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Long ground back to battery

 

New member
Username: Kkmike

Post Number: 1
Registered: 02-2004
I had a new amp installed yesterday (JL 450/4) - my 2nd amp, and since the 1st amp (JL 500/1) was running off 8 gauge wire, they wanted to run 4 gauge. So now I have 2 runs of 4 gauge, 1 to each amp; but he also ran 2 runs of ground back to the battery. I have read numerous times that ground should be short and to the chassis. And it's a long run since this is a Suburban. He said JL recommends grounding these amps directly back to the battery and so that is what he did. Well now I have alternator whine that fluctuates with the speed of the engine; worse the higher the gains are set. The RCA's & speaker wire don't run along with the power wires, so I'm hopeing I can rule that out (they do cross where they all meet up at the amps, but that shouldn't be a problem?)
I don't want to go back and leave the car there again, it's a pain - I am skilfull enough to run a ground - there is a seat bolt right there. So I have 2 questions; Is the ground probably the problem? And if so, should I disconnect the long ground and replace it with the short, or just add the short and leave the long ones too?

Thanks,
Mike
 

Anonymous
 
did you get it installed at an audio shop???

if you did then i'd never go back there again!!!sounds like they have no idea what they are doing!!!

It is best to keep your ground as short as you can, under 3 ft is best!!!

Dont run it back to the battery, just sand off any paint or anything that may not allow for a good connection at that seatbelt bolt....just ground it there.....it'll me your best bet!!!

just use a short ground and disconnect the long one....cut it and use the length you need......

sounds like the shop just wanted you to GIVE them a little my cash!!!!!
 

New member
Username: Kkmike

Post Number: 2
Registered: 02-2004
Yes it was an audio shop - a JL authorized dealer. He didn't charge for the wire specifically - the total was $225, included the 4AWG wire, fuses, RCA's, speaker wire, a little staggered "tier" he custom made to mount the amps onto so they both fit under one of the rear seats - it does look nice. The place came recommended; there are 5 or 6 of that chain of shops in my area, so it wasn't one of those "hey bud, I got a deal for you today" kind of places.
They said bring it back tomorrow and they'll troubleshoot it, but changing the ground wasn't the first thing on his list of things to try. I'm gonna re ground it myself tonight and see.
 

Silver Member
Username: Its_bacon12

Post Number: 180
Registered: 12-2003
thats most likely your problem is ground either on one of your amps or on ur head unit
 

Silver Member
Username: Its_bacon12

Post Number: 181
Registered: 12-2003
well you see the reason this may be is because all wire has a certain amount of resistance and the lower the resistance, the better....with a long cable, the resistance adds up to alot of its 10 feet for say and that can restrict the amp to put out only as much power as the ground will let it, thats why a short ground of equal or maybe higher guage is always the best way to do it because it will allow the current to flow more easily than if there was more resistance

thats the whole reasoning behind short ground cables, preferably less than 3 feet
 

New member
Username: Tbone

Post Number: 8
Registered: 02-2004
Yes, running the ground all the way back to battery does not make sense, when you ground to the vehicle chassis, it is rounted back to the ground anyway. Have the shop install a short thick Ground wire to a secure site.
 

Gold Member
Username: Glasswolf

Post Number: 1407
Registered: 12-2003
that was jsut dumb, unless the car is one of the rare imports that uses a floating or positive ground.

If this is a normal car, tell them to ground the amplifiers within 24" of the amplifiers, to bare chassis metal.
Don't let them try to BS you into believing the battery terminal is a good ground point. If anything he should have only grounded the battery and alternator using the 4AWG.
 

New member
Username: Kkmike

Post Number: 3
Registered: 02-2004
I posted this question on a couple of boards, there is quite a debate.
http://groups.google.com/groups?dq=&hl=en&lr=&ie=UTF-8&threadm=loB%25b.10196%24y Z1.8195%40newsread2.news.pas.earthlink.net&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3 DUTF-8%26group%3Drec.audio.car

http://www.caraudio.com/vb/showthread.php?s=fbba6f35226a021b9e1b23489a7b488b&t=5 2306

 

Gold Member
Username: Glasswolf

Post Number: 1419
Registered: 12-2003
the ground should e as short as possible.
the longer the ground, the more chance of introducing noise.
the cable gauge is dependant on distance run, and current draw. if the ground is longer, the gauge may also neet to be larger, which again, gives more chance of noise.

-GlassWolf
E.E.
MECP Master Installer
13+ years experience
 

New member
Username: Kkmike

Post Number: 4
Registered: 02-2004
Here is the reply I received from JL Audio when I asked why the owner's manual reccommended a short ground to the chassis and the installer was referred otherwise;

Mike,

Thank you for your interest in JL Audio. In the owners manual, you are going to find a recommendation to have the ground as short as possible. This can be done with most vehicle and most audio amplifiers. You can run a ground wire back to the battery. This can be better then grounding to the chassis of a vehicle. As long as the ground wire is as large as the positive wire, there is no problem.

We have done some testing on all different vehicles. This test was to measure the resistance of frames and uni-body constructed vehicles. The best are the vehicles that have a true frame rail, like your Suburban. You want the ground wire from the amps to be mounted to the frame. You also want to upgrade the factory ground return wire. This runs from the negative side of the battery to the frame. Now the best results only equaled the same resistance as a 4awg wire. Uni-bodies are like an 8awg.

This installer made sure that the ground return of the amplifiers do have the least amount of resistance. This preventing any type of voltage choke.
There is no problem doing this. As long as it is done correct. In this case, I am assuming it was.




 

Bronze Member
Username: Tbone

Post Number: 16
Registered: 02-2004
Once again, if you chassis mount the ground, it will be routed back the negitive ground of the battery terminal by the Factory Ground Return Wire. There really is no need to run the cables all the way to the battery, the negitive electrical charge will end up there anyway by way of the Factory Ground Return Cable.
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