my amp does not turn on im guessing because of the ground...

is this a bad ground? , its behind the seat in the trunk under the carpet. 94 accord coupe

 

NVM, apparently...


Modified by White Smoke at 12:13 PM 9/3/2008

 

I sure as **** wouldn't be grounding my amp anywhere my fuel pump access cover...

Let's use a seatbelt bolt or some other suitable ground location that's not a fire hazard, mmmkay?

 

That is almost the worst job of grounding that I have ever seen.

Nevermind, I just remembered something. One time there was an amp grounded to the nut that holds in the tail light.

Look under the car for a spot where there's no fuel tank, fuel lines, brake lines etc. The frame rail is ideal. Get a wire brush attachment for a drill. Take the paint down to bare metal (this is inside the car now). Get three metal tapping screws, a star washer aka lock washer, and secure the ring terminal.

Never a bad idea to measure the resistance from your ground to the battery ground. You'll need some really long leads or you'll need to use some wire extensions.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18C_EJ8 &raquo;</TD></TR><TR><TD CLASS="quote">I sure as **** wouldn't be grounding my amp anywhere my fuel pump access cover...

Let's use a seatbelt bolt or some other suitable ground location that's not a fire hazard, mmmkay?

</TD></TR></TABLE>

No, do not use a seat belt bolt. Ask an MECP Advanced tech why not. Not me, I'm going to work.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by baller status &raquo;</TD></TR><TR><TD CLASS="quote">

No, do not use a seat belt bolt. Ask an MECP Advanced tech why not. Not me, I'm going to work.</TD></TR></TABLE>

Hmmm... I guess they didn't cover that in the Basic MECP manual when I was certified...

I really don't see a problem if you clean the grime & paint away from both mating surfaces.

I mean, seatbelt bolts are usually nothing more than nuts welded to the underside of the floorpan, which technically could be construed as a "bad" or "poor" ground, but hell, it's better than what he did in that pic... :shrugs:


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by baller status &raquo;</TD></TR><TR><TD CLASS="quote">Get three metal tapping screws, a star washer aka lock washer, and secure the ring terminal.</TD></TR></TABLE>

Why three? I always used two.. One through they ring and one through the shank (between the ring & insulated part). Never had one loosen up.

 

alright thnx for the info ima try a different place for it.

 

that's where my ground is for my 2 12's. i just scrapped some paint off so it was a metal to metal connection. and plus it is hidden under the carpet for a clean install

 

anywhere on chassis is a good ground, I'd say find a nice flat surface, get a wire brush and take it down to the metal, drill a small hole and use a machine screw with a star washer.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hueyduey &raquo;</TD></TR><TR><TD CLASS="quote">drill a small hole and use a machine screw with a star washer.
</TD></TR></TABLE>

LOL... A machine screw? How are you going to get to the back side to nut the screw?

A machine screw has nowhere near an aggressive enough thread to keep from coming loose....

 

I will agree with the rest, that is a very poor ground.

Ground to the floor pan of the car, any bolt or stud in the floor pan will work, seat and seat belt bolts work very well, as mentioned you need to clean paint and dirt down to metal, so the ground leads ring terminal is in contact with the bare metal of floor pan.

BTW I have been using seat and seat belt bolts and studs for grounds for more then 30 years, [yes that is before you could buy a car audio amp] and have yet to have found anything better.

I would never drill a hole in a car that is not needed, drilling a hole in the floor pan breaks the rust barrier, it is the first place your car will start rusting. 94

 

I used one of my rear shock bolts inside the trunk

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote">
BTW I have been using seat and seat belt bolts and studs for grounds for more then 30 years, [yes that is before you could buy a car audio amp] and have yet to have found anything better.</TD></TR></TABLE>

I respectfully disagree. As B18C_EJ8 admitted, the seat belt bolts; like many other existing bolts, are tack welded to the sheet metal of the vehicle. The strut towers again are separate pieces of sheet metal tack welded to the rest of the chassis. Tack welds are poor conductors, and while it may give you enough of a ground for the amp to function, it's also a very likely candidate to introduce noise via a ground loop particularly in 4 channel amps. 30 years or a million years of doing it improperly doesn't make it proper procedure. A new installer that has been working with me for one week will be doing it correctly or will be shown the door.

Everywhere I have worked as an installer it has been against SOP to ground it this way. I don't think that I would accept a job at a place that found this to be acceptable. And one of the first things I do when troubleshooting someone else's second-rate work is to re-do the ground because that solves the problem half the time.

 

I respectfully disagree.

