Buzzing w/ dome light on "Auto"

[SuperBlack350z 10+ year member]

Hey all. I've got a problem with the system in my fiance's car. Whenever the dome light is set to "auto," there is a VERY loud buzzing coming from the front speakers. She's got components up front, fed by a Polk audio two channel. If you disconnect the RCA's and fade the audio to the rear speakers, fed off of the radio, there's no problem. We've swapped amps and RCA's, so the problem is somewhere up front. When I take the radio out (Pioneer DEH-P6800MP) and plug it back in, the buzzing isn't there until I open the door, activating the dome light, and then close it. As the dome light fades off, the buzzing fades out with the fading dome light. If I turn the dome light to "off" or "on" the buzzing stops, but if I switch it back to "auto" it buzzes. I've checked the connections and can't find any problems anywhere. Any help would be greatly appreciated.

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[rrmccabe 10+ year member]

As a test, try taking a wire and running it from ground to the shield/case where your RCAs connect to the back of the head unit

 

[NissanKicker 10+ year member]

Did someone connect a wire in your Fuse box to you CD player? Like if your memory remote was shot... They run a wire from the fuse box to the back of your cd player????

 

[GMCJimmyslt2000 10+ year member]

u pry connected ur illumination wire to the dome light. Disconntect that and see if it works.

 

[SuperBlack350z 10+ year member]

Apparently something popped in the radio . . . we swapped out radios and it works fine. Put the old one back in, same problem. Anybody familiar with how good Pioneer service centers are?