Common ground vehicles

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=30691
Printed Date: May 06, 2024 at 12:10 AM

Topic: Common ground vehicles

Posted By: Lokim
Subject: Common ground vehicles
Date Posted: April 19, 2004 at 4:27 PM

how do i install a radio? (w/o running all new wires.)

Replies:

Posted By: icu400
Date Posted: April 19, 2004 at 4:46 PM

installing a new stereo all you should have to do is pop out the old one, and pop in a new one, get a wiring harness and you should not have to run any wires at all...

Posted By: forbidden
Date Posted: April 19, 2004 at 4:47 PM

With a floating to common ground adaptor. Run the new wires, it would be best that way.

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Posted By: Lokim
Date Posted: April 19, 2004 at 5:12 PM

is there any way to do it without running new wires?

Posted By: flynntech
Date Posted: April 20, 2004 at 1:16 AM

There is a reason why common ground systems aren't so 'common' anymore....

Stop being lazy and run your wires!

Posted By: mr12volt
Date Posted: April 20, 2004 at 11:24 AM

If you dont run new wires you run a better than good chance of frying your radio. With the common ground the negative wire coming off of the speakers are grounded to the chassis. When you wire the new radio to the chassis you can, and more ofter will, short out the radio.

Posted By: kmn5
Date Posted: June 01, 2004 at 2:07 AM

Yeah I got the EXACT same problem on my Lexus SC300
ARGHHH!!!!

I pulled out the factory headunit and factory amp in the trunk. And find out that it's common ground! Doh!!!
The factory amp generated the pos/neg signals for all the speakers.
But from the HU to the Amp it's common ground negative posted_image

Posted By: kmn5
Date Posted: June 01, 2004 at 2:09 AM

my only options now are to run new negative wires from the HU to the rear harness, or get a 4 channel amp and use the RCA to the rear then output the pos/neg signals from the amp....

any suggestions or comments??
thanks
Ken

Posted By: DYohn
Date Posted: June 01, 2004 at 8:17 AM

kmn5]Y wrote:

ah I got the EXACT same problem on my Lexus SC300
ARGHHH!!!!

I pulled out the factory headunit and factory amp in the trunk. And find out that it's common ground! Doh!!!
The factory amp generated the pos/neg signals for all the speakers.
But from the HU to the Amp it's common ground negative

Actually (if you have the system I think you have) you are seeing line level signals going from your head to the amp, not "common ground." Common ground means the negative on the speaker side uses the car chassis, and that is not the case in a Lexus. The line level signal from the head to the factory amp shares ground, but this is normal in many line level systems. If you are using a powered head unit and want to run speaker level signals from the head, you must run new speaker wires as you currently have none at the factory head.

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Posted By: jimmeezgolfvr6
Date Posted: June 01, 2004 at 9:29 PM

listen to the good advice above. for the amount of time you've spent looking for another way to do it, you could have run new wires already.

Posted By: oldsbravo5
Date Posted: June 01, 2004 at 11:04 PM

Could someone please explain the properties of common ground?

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Posted By: DNK6987
Date Posted: June 02, 2004 at 1:05 PM

why does a common ground short out a new head unit?

Posted By: forbidden
Date Posted: June 02, 2004 at 3:49 PM

For the same reason that if you take a battery and touch both terminals to the chassis of the vehicle at the same time.

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Top Secret, I can tell you but then my wife will kill me.