# Ground to factory bolts?



## nonamedude (Oct 22, 2010)

I am trying to find a ground in my trunk. I was looking at a particular factory bolt but its too big for the ring terminal. I was also reading that your shouldnt ground to factory bolts(not sure why) and that you should drill your own hole. The problem with this is that the floor of my trunk is covered in something... I think i read somewhere thats its fiberglass, i dont know. I can take a picture or two if necessary. I keep reading differing opinions. Some say to use the back seat bolt others say its a bad place. Some suggestions would be great. 

Its a 99 civic lx btw.


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## seekingSQnirvana (Dec 21, 2008)

search: "ground"


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## nonamedude (Oct 22, 2010)

Not trying to be rude but I have already done that. I even did it again after you posted just to make sure I didnt miss anything. The only thing I had missed was that I shouldnt use a zinc plated bolt. I already know that I should mount to the chassis, or in my case the uni body, and it needs to be free of paint. I usually try to post only after searching and not finding anything, or searching and getting confused by what I find. This time I am confused.

I have seen alot of people with my car on the honda and civic forums like to use the seat belt point or back seat bolt. The reason I asked what I did is that I have also read on car audio forums and possibly on here as well that you shouldnt use a factory bolt. My problem with that is that very large portions of my trunk are covered with some sort of fiberglass like material.

Basically, is there a reason I shouldnt use a factory bolt, free of paint and other gunk as well as attached to the unibody?

If not then I will just find a bolt that will fit and clean up any paint.


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## JimAckley (Mar 22, 2011)

I haven't had a problem with factory bolts at all. If this is one of the big ones holding down a seat, etc, you'll need to cut away the carpet that's in the way (if any), sand off the paint on the body so your ring is sitting on pure metal, and sand the bolt down to get any coating off of it.

In one of my cars, I didn't have a bolt handy so I drilled a hole, and put one in place, but sanded away the paint, cut the carpet, etc before permanently installing it.


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## 000zero (Mar 12, 2011)

My brother had his amp grounded to the factory bolt that holds in the seat in his S-10. He was getting an insane amount of alternator whine, we made our own ground and the whine went away completely. YMMV.


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## nick650 (Feb 7, 2011)

Factory bolts is a nono. Do your own. Floor of the car or trunk floor is best. Make sure its clean, sanded and prepped.


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## nonamedude (Oct 22, 2010)

OK so going to make my own ground point then. I guess it really is a YMMV type thing. Thanks for the input. And thanks for the link SQ. That was one that I had indeed missed. Now the only thing will be to find a good spot. Hopefully I can get everything all hooked up this weekend.


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## bobduch (Jul 22, 2005)

Factory bolts are usually of the zinc plated variety. Zinc plating is bad for grounding. I know. The bolt only "sqeezes" the ring terminal to the chassis.
Lycan gave the technical reason a few years back as to why the zinc plated bolt can cause problems. Do your own and make sure the bolt/screw is not zinc plated.


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## nonamedude (Oct 22, 2010)

Yea I had read that on here. How do you know if its zinc plated? I guess the best way is to make your own and be sure to use stainless steel haha.


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## Mike_Dee (Mar 26, 2011)

Here is the simple fact. A ground is a ground. Make sure the contact surface is clean, bare metal, and the mechanical fastener is sound. A bolt, or weld stud/nut will usually maintain a better mechanical fastening than a sheet metal screw.


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## Clarion_Freak (Feb 29, 2016)

*Re: Grounding amp to factory seat bolts?*

Hello, fellow car audio buffs! I just joined the group/forum after googling to find answers to my grounding issue. So far, I was so excited to find this forum I only wondered how I had missed it before now! 

So, my problem is the worst alternator whine I have ever experienced in my 40+ years of installing car audio and security in all my own vehicles plus all my friends' and family members' cars. The weird thing is, this same exact set-up was just removed from my last car (a 1999 Chevy Prizm) in August of last year before I sold the car. I installed the head unit in the newer car I got in August, a 2001 Honda Civic (BTW... got from original owner with 54,000 miles on it!). I had absolutely NO whine at all in the Prizm! But now it's the worst I have EVER experienced!

