occurs.


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## thehatedguy (May 4, 2007)

I thought the whole point of what we do to our cars was the very last thing you said- people who want to over do everything. We don't just stop at "OK" most of the time...why not go the extra step there too?


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## durwood (Mar 7, 2007)

birdie2000 said:


> I'm not positive, but I believe on my Firebird the OEM ECM had several wires that were grounded through wires and not the chassis. Kind of like a star pattern within the harness. I can check the schematics though, I could be wrong and will gladly admit it if I am.


That's possible, but you will still have a voltage drop if it's a connection point and not wired directly to it.



> Also that's partially true about the aftermarket I'm sure, but I know that it's also for consistency. Serious racers need dead on consistency to win races and keep the engine happy.


I'll agree, again this is another extreme case. Extreme cases have extreme remedies.


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## durwood (Mar 7, 2007)

thehatedguy said:


> I thought the whole point of what we do to our cars was the very last thing you said- people who want to over do everything. We don't just stop at "OK" most of the time...why not go the extra step there too?


Because I don't waste my money on things I can't put a value on or see or hear a drastic difference. Some people will and do. I however am not made of money. 

(I guess I better run a whole new 2 gauge wire to my battery for my two amps that barely accept 2x10 gauge wire)


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## chad (Jun 30, 2005)

Here are a couple posts from other forums regarding the installation of RF accessories directly to battery ground (it's important for RF stuff to go back to the battery)

#1
Some things to remember:
Make sure you remember to run both a hot and ground wire from the battery since not having a VERY low resistance ground wreaks havoc with some radios.
Remember to place either fuses or circuit breakers on both the hot and the ground as a fault could cause damage on either end.
Next, remember to ground all cases with a separate screw to the chassis of the vehicle. Power supply wires dont always provide a high quality ground for the case of the radio.
Remember to always locate mikes, accessories, and displays in locations that are easily reachable, in a way that they dont block your lines of vision, and also are safe in the case of an accident.
Finally, remember to properly seal any holes you drill through the roof or side body panels for antennas/cables/mountings so that you dont get rust prematurely.
Oh, also, if you're doing HF mobile, and have a large antenna, make sure to properly secure the base of the antenna as the moment at the base of the antenna at highway speeds can be significant.

If you've got any other questions/comments, post em.

#2
Interesting. Chrysler recommends against running the ground back to the battery. Their reason is because if the main ground lead from the battery fails then you will have all of the vehicle seeking ground thru the radio. Since most rigs now have a large main ground to the block and a smaller ground to the chassis, I have been using the same ground point as the smaller ground lead. As far as computer problems I have heard of that some F s didn't have the side of the computer that faced the fender shielded, just potting compound facing out. And that to use two way radio's you had to go in and improve the shielding to keep stray rf from radiating from the fender into the confuser. The two meter will get a roof mount antenna. Haven't decided on the 10 meter yet, going to go surfing and see how Uncle Sugar mounts the big antenna on their rigs, maybe find a surplus hf antenna system.

My Expierience......
It is proper practice in RF apps to fuse the ground when running to the battery. I installed RF gear in cop cars, we fused all the grounds at the battery. One guy did not, he does not work there any more. I took the station van in once to have some electrical work done on it (Alternator Rewind), we had an inverter to power the Marti and wireless. The electrtical shop guy (Sami) **** a brick when he found the inverter unfused at the battery. And explained this to me in great detail with some interesting angry Iranian flair.

It's not uncommon and regarded as a common safety practice. If you don't see it in you car audio circles it's not my problem but I'm fusing a groundline back to the trunk* if it's not bonded to the body back there*.


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## chad (Jun 30, 2005)

Hi There said:


> On fusing ground wire: Given the size of the electrical load you'd wish to interrupt (accessories operating normally at 12 volts suddenly grounding themselves through the chassis of your amp because their other path is interrupted), you'd have to bring the fuse rating too close to the amp's rated power just to get it to blow for such a fault ...for example, what happens when there is a fault in your vehicle's OEM chassis ground when your amp isn't on, or isn't operating at a significant portion of full power when the fault occurs????? The ground wire fuse never blows, that's what, because it has to be of a size to carry all the current when the amp IS at full power, which is likely some significant portion, if not greater than, all the current generated from the rest of your accessories combined. Given a fault in the OEM ground wire, the fuse on your dedicated ground will end up only performing its intended function under certain, very specific conditions of amp loading, which have nothing to do with the risk the fault generates. Either you compromise your power output with a "too small" fuse, or you do very little to protect yourself with a "too big" fuse, or you get one in the middle, which pops at inopportune moments, and frequently.


