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Discussion Starter #1
Hello all. I have a 2016 Focus SE with the 4 inch screen and I am hoping to get some help with an audio issue. I apologize in advance for the long post but I want to put down as much information as I can. A few months ago I installed a Memphis Audio 16-PR 100.4 4 channel amp.

Since then I have had alternator whine and a buzzing noise that increases when I depress the brake pedal and also when I use the turn signals. At first I bolted the amp to the back of the left rear seat. Then I bolted the amp to a piece of MDF and then to the seat back. Then I moved the amp to the trunk.

I used a CARAV harness and then a European version behind the head unit to a 4 channel PAC LOC and ran RCA's to amp. I then replaced the PAC LOC with an active NVX XPLOC4. There is a module behind the head unit so I thought that might be causing the interference. So I put the NVX XPLOC4 in the trunk and ran Stinger 9 wire from the T-harness behind the head unit.

I removed the T-harness from behind the head unit and spliced directly into the factory harness speaker wires (I know I know) and used the 9 wire. I believe the speaker wire from the amp to the factory harness is 16 gauge which should be plenty since the amp is only 50 watts RMS/ 100 watts peak.

I ran a ground wire directly from the battery to the distribution block. Disconnected that ground wire and ran a 4 gauge ground wire from a spot I cleaned in the trunk area. I also removed the paint from the main battery grounding point. Ran a new 4 gauge power wire. I used new RCA cables. Stinger 9 wire and speaker wire are under the sill plates on the driver side. Power and ground on the passenger side.

After doing all that, the whining and buzzing has NOT gone away. At this point I don't know what else to try. I'm thinking it might be the amp but I used the same amp with the PAC LOC in a 2017 F150 I used to have and it worked great. No noise, whine or buzzing. Again, I apologize for the long post. I know there are audio gurus out there. Thank you in advance for any and all help.
 

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I get the same thing, only when the rear tails or turn signals are on. I've been chasing the issue for the past year.

Aftermarket everything; I noticed it after installing the aftermarket tesla-style headunit but I don't remember if the same thing happened when I had the stock 4" HU and aftermarket amp. I've respliced and redone all the wires, grounds, power, speakers, etc I found this from an older thread, but I haven't tried it yet. Maybe it is an issue with the factory grounds going into anything non-factory.

well, there is 3 grounds that Come from the factory side harness, however there are then 3 grounds that lead into 1 small wire for the dsr-1. You’ll see what I mean if you get one. It is best just to ground that wire to where ever you have your amp grounded, if not when you depress the brake it causes a horrible buzzing noise and when you use your turn signals as well. So that fixed the problem.
 

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Thanks. I don't have a dsr-1 but which wire is being referenced? Yesterday I grounded the amp directly to the battery and left the LOC and subwoofer grounded to the distro block. No change. What year is your car? What side did you run the signal wires and what side the power, ground and remote?
 

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Thanks. I don't have a dsr-1 but which wire is being referenced? Yesterday I grounded the amp directly to the battery and left the LOC and subwoofer grounded to the distro block. No change. What year is your car? What side did you run the signal wires and what side the power, ground and remote?
2015 SE. Initially, I had the power cable running down the passenger side door trims but now I have the power cable running through the center console to the amp in the trunk, and the ground to a bolt in the trunk as well. Remote power is to a fuse in the trunk.

I think it's pin 12 of the power cable that's the ground (black I believe.) I can't remember the wiring diagram.
 
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