This is my current system and how it's all set up:
Kenwood KDC-355U head unit.
Clarion SRG1622R 6-1/2" speakers (4).
Pioneer TS-110 tweeters with 5Khz Bass Blockers.
Boston GT-40 4-channel amp under passenger seat.
Clarion EQS746 equalizer.

As exactly like I connected everything in the Prizm, I have the head unit AND equalizer connected to the factory radio black ground wire. The head unit I put in back in August sounded crystal clear with no whine before I recently installed the equalizer and amp. As with the Prizm (and most other cars in the past where I put amps under front seats) I grounded the amp to the front outer seat rail bolt. It appears to be black metal against black metal. 

Everything works perfectly and sounds awesome... UNTIL I START THE CAR! Then the alternator whine is out of this world! Every tap of the brakes clicks, everything I turn on makes it worst, and every tap of the gas pedal increases it. 

So YES, I've read a LOT of your posts here as well as other sites and forums, but I'm getting mixed messages/opinions on grounding with a seat bolt. One post made a LOT of sense when the OP stated there may be the chance of rubbery tar stuff under it to stop rust. Never really thought of that.

I replaced the ground wire with 8g wire and a nice secure connector, but still have major whine! Then I disconnected the deck and equalizer ground wires from the factory radio ground wire and regrounded to a solid metal bracket behind the dash. No change!

I'm running out of things to try! I can only listen to my stereo if the engine is NOT running, so that has to change! I'm thinking about trying a Ground Loop Isolator between the deck and equalizer. If that doesn't help, I'm going to try grounding the RCA cables from the EQ to the amp. 

My main question goes back to the seat bolt: is this a BAD spot to ground on a Honda Civic? It sure worked fine in the Chevy Prizm. Just wonder if Honda puts anything between the bolt and bracket and frame between them. Any advice is much appreciated. I need to jam while I drive, not just parked.

Thanks. 
A DIY Moble Audio forum newbie


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## dablooz (Sep 27, 2011)

I'm willing to bet that there's a nick in one of the RCAs or speaker wires. The first thing I would do is get another long pair of RCA cables and run them (across the car) from the EQ to the amp. Test. If the whine/noise is gone, you know it's the RCAs. Checking the speaker wires will be more of a hassle but sometimes you gotta do what you gotta do.


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## SkizeR (Apr 19, 2011)

bobduch said:


> Factory bolts are usually of the zinc plated variety. Zinc plating is bad for grounding. I know. The bolt only "sqeezes" the ring terminal to the chassis.
> Lycan gave the technical reason a few years back as to why the zinc plated bolt can cause problems. Do your own and make sure the bolt/screw is not zinc plated.


ive been trying to find the answer to the zinc plated bolt thing for a while now. anyone know why? i have experienced myself that they arent the best, but why?


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## SkizeR (Apr 19, 2011)

Clarion_Freak, ground your head unit and eq to the same grounding point as your amps


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## adrianp89 (Oct 14, 2007)

I think a big piece on info here is missing. Yes always ground to sanded down bare metal, but ALSO make sure it is to the CHASIS of the car and NOT a part of the car that has been welded on, or bolted to the chasis. I.E. spare tire wells typically bad, but under the rear seats, typically good.


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## rob feature (Nov 15, 2015)

SkizeR said:


> ive been trying to find the answer to the zinc plated bolt thing for a while now. anyone know why? i have experienced myself that they arent the best, but why?


Wondering why myself. The zinc probably has a higher electrical conductivity coefficient than the steel nut/bolt it's coating.


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## Alrojoca (Oct 5, 2012)

SkizeR said:


> ive been trying to find the answer to the zinc plated bolt thing for a while now. anyone know why? i have experienced myself that they arent the best, but why?



No need to bother trying to find out, I've used a zinc bolt before on factory threaded areas.

The bolt presses on the ring terminal, and the terminal on the car body, that is the important contact, what is used to press it, makes no difference, it could plastic or wood.

Zinc bolts are cheap, and tend to be more of a lighter flat metal bluish color, less shiny.


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## Onyx1136 (Mar 15, 2009)

The only way to know if your grounding to a good piece of metal is to test it. Get a DMM with a set of xtra long leads. Set your meter to measure resistance/ohms. Scrape the metal you want to ground the amp to down to bare metal. Touch one DMM lead to the bare ground spot, and the other lead to one of the grounding spots in the engine bay. Look for a reading of 0.4 ohms or less. The lower the number the better. 