I could not agree more, it will still eff sh*t up. Which is why I'm STILL asking if people are bonding tot he body at the star of the termination... It seems only logical.


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## exmaxima1 (May 31, 2007)

chad said:


> Big difference, the ground in a car the SOURCE of the current flow, it is TO BE a current carrying medium.


And it's at zero potential. It's your reference for zero volts. You never want that opened up for any practical reason. I had a VW that lost its ground cable from the alternator---the voltage regulator started going haywire, the dash lights fried, everything was going crazy. I'd hate to think what could happen to the electronics in a modern audio system if you significantly raised its ground potential either through alternate ground paths (blown ground fuse), or by the simple added resistance of a fuse.

I understand that this is a DIY forum, and people are allowed their opinions, but fusing grounds just makes me nervous. And I would hate to be the poor sap trouble shooting an electrical problem that ran across a fused ground in a car----I'm sure he would quickly rip that out! ..

Matthew


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## durwood (Mar 7, 2007)

exmaxima1 said:


> And it's at zero potential. It's your reference for zero volts. You never want that opened up for any practical reason. I had a VW that lost its ground cable from the alternator---the voltage regulator started going haywire, the dash lights fried, everything was going crazy. I'd hate to think what could happen to the electronics in a modern audio system if you significantly raised its ground potential either through alternate ground paths (blown ground fuse), or by the simple added resistance of a fuse.
> 
> I understand that this is a DIY forum, and people are allowed their opinions, but fusing grounds just makes me nervous. And I would hate to be the poor sap trouble shooting an electrical problem that ran across a fused ground in a car----I'm sure he would quickly rip that out! ..
> 
> Matthew


Me too


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## chad (Jun 30, 2005)

exmaxima1 said:


> And it's at zero potential.


And it only carries current while the breaker is blowing.



exmaxima1 said:


> It's your reference for zero volts. You never want that opened up for any practical reason. I had a VW that lost its ground cable from the alternator---the voltage regulator started going haywire, the dash lights fried, everything was going crazy. I'd hate to think what could happen to the electronics in a modern audio system if you significantly raised its ground potential either through alternate ground paths (blown ground fuse), or by the simple added resistance of a fuse


Well....Uh...Yeah, lift the ground reference on ANY voltage regulator and see what happens Simple bench test... Grab a 7805, shove 10V at it and lift the ground reference. You get 10V, it ain't rocket science. Apply pos 2V to the leg in reference to ground and you get 7V out.... simple voltage regulation.

So your car amp..... You have 12V and ground, raise ground to 2V and you have 10V of potential. No biggie, nothing is gpoing to burn up, you will just have 10V to deal with. Now lets say your fancy ground wire comes undone.... and the amp has a grounded input stage, fuse or not you just tore up the output stage of the head unit or the input stage of the amp. 

So I'm going to waste some fingerprint by asking again..... Why not take the seperate ground you ran that is so low in resistance and decrease it's resistance further by bonding it to the chassis? Will someone please answer this? And Durwood's question while we are at it? What are the benifits? Has anyone actually measured this? What are the real numbers?



exmaxima1 said:


> I understand that this is a DIY forum, and people are allowed their opinions, but fusing grounds just makes me nervous. And I would hate to be the poor sap trouble shooting an electrical problem that ran across a fused ground in a car----I'm sure he would quickly rip that out! ..
> 
> Matthew


You will note that in another post I mentioned that someone lost their job for not fusing the ground, in other words not sticking to proven guidelines. If that poor sap decided to pull the ground fusing off of the RF deck in a goverment vehicle they would risk more than losing their job.


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## Hi There (Mar 16, 2007)

I think it would be smarter to take the ground wire of your amp to a grounding lug very nearby in the floor pan, and take the lug back to the battery with a cable...that way, would you have to worry about a fuse, since there would be an alternative, thick ass path to ground very nearby the chassis of the amp?

BTW, ground is at "zero potential" because we say it is. What represents zero may look like any voltage from other points of view.

Example: A man working at an electrical substation sees a 500 kv wire fall down and go to ground very near him. He's okay, though, because the wire didn't hit him, and he's careful not to touch the wire, and he's at the same 0-volt reference potential as the "ground" around him, no matter where or how he measures it...but when he picks up the substation phone to call in the downed line, he gets incinerated. The potential beneath his feet, although it looks like 0-volts to him, looks like 50 kilovolts to a person down the road. The phone line leads to another person's idea of "ground" potential, far outside the substation. By touching the phone, he creates the path from the "ground" beneath his feet, through his body and into the handset, thru the phone line, to another "ground" down the road (only that one is at a lower potential than his "ground").


