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Ground Q/A sticky


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djmoose 
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Member spacespace
Joined: August 26, 2004
Location: United States
Posted: September 23, 2004 at 10:22 PM / IP Logged  

forbidden wrote:
Do you have a meter? A single ground point for your amps is going to be a good thing. Using a factory bolt hole might not be such a hot idea though. Don't worry about your ground wire being too long, it is more important that it is the right guage for the length as compared to keeping it short.

Yup, both points have been measued.... .2 and .3 Paint has been scrapped off around the holes as well. Power to the amps is via 8 ga...and so is the grounds.

Just to make sure, what's the best way to measure ground resistance? I measured it back to the neg post on the battery...using 8 ga power wire as a "long lead" persay. Then connected the ground lead to the 8 ga wire, and then the pos lead to the point on the chasis. (where the amps are grounded now) and got .2 and .3 ohm respectively. Was this the correct way to measure? Do we also have to take in consideration the resistance of the long power wire I used back to the battery? (to the neg post)

forbidden 
Platinum - Posts: 5,352
Platinum spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
Joined: November 01, 2003
Location: Alberta, Canada
Posted: September 27, 2004 at 1:03 PM / IP Logged  

Did you make sure that the ground wire was disconnected from the amplifier? I would usually disconnect it from the amp and meter how you did. Yes you should also meter the length of extension cable used and subtract it from what the measurement is.

Top Secret, I can tell you but then my wife will kill me.
Ravendarat 
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Platinum spacespace
Joined: February 23, 2004
Location: Canada
Posted: September 28, 2004 at 7:30 PM / IP Logged  

Just along the same lines as this whole grounding thing, the one tech today did a brand new Chev DIesel and the factory ground was showing a resistance of 66 ohms. How nice is that. Nothing like making our job easier.

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer
djmoose 
Member - Posts: 18
Member spacespace
Joined: August 26, 2004
Location: United States
Posted: September 30, 2004 at 11:48 PM / IP Logged  

Just an update...the source for all the noise was the old school coustic xm-3 crossover. Just on a hunch, I enabled the high pass filter on the front RCAs on my HU...and hooked them directly up the amp for the highs...

crystal clear....no noise WHATSOEVER....alternator whine...GONE...hum....GONE...

Whew!! 

dirtydreams4x4 
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Member spacespace
Joined: September 24, 2004
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Posted: October 07, 2004 at 2:25 AM / IP Logged  
Rob,  You said that grounding to a factory bolt hole isn't such a great idea, why is that? Where is the ideal place to ground amp(s)?
forbidden 
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Posted: October 07, 2004 at 12:12 PM / IP Logged  
Most factory bolt holes are desinged to hold something in place, not to provide an efficient current transfer. In most cases the nut that the bolt threads into is tack welded into place, thus it is a very poor path for current to flow through. The ground is the most important line there is, if you are causing the electrical system to work harder by running the ground through bad points with a higher resistance on the chassis, the entire system will suffer.
Top Secret, I can tell you but then my wife will kill me.
dirtydreams4x4 
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Member spacespace
Joined: September 24, 2004
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Posted: October 07, 2004 at 2:53 PM / IP Logged  

Thanks Rob, that makes sense. I have my amp grounded to a bolt hole under my rear seat(not a seat bolt, smaller bolt (1 of 10) holding a bracket to the body, and everything seems to be working fine. I sanded all the paint off of the metal that the ring terminal touches, is this setup ok? I'm going to be adding another amp and I plan to ground them both to this same point,  but not if it could cause problems.

Thanks for the info!

Poormanq45 
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Joined: October 27, 2004
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Posted: October 28, 2004 at 5:52 PM / IP Logged  
Ok guys. I've read enough of this grounding crap. Taking a wire from whatever you want to ground and attaching it to the frame(Bare metal) is not a real ground.
To completely ground your system, you should hook up a ground wire from the part and connect it to the negative terminal on the battery. This will give you a complete/Proper ground.
It is a common mis-conception that the ground and negative wires are different. This is not true. They are one and the same.
BTW, I am an electrician. The ground and negative on a 110~130V house lead to the same place. It is just because of the Electrical Code that these two wires are kept separate until they reach the breaker/fuse box.
customsuburb 
Gold - Posts: 1,813
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Joined: January 17, 2004
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Posted: October 29, 2004 at 10:23 PM / IP Logged  

Poormanq45 wrote:
Ok guys. I've read enough of this grounding crap. Taking a wire from whatever you want to ground and attaching it to the frame(Bare metal) is not a real ground.
To completely ground your system, you should hook up a ground wire from the part and connect it to the negative terminal on the battery. This will give you a complete/Proper ground.
It is a common mis-conception that the ground and negative wires are different. This is not true. They are one and the same.
BTW, I am an electrician. The ground and negative on a 110~130V house lead to the same place. It is just because of the Electrical Code that these two wires are kept separate until they reach the breaker/fuse box.

The frame is connected to the negative terminal on the battery and therefore if you ground something to the frame it will be grounded (if it wasn't a ground then the amp would not turn on, or if the resistance between battery and alternator ground and the frame is to high then the amp wouldn't turn on either). Now the frame is not always the ideal ground like said above. If you are installing an amp in any GM vehicle you should probobly run a ground wire directly to the battery (or at least use a DMM to see what the resistance is to make sure that it isn't above 5 or 6 ohms).

Poormanq45 
Silver - Posts: 597
Silver spacespace
Joined: October 27, 2004
Location: United States
Posted: October 30, 2004 at 5:18 PM / IP Logged  
I just don't think the frame of a vehicle conducts electricity well enough.
I ran 2 6 guage wires to the back of my car, one on each side. Whereever I need to ground something, I run a short span of wire from the part to be grounded to the closest 4 guage ground wire. This insures a complete ground.
Also, with my method, you don't have to worry about your conection to the frame corroding.
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