As far as the problem with zinc bolts, not the slightest clue. It would seem to me that as long as the ground lug is making contact with bare metal, there shouldn't be a problem. Maybe it has something to do with the galvanic response from the 3 different metals?


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## SkizeR (Apr 19, 2011)

Onyx1136 said:


> The only way to know if your grounding to a good piece of metal is to test it. Get a DMM with a set of xtra long leads. Set your meter to measure resistance/ohms. Scrape the metal you want to ground the amp to down to bare metal. Touch one DMM lead to the bare ground spot, and the other lead to one of the grounding spots in the engine bay. Look for a reading of 0.4 ohms or less. The lower the number the better.
> 
> As far as the problem with zinc bolts, not the slightest clue. It would seem to me that as long as the ground lug is making contact with bare metal, there shouldn't be a problem. Maybe it has something to do with the galvanic response from the 3 different metals?


your going to need a very good (also read: expensive) DMM to be accurately measuring impedances that low. not a great way to test


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## XR250rdr (Mar 22, 2011)

The only issue I can see with using a zinc plated fastener is galvanic corrosion between the terminal and the fastener. I would stick using stainless fasteners.

There isn't inherently wrong with using a factory bolt or stud as long as there is good contact between the panel and the terminal. If there is an unused welded in stud or insert it would be a good spot to mount to as long as all the paint is removed.

I am using one of the factory 3rd row seat weld studs for a ground point with zero issues. In my case I don't have a 3rd row seat so the terminal is attached directly to the base of the stud. If the seat was there I would have done something different.


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## I800C0LLECT (Jan 26, 2009)

I followed Lycan's suggestion about avoiding seat or seat belt bolts because of the zinc and never have had issues. Look around under the carpet and you may find a factory ground nearby.

Lycan never said you couldn't use those points without success but he said there a much higher probability of a ground loop.


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## Sine Swept (Sep 3, 2010)

I bought a bunch of M6 bolts and nyloc nuts to fasten future grounds. For what it's worth making a new ground is less work than dealing with a seatbelt bolt. If it is a customer's car, it is probably good etiquette to NOT loosen seatbelt bolts if you can help it. Using one also usually requires drilling out the ring terminal so it will fit.


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## Onyx1136 (Mar 15, 2009)

SkizeR said:


> your going to need a very good (also read: expensive) DMM to be accurately measuring impedances that low. not a great way to test


Even a cheap Fluke 117 has resolution down to 0.1ohm, with an accuracy of 0.9%. I picked one up at a pawn shop that was essentially brand new in box for $70. Even at retail they're less than $200. That doesn't qualify as expensive to me, but I don't purchase cheap tools, so I might be a bad judge. I tend to forget that a lot of people out there have no problem with buying Harbor Freigt tools. 

We're only talking about measuring for ground. If we were measuring a circuit for a medical device that was going to keep someone alive on life support, I would agree that splitting hairs is necessary. For measuring a ground for an amplifier, I think we're sufficiently accurate to measure a 1-2ohm grounding point vs. a 0.4ohm ground. Even if each measurement of off by 0.1or 0.2 ohms, it's still enough to discern a ad ground from a potentially good ground. At the very least we can rule out the very high resistance panels that are prevalent in a lot of unibody vehicles. 

SkizeR, if you've got a better way of finding the best possible grounding point in a vehicle, I'm always open to learning something new.


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## Alrojoca (Oct 5, 2012)

Adding dielectric grease to the thread, sanded area, terminal and bolt should prevent any reaction, corrosion or rust between the metals.


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## SO20thCentury (Sep 18, 2014)

My 6th generation Civic seat rails are painted black so would not make a good ground. If that's the case with yours I'd run the amp ground wire under the carpet up front to where you have the HU/ EQ grounded. And using a bolt straight to the body there would be better also. If you come across a closer place for the amp ground where you can bolt that ring terminal right against the body with no paint on it that would work too.


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## Clarion_Freak (Feb 29, 2016)

SkizeR said:


> Clarion_Freak, ground your head unit and eq to the same grounding point as your amps


You serious? That wouldn't make much sense since I'd be forced to run 3-4 foot long ground wires to the bolt under the seat. Plus, you NEVER EVER want to ground more than one thing to the same bolt/screw. I can agree with NEARBY, but not same point. BUT, yesterday I tried grounding the bodies of the head unit and equalizer to a separate ground but no change.