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## chad (Jun 30, 2005)

Hi There said:


> I think it would be smarter to take the ground wire of your amp to a grounding lug very nearby in the floor pan, and take the lug back to the battery with a cable...that way, would you have to worry about a fuse, since there would be an alternative, thick ass path to ground very nearby the chassis of the amp?


Same here, That's the question I'm looking for an answer to. Seems absolutely ideal o me if you want to bump up the integrity of the grounding.

Chad


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## biggerrigger (Jan 14, 2007)

Back to my first post. Your entire power system is only as good as the ground back to the battery. If its clean and tight and of a larger gauge than the sum of all the small grounding points in the rig than your golden. If any thing is wrong with this single teminal point than you will have problems. If you dont belive me on this than go out and start your car turn your system up to painfull levels and remove the ground wire from the battery then let us know how many sensors and equipment you had to replace the next day due to not having a proper ground.
Aaron


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## chad (Jun 30, 2005)

No you lost the proper negtive connection to the battery, it's removed from the circuit, same thng would happen if you pulled the positive. the ground is still entirely there, the battery is a component of the electrical system.

That's like saying start yout car and dump all the oil to see what hapens with no wheels. the battery is not ground, the chassis is.


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## squeak9798 (Apr 20, 2005)

Was doing some other searching and came across this thread and thought I would contribute to it briefly. 

Manville stated on carsound previously that in his (albeit brief) testing they found that their test group's chassis' were equivalent to ~14' of 4awg wire;

http://www.audiogroupforum.com/csforum/showpost.php?p=339&postcount=66

So the poster on ICIX aswell as some in this thread may not be completely off base......


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## Suneet (Jun 19, 2007)

I just measured 20ft of 0/1 ga cable I bought from KnuKonceptz.. it had a resistance of 0.6 ohm. I'm going to use that cable to measure the resistance between the negative terminal on the battery, and the grounding spot I use in my trunk.

This is a 94LS400 BTW. I'll use the same 0/1 cable to measure the resistance from the trunk.


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## Diru (May 23, 2006)

Buhahahaha,

Don't forget to bring all your gear grounds to the same place[star ground{at the batt/ or at the gear-amp rack}].

Besides adding 14' of 4ga. isn't going to brake the f'en bank. [$1.00 to $2.50 / ft] Hell, I'll bet many have spent more then that on beer and few burgers in a weeks time.

Ok now lets look at this way. Battery to block ground 4 to 6 ga yes? sure about that. Now the battery to chassis ground what about 10 to 14 ga, about right. 

So here you are pulling your current from a chassis ground out of the floor of the trunk. how does it get to that point again, ohh yeah thats right , that 10 to 14 ga batt to chassis wire and also some from the poor tranfer points like the drive shaft into the suspension.

Hummm, more thought to be applied, ign , ecu , ecm , ac , fans , blows , pumps , and any other current drawing devices that make a car run pull thier grounds on the same 10 to 14 ga batt to chassis and block to battey ground.

To me that is a lot of potenial noise from the crap that make your ride go. 

Now why was it a problem to run that audio system ground to the battery again, ohh yeah its a waste of time and money.

In a RF mobile environment you got to have proper batt grounding. But, thats a hole new can of woop-ass. You should be thinking more like a RF type of install with your audio anyways.

Hence why the "F" bother running line and speaker and power wires as far apart as possible. It's cause you worry about the induced noise and , dare I say it "RF" noise. 


So blow me sandwitch. I will run batt+star grounding. 

Thank you , Thank you , I'm here every thursday at 8:00 pm{not really}


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## chad (Jun 30, 2005)

Diru said:


> In a RF mobile environment you got to have proper batt grounding. But, thats a hole new can of woop-ass. You should be thinking more like a RF type of install with your audio anyways.
> 
> Hence why the "F" bother running line and speaker and power wires as far apart as possible. It's cause you worry about the induced noise and , dare I say it "RF" noise.
> 
> ...


And in every goverment RF "grounding" scheme back to the battery, every properly done amatuer radio rig, guess what's ont he negative wire within a foot from the battery?..... other than a ferrite??

Back from the dead!


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## Hillbilly SQ (Jan 26, 2007)

measured at the amps i can't seem to get my voltage to drop at all hardly with a 4awg ground on a streetwires grounding block planted firmly to a clean section of metal at the back of the cab. in my silverado i couldn't even complete the connection at this spot. i think it's either a fluke or the 06 sierra is build differently than the 01 silverado.


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## MarkZ (Dec 5, 2005)

Suneet said:


> I just measured 20ft of 0/1 ga cable I bought from KnuKonceptz.. it had a resistance of 0.6 ohm.


That seems high to me.


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## chad (Jun 30, 2005)

You really need a millihom meter. Common DMM's are not accurate at that low of an impedance.


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