unwanted noise

[2000GTGP]

title says it all....

so heres the problem i recently had 4 channel amp put in. The first day i got it back i had alternator whine so i take it back they fixed it, no more alternator whine but i still have a pretty loud noise coming from the speakers. i believe it to be a problem with the lights on the car. If i turn the car to accessories and turn the headlights on i get this loud buzzing noise. If i turn it to parking lights the tone changes very little to higher pitched buzzing noise but still pretty loud. Now when i turn the lights off that noise is pretty quiet and at an acceptable level. Also when you sit in the car and lights dim and go off the speakers pick that up and play it as well. kinda makes a "zzzzzzzzzp" noise. so my question is how would i go about fixing this? would this be something in the dash cluster/wiring harness for the headlights/interior light?

[1LoudGrandPrix]

somethings off in the wiring and odds are you have 1 or more bad grounds..

currently my one of my amps have a bad ground and it makes the sound of a pissed off bee

[2000GTGP]

grounds should be good. i have 2 amps 1 for sub and 1 4 channel. I first had the sub amp installed about a year ago. it had a bad ground first go around so brought it back and they redid all the grounds for it and it was perfect. This amp is grounded to the same place so shouldn't be the problem? also when i first brought it back for alternator whine he checked all grounds to make sure they were good. only thing i can think of is the power cables and rca are ran through same side of car but ive heard that doesnt matter much anymore with the wiring they have available now-a-days. its picking up EMI from somewhere though and i just noticed the lights have a lot to do with it. should i start by moving rca's away from power cables?

[1LoudGrandPrix]

or see how close they are to your lights

[I800C0LLECT]

Grounded to the same place? Noise traveling through a vehicle is typically caused by a difference in grounding points or non-sufficient ground. Therefore, feedback is found all over the place to compensate for poor choice in ground.

#1) Increase the surface area of contact the current ground maintains. You can't increase the need without increasing the ability to transfer that need.

or

#2) Find a second location for a ground and hope a ground loop isn't created.