Battery Voltage on Ground Port of Amp

[Phatboiondiet]

Hopefully I’m posting in the right spot been awhile since I’ve been here. I’m installing a system in my 2008 S550 Benz. I’m using a Lc2i Pro to planet audio bb2400.1 amp. I have a good ground and fused battery connection. I test my ground with a power probe it shows ground and I test my battery cable and also shows good 12+ volts. When I connect ground to amp, the ground reads as ground. When I connect the power(battery) cable to the amp the ground becomes a positive 7volts. I’ve tested my setup with another amp and same thing happened. So I put back my planet audio amp and it worked I was bumping but then the sub went boom boom and green light on amp was on but blue leds were not. I then supplied ground from the power probe to ground port with my ground wire on amp and everything worked and sub played again. I released ground with the power probe sub made sound and did a boom boom again and amp “ON” light was green and no blue leds again. I have no idea why battery voltage is showing on the amp ground side only when I connect the battery cable. But then I supply ground through power probe to my amp with the ground connected and it works like nothings wrong.

 

[Water Bear]

Thanks for the reply! I went ahead and did what Water Bear recommended just now and the amp powers on and ground is ground showing -63V and my power probe lights green! Amp is on and all leds!! Super happy but my question now is could I run my negative from the battery permanently?

Yes. Grounding on battery negative is debatably the best ground. Ideally the engine block, frame, chassis, and battery negative are all tied together. The idea with grounding on the chassis is that the current flow makes its way back to the battery negative by flowing through those different parts. In practice many vehicles have resistance along that path, especially between joints in th chassis or connections to the frame.

When the connection is bad enough car audio guys will sometimes run directly to battery negative. The way I deal with it is doing a big 3 type upgrade where you manually tie all the components together with big ol' ground wires. The engine block, chassis, battery negative, and alternator negative are all tied together in my Tahoe.

 

[Water Bear]

Oh, one more thing. If you're grounding on the battery negative in your trunk, be sure to put your amp power wire on the battery positive in your trunk too.

 

[Phatboiondiet]

Oh, one more thing. If you're grounding on the battery negative in your trunk, be sure to put your amp power wire on the battery positive in your trunk too.

Water Bear you are a freaking genius!!!!!! Lol I’ve spent hours yesterday changing amps, changing my fuse to another fuse, and redoing my wires and stayed with the same issue. I should’ve calmed down and thought to hook up the negative directly to the battery just to check if it works but I assumed my chassis ground was good since it was reading good on my power probe and showing -volts. So I removed my ground and rerouted it to a factory ground I found in the spare wheel well and all is good now!!! Man thank you so much.

 

[Phatboiondiet]

MY SYSTEM WORKS GREAT NOW. THANK YOU ALL FOR HELPING

 

[Water Bear]

MY SYSTEM WORKS GREAT NOW. THANK YOU ALL FOR HELPING

Love to hear it. Now go let it pound.

 

[metalheadjoe]

Could be that he was getting ground through the RCAs.

I don't think rca's are chassis-grounded, which is why it is recommended to ground them if you have a lot of noise. Is that incorrect?

 

[rangedzs]

Thanks for the reply! I went ahead and did what Water Bear recommended just now and the amp powers on and ground is ground showing -63V and my power probe lights green!

 

[1aespinoza]

I don't think rca's are chassis-grounded, which is why it is recommended to ground them if you have a lot of noise. Is that incorrect?

It depends on the brand. My JL has 500k Ohms, old Fosgate has 80k Ohms, and old Orion has 80 Ohms. These are the ones I had on hand for testing.