You can disagree all you want, respectfully or otherwise, the debate about using seat and seat belt bolts and studs will rage on by the naysayers even when it is shown to them first hand that it works, as I have on many occasions, I will convince you also, if you will let me.

The first thing to remember is I am by no means depending on the nut that is welded to the bottom of the floor pan to be my ground, it is the contact of the grounds ring terminal to the sheet metal of the floor pan that insures a proper ground, what the nut under the sheet metal does is allow the ring terminal to be in contact to the sheet metal with 50lb or more torque, [you can't do that with sheet metal screws, no matter how many you use].

Because of this contact the connection point will not oxidise over time and build up resistance, unlike a terminal that is held in place with less torque then it takes to strip a sheet metal screw in sheet metal.

So try this, ground two 8ga cables, [12" long] in your car, or any test car, ground one using a seat belt or seat bolt or stud, ground the other any way you want, meter continuity of both to batt. neg.(-) terminal, both should be the same, if done properly my way, at least, will have full continuity, then meter them again each month for a year, then come back and tell me I have been doing it wrong for 30 years, and drilling a hole in a customers floor pan and pounding a few sheet metal screws into it is the correct and better way.

I will bet you my way will still meter full continuity after a year, [10 years for that matter] will your way.

You are correct about audio problems almost always being a grounding issue, and over the years I have found if it is a grounding problem, more likely then not it is because of a loose sheet metal screw or corrosion, [rusting] at the ground point.

BTW SOP in my shops have always been and will always be if you drill a hole in the floor pan of a customers car for a ground you will be fired on the spot 94

 

yea, that was a bad ground I changed it and placed it behind the seat on a 10mm bolt which actually worked better then before now my amps turn on.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote">
BTW SOP in my shops have always been and will always be if you drill a hole in the floor pan of a customers car for a ground you will be fired on the spot 94 </TD></TR></TABLE>

How do you mount your amps when doing them under a seat for instance?

A couple of metal tapping screws and star washers may not be the prettiest but it is the best. If you want a test, try this: put loctite, paint, or pour soda and let it dry out on that seat belt bolt and then tell me how good the ground is. May seem silly but many factory bolts have some kind of liquid applied to them at some point.

I've never seen any problems from a metal tapping screw used for grounding no matter how old and I no one I have asked has either. I brought it up with the shop manager who built cars for Alpine and worked for Sony and for him it was a no-brainer. "Don't believe anything on the internet."

 

OK, one more time, it is not the nut welded to the bottom of the floor pan, it is not the bolt that goes into the nut it is the contact of the ring terminal with the bare metal of the floor pan where the ground is made, the advantage of the nut and bolt is I can make that contact at 100lb of torque, not the 2lb-5lb that you can tighten a sheet metal screw in sheet metal to before it strips out.

You can spill whatever you want on one of my ground and it will make no diff. at all, my grounds do not oxidize as not even air will get in between the terminal and the floor pan at the contact point, your way, not only will air and moisture get between the terminal and floor pan from up top but because you punched a hole in the floor pan it will also get in from underneath, up through that tapered tread, you have also broken the rust barrier by exposing the inside of the sheet metal, [that you punched a hole in] to the environment.

I would fire your shop manager also, one of the first things I learned at Alpine install school, more then 20 years ago is never drill a hole in a customers car if you did not have to and never one that ends up outside.

Amps under seats, simple, first you glue down, [sub floor adhesive] a sheet of wood then mount the amp to the wood, sometimes it's just different length wood blocks at the amps mounting points, [3 will work] to compensate for the uneven mounting surface. [also glued down with sub floor adhesive, maybe a couple "L" brackets to the seats mounting cross member.
There are more then a few ways to do it without punching holes in the floor pan.

You can argue the point till your blue in the face and you will win the argument on one point only, it's easier and faster, and like anything that is done the easy fast way, it is never as good as doing it the right way.

Ask yourself this, why does Honda use machine screws into nuts welded to the other side of sheet metal for their dash harness grounds, or bolts through brackets with nuts welded to the bracket for bigger grounds, why is a nut and bolt used on a batt. cable clamps instead of just a screws.

BTW, I have also built more then a few Alpine demo cars, also Sony ES demo cars, Nakamichi demo car, Boston Acoustic and Soundstreem demo cars to name a few and not counting competition cars, take my word for it, not one of them used sheet metal screws for grounds. nuf said 94

 

I'm with FCM on this one. If I found that a shop had drilled my floor pan I'd be choked.

 

glad you got it working......


plus i belive the screw that covers the the fuel pump has a plastic retainer that holds the screw..so thats why it was a bad gnd.