f 350 diesel severe interference

im reposting this in a more appropriate forumThe vehicle:2001 Ford F-350 Super Duty Diesel 7.2ltrThe System:Pioneer AVIC-f700BTRockford fosgate amps, 2ch and a 4ch and a .5f capThe problem:this problem started when i was installing an starter kill switch using the wires at the ignition harness. i installed the sound system a couple days ago and it has worked fine until today. i was testing the kill switch so i was cycling the ignition. i turned the truck off then to run and had a significant amount of interference that hadnt been there just a few moments ago.here's what ive done so far to narrow down the problem:regrounded the head unitchecked amp grounds. goodran rca directly to the amp, still buzzed.there is absolutely no interference in ACC, only in RUNi pulled the radio fuse and the buzzing still existedso i started pulling fuses until the buzzing sound went away and i found that the circuit causing the interference is 30amp fuse that controls the fuel heater, wastegate solenoid, and the injector driver module relay. This is all diesil only equipment.i pulled out the injector driver relay and that eliminated half of the interference but not all of it. i dont know what the wastegate is and the fuel heater im assuming isnt active because it's a warm day. also, when the 30 amp fuse is pulled the wait to start light doesn't come on. the sound doesn't seem to be following anything as far as i can see. when the truck is running turning on the AC or anything else that draws a lot of power changes the tone of the interference.so this is where i'm at now, i tried disconnecting the kill switch and checked all the wiring and its fine so i know its not the kill switch. i dont know what to do next... any help at all would be greatly appreciated, i think my client is scared i really messed something up so i want to get it fixed asap! Update: i've ruled out the rca's and the 4ch amp being the culprit. here's a couple videos of the sound im hearing. the truck is not running, the background noise you hear is the interference coming from the speakers, at the end of the second video i disconnect the radio and it goes silent but i dont think its the radio... what could be causing this?! Video 1 Video 2

Wow You checked a lot of stuff there. I sure wish I had an idea that would have saved you all of that time.

i am an idiot wrote: Wow You checked a lot of stuff there. I sure wish I had an idea that would have saved you all of that time.

so you still think it's the head unit? even though it worked just fine a day ago?

for some reason the word youtube isnt in those links, here, try these: video1 video2

Those video links dont work... try these video 1 Video 2

When you turn the volume from 0 to 1, or from 1 to 0, does it make a pop in the speakers?

no it dosent. i really appreciate the help by the way. one thing is.. the sound doesn't start until a few seconds after the ignition is turned to run. you can hear the long beep in the video and a few seconds later the buzzing starts. i'm wondering if the thing thats causing the interference doesn't turn on until the truck has been in run for a few seconds. i was thinking it might be the radio delay while it's loading but when i remove the radio fuse it still buzzes so i know its not just the radio itself causing the interference.

If you haven't already tried, use a different HU from a buddy and see if the problem presists. If it does, then it's a wiring issue. Have you tested your resistance to ground onthe HU and the amplifiers ? I know you stated that you ruled it out, but did you test it to rule it out ?Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

Hey and just for grins and giggles, while you already have the meter out, unplug all RCA cables from the back of the radio and check the resistance from the shield of the radio's RCA jacks to the chassis of the radio.