UPDATE: I grounded ONE PAIR of RCA's (the deck's output pair) and INSTANTLY the whine went 98% away! Still audible, but barely! And if I just turn up the volume a bit, I can't hear it at all. SO, think I could get the whine gone even more if I ground MORE RCA's? Should I ground ALL of them?


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## Silvercoat (Dec 5, 2013)

Its a Honda Civic....

There should be a large flat piece of metal behind the rear seats that is a channel. It is the floor part between the trunk and the seats where they fold down Easy to either scrap/tap or due properly with a nutsert. This should be one of the easier cars to ground on.

Also do not be scared to use factory bolts if you use the right factory bolts.

The bolts that attach the seat belts bottoms are great if you prep them properly. They are threaded into the unibody of the car. With proper prep there is no reason any factory bolt threaded to the unibody would not be a good choice. A wire brush on the drill and some marine grease/rust stop paint are your friends.


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## SkizeR (Apr 19, 2011)

It makes a ton of sense if you understand how ground loops works

Sent from my SM-G920V using Tapatalk


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## SkizeR (Apr 19, 2011)

And your "not wanting to ground to the same bolt" is false/a myth. 

Sent from my SM-G920V using Tapatalk


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## Clarion_Freak (Feb 29, 2016)

SkizeR said:


> It makes a ton of sense if you understand how ground loops works
> 
> Sent from my SM-G920V using Tapatalk


I believe after 40 years of this stuff I know about ground loops. That's why this is the FIRST car I've ever had this problem with. I figured it was just an issue with Hondas since the exact same complete system was in my last car and everything connected the same way with NO whine at all.

And BOTH of the MECP Study Guide & the IASCA Competition Manual (on my shelf for 20 years) talk about not grounding everything together.

But I still appreciate everyone's advice or I wouldn't ask for it.


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## Clarion_Freak (Feb 29, 2016)

Silvercoat said:


> Its a Honda Civic....
> 
> There should be a large flat piece of metal behind the rear seats that is a channel. It is the floor part between the trunk and the seats where they fold down Easy to either scrap/tap or due properly with a nutsert. This should be one of the easier cars to ground on.
> 
> ...


THANKS, my friend! That is what I wanted/hoped to hear... someone specifically mention a Honda Civic. Gives me a clearer picture. 

I tried the front seat track bolt for grounding the amp. It's painted, so I ground off the paint with a wire wheel on a bench grinder. No change in whine. 

So, you think grounding directly TO the floor sheetmetal might be a better choice? I'll try that. 

Thanks much!


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## What? (Jun 5, 2008)

Battery or alternator could also be bad.


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## SO20thCentury (Sep 18, 2014)

The civic seat rail is painted on both sides and the mounting point on the body's painted too. If you have the center console out I've grounded to one of the bolts retaining it's mounting bracket. I probably cleaned all paint off there too. And be certain your HU /EQ is a good clean ground. The fewer layers between the ring terminal & the body the better.


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## rob feature (Nov 15, 2015)

SkizeR said:


> And your "not wanting to ground to the same bolt" is false/a myth.


This is always how I've understood it and have used 'star grounds' before - bringing all the grounds together in a star pattern on a single bolt & successfully eliminated noise that way.


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## Clarion_Freak (Feb 29, 2016)

SO20thCentury said:


> The civic seat rail is painted on both sides and the mounting point on the body's painted too. If you have the center console out I've grounded to one of the bolts retaining it's mounting bracket. I probably cleaned all paint off there too. And be certain your HU /EQ is a good clean ground. The fewer layers between the ring terminal & the body the better.


Cool, thanks! Yesterday I did remove the amp ground from the seat rail bolt, and moved it to the steel dash brace suggested by a Honda owner friend of mine who has totally dismantled a few and rebuilt custom cars. He said the steel bracket is welded directly to the A-pillars on both sides of the car and makes a perfect ground.

NO LUCK! Still have the whine! I pretty much give up for now!


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## adrianp89 (Oct 14, 2007)

As someone mentioned, have your battery and alternator checked. I have seen this be an issue before.


