# MKIV Amp ground question



## KeltronZero (Jan 29, 2012)

Hi all, I've been searching around but haven't been able to find what I was looking for. I've been trying to ground my amp, but it just never seems to work. I'm pretty set on using the seat belt bolt, as I've read many Jetta owners do, but I still can't get my amp to power on. My wires are brand new and everything is hooked up fine, the amp worked in my friend's car, and the area has been removed of paint like crazy. I was wondering if anyone could post a picture of their grounded seat belt bolt or specific details (ie, the order that you should have everything.)

tl;dr I need a picture of an amp grounded to the seat belt bolt.

Thanks


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## kwalton (Sep 3, 2001)

You might want to check the main power feed and turn on leads first.


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## ChupaCabrah (Jan 30, 2012)

Volt meter double check your lead. Double check your ground connection. I used the seat belt bolt as a common ground and also created my own ground and haven't failed with it. 

Sent from my PC36100 using Tapatalk


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## NFrazier (Jul 22, 2006)

KeltronZero said:


> *everything is hooked up fine*


The infamous words of every customer that comes in and needs me to fix their ****.

Amplifiers require three connections to power on.

1. Constant 12v power directly from the battery (fused within 6-8" of the battery).

This wire is to be ran through the firewall, into the car. Don't be a dip**** and run it through your fender, etc. This should also be a thick gauge, quality wire (none of that Wal-Mart/eBay crap).

2. Solid chassis ground.

This should be attached to BARE, not painted, metal of the car. I do not like using seat bolts as they are typically rusted or corroded, are painted themselves. This should also be a thick gauge, quality wire (none of that Wal-Mart/eBay crap).

3. Remote turn on (accessory).

This should be interfaced with a switched 12v wire in the car (easiest is terminal 75X under the driver side dash). 

Other than that make sure that the fuses on the amp are still good and that the constant power wire's fuse is also still good.


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## jokers10 (Sep 11, 2011)

I used the seat belt bolt myself, but I sanded down the area until I saw bare metal.


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## dorkage (Jul 7, 2009)

The best place I found is under the CD changer next to the sunroof drain. All other places I've used (top of the truck, spare tire well, trunk floor) has always caused ground loops. Keep it clean as possible and avoid going through things with lots of welds. Welds will create a diode like effect and cause a ground loop.


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## BassNotes (Mar 16, 2005)

No, you won't get a ground loop in a car. You might have a lousy ground, but not a ground loop.

And chassis welds are fine for conduction unless they're in such bad shape that their structural integrity also is doubtful.


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## NFrazier (Jul 22, 2006)

BassNotes said:


> No, you won't get a ground loop in a car. You might have a lousy ground, but not a ground loop.
> 
> And chassis welds are fine for conduction unless they're in such bad shape that their structural integrity also is doubtful.


If that's the case, audio reproduction in your car should be the last of your worries. lol


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## dorkage (Jul 7, 2009)

BassNotes said:


> No, you won't get a ground loop in a car. You might have a lousy ground, but not a ground loop.
> 
> And chassis welds are fine for conduction unless they're in such bad shape that their structural integrity also is doubtful.


A bad ground can cause a ground loop, and I've got them all over the trunk of a MK4.
The definition of a grond loop is two spots that are suppose to be at the same potential, but aren't. Putting current through a lot of welds will cause a ground loop since there is a potential difference between the actually chassis ground and the ground of the equipment.


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## BassNotes (Mar 16, 2005)

NFrazier said:


> If that's the case, audio reproduction in your car should be the last of your worries. lol


Exactly.


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## BassNotes (Mar 16, 2005)

dorkage said:


> A bad ground can cause a ground loop, and I've got them all over the trunk of a MK4.
> The definition of a grond loop is two spots that are suppose to be at the same potential, but aren't. Putting current through a lot of welds will cause a ground loop since there is a potential difference between the actually chassis ground and the ground of the equipment.


A bad ground connection is a bad ground connection, not a ground loop. You get potential differences not because of attachment to different points on the chassis but from excessive series resistance and/or reactance between the gear (that you're not doing a good job of grounding) and the attachment point on the chassis. This is why you're generally better off grounding different components directly to the nearest possible point on the chassis. The chassis is actually a big, extremely-low-impedance ground plane.

There's nothing electrically wrong with chassis welds unless, as I mentioned, they're bad--i.e., poorly done, inadequate penetration, cracked, etc. If they're structurally sound then they would certainly be electrically sound also.


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