Odd problems

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stevdart

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Posted: July 26, 2004 at 7:37 PM / IP Logged

And unrelated to above but an issue since you gave your information in the post: you have the power wire running underneath the car. That is not good. You should re-route it through the interior and into the trunk, and through the firewall...not the door... to the engine bay.

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Francious70

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Posted: July 26, 2004 at 9:36 PM / IP Logged

Rob, you mentioned checking the resistance of the ground, how exactly would I do that?? And it was also suggested that I move the factory ground for the battery, could anyone make a suggestion as to where I would re-locate it to??

And I'm not a professional installer, just work for myself and select friends, but thank you for the complement.

Paul

customsuburb

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Posted: July 26, 2004 at 9:53 PM / IP Logged

To check the ground resistance put one probe of the dmm on the metal of the vehicle where it was suggested to ground, then connect some speaker wire or similar gauge wire to the other probe and connect it to the negative post on the battery. Then set your DMM to the resistance setting and read awayyyy (I've heard you will get a mid 20s reading in ohms on most gm vehicles).

Ravendarat

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Posted: July 27, 2004 at 12:36 PM / IP Logged

I do check the resistance on grounds in the vehicles I work on and it is damn hard to find a goond ground in a gm but I cant think of a time yet where I didnt find and acceptable one. My main problem with running the ground all the way back to the battery is the inherited resistance that is going to build up in the wire over a run of that lenghth. Thats why I never do it.

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

Francious70

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Posted: July 27, 2004 at 1:47 PM / IP Logged

Ravendarat, on most GM's where is it that you find a good ground at usually? Is it always different car to car, or is one spot on a particular model always good?

Paul

kgerry

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Posted: July 27, 2004 at 4:25 PM / IP Logged

there is nothing wrong with running a dedicated ground to an amp, just like a dedicated power cable...in many cases of vicious engine noise it's essential....

and there really is no rule of thumb regarding the length of a ground cable...many manufacturers make the ground wire 3 ft long as thats the furthest it usually needs to be run...there is however a rule of thumb regarding the recommended impedence needed as a ground potential..... this is roughly less than 1 ohm resistence to true ground, ( battery ground ) regardless of the length of ground cable.... I always try to get less than 1/2 ohm to ground

this should not pose a problem, as if you grab a meter and meter a 4 ga. cable from the negative ternimal of the battery 18 feet to the trunk of a car, you'll usually only have .2-.4 ohms resistence down the length of cable....

Kevin Gerry

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Ravendarat

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Posted: July 29, 2004 at 12:10 AM / IP Logged

Good grounds are almost never in the same place from model to model. I have to admit that I have never actually checked the resistance of the ground cable that long, I was always just told it was insufficent. I guess Ill have to try that next time. Does that also mean when adding a second battery you should just reground it to the same point as the battery in the engine bay?

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

DYohn

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Posted: July 29, 2004 at 10:43 AM / IP Logged

ATTENTION BEGINNERS READING THIS: In general, a short ground cable (18 inches or less is optimal) connected directly to the chassis as close to the amp as practical is preferred.

But as Rob stated in many GM vehicles this is not the best choice. Running a ground back to the battery is also often necessary for Saturn and sometimes for Mercedes and SAAB vehicles in my experience. I suggest a max ground resistance reading of 1 ohm from the chosen ground point to the battery negative terminal or run a new cable to the battery (or to the engine grounding point.) I also suggest you over-rate the cable. I over-rate both the power and ground in all installations by at least one gage size from what is required for the total estimated current, which will help limit the unavoidable heat-related cable resistance.

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forbidden

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Posted: July 29, 2004 at 12:55 PM / IP Logged

Dyohn, if I have time or one of the others do, we should create a sticky for this. This topic comes up way to often.

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Francious70

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Posted: July 29, 2004 at 2:06 PM / IP Logged

DYohn, so would it be over kill to leave my ground attached to the chassis, but also running it back to the battery? The current is going to take the path of least resistance, so I figure the current will go either thru the chassis or direct, whichever has the least resistance at the time.

Another question, by running a direct line to the battery, would this kill the noise that I'm picking up somewhere down the line?

Thanks,

Paul

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