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## Clarion_Freak (Feb 29, 2016)

the727kid said:


> As someone mentioned, have your battery and alternator checked. I have seen this be an issue before.


Thanks. I'll do that. Running out of things to check, so that's probably next. 

But the whine is present with just the key turned to the ON position. Yeah, first from the fuel pump for a few seconds. Then a very low buzz, and clicks when I tap the brake or turn on lights. I was trying this to see if it was there without the engine running. It's so low it's hardly annoying, the still there. It's when I start the car that all hell breaks lose!


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## Sine Swept (Sep 3, 2010)

When I check for noise I like to try 3 ways: Accessory on, key on - engine off, key on - engine on. In the very worst of circumstances you will get noise on the second test. In this case you would be picking up noise from the ignition circuit. Don't use the factory ground in the radio harness plug, make a new one.

If you are planning on running multiple amps, run a ground wire from your battery to your amps in the rear to a distroblock. When doing this though, don't actually ground it to your battery, ground it to the body ground that is connected to your battery. This way if your factory negative comes undone, your car doesn't get grounded through all of your amplifiers! When you undo the battery ground terminal, your battery will not be a circuit any longer. I found this the hard way once while using a top/side post battery running the ground straight to the side post. I took the top post off the negative and watched my protection lights on my amp flash on!


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## Clarion_Freak (Feb 29, 2016)

Sine Swept said:


> When I check for noise I like to try 3 ways: Accessory on, key on - engine off, key on - engine on. In the very worst of circumstances you will get noise on the second test. In this case you would be picking up noise from the ignition circuit. Don't use the factory ground in the radio harness plug, make a new one.


My noise is non-existent with the key OFF. Then, just turning it to the ON or ACC positions, the noise begins. Very little, but still enough to hear. And every time I hit something (brake pedal, lights, wipers, etc) I hear clicks. When I first turn key to ON, of course I pick up whine from the fuel pump, which goes away after a few seconds. 

LATEST UPDATE: Yesterday, at the advice from someone in another forum, I turned both my front and rear amp gains all the way down. WHINE WAS GONE! Then, as I started to turn them up (either channel, front or rear), I began to hear the whine. SO, now I'm wondering what this indicates. People keep suggesting I perform this test, but don't seem to want to tell me what it means.

I never ground my head unit to the factory harness. Nor the equalizer. The are both grounded to the main steel dash brace that is welded to both sides of the car. 

Also, I've moved the amp ground 3 times and even tried bigger cable, but no change in whine.


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## zapcoaudio (Sep 26, 2015)

strut tower bolt works fine for me.


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## Silvercoat (Dec 5, 2013)

Noise generally comes from a few common sources.

Bad Head unit Ground: Check resistance between the ground wire in the harness and various locations and a spot with sheet metal on the car. Honda subdash metals can rust.

Poor Quality Headunit: I have seen many a cheap and off brand headunits just have poor noise rejections capabilities. And let us not forget the infamous Pioneer Pico fuse.....

Bad Amp Ground: Anything that directly attaches to the unibody is a safe bet. There should plenty of metal/grounding bolts to do this. Remember to properly prep the metal.

Bad RCAs: This can come from either running them improperly (too close to power wire or not crossing at 90deg) Or it can come from loose connections. Try running a spare set just to test. The Headunit could also have bad RCA outputs which you can test by grounding the outer shield conductor.

Amp Gains too High: Most systems will have some form of noise floor. Setting gains too high will often cause distortion and introduce more noise or amplify existing noise. 

Bad Amps: It can happen just like a headunit. You would need to test this outside of the car.

Bad Alternator/Amp: If the rectifier bridge on the alternator is going bad or the battery is getting old then A/C can find its way into the DC system. You can easily test this with a digital multi meter set to A/C. There should be little if any in there.

Remember the mantra for troubleshooting:

Identify, Isolate, Eliminate.


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## Clarion_Freak (Feb 29, 2016)

I highly doubt my nice Kenwood head unit OR my Boston amp are bad. Nothing but trouble free since day one. I'm now starting to think it's just an alternator or battery issue. I've grounded everything about as good as I can ground it, so now going to stop moving grounds all over the car. My next step is to hook up an RFI Capacitor to the alternator. This should solve the problem.


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