Head Unit Grounding Issue

[ulrisa 26]

I recently installed a Pioneer AVH-3200BT in my new car. I've been having alternator whine issues, and I've been trying to figure it out. I thought it may be the pico fuse at first but the head unit still has connectivity between the chassis and rca shield. I tried a ground loop isolator and it made it worse. I ran a new ground direct from the head unit and the whine went away, but a static remained. At first it was bearable, but it's gotten louder for whatever reason.

At one point today when I was troubleshooting it today, I removed the ground wire and the head unit stayed on! Confused, I tried to figure out how it was grounding, and it turns out it is grounding through the RCA's. The second I removed the new ground line, the whine came back louder than ever. This is definitely where the issue is coming from, but how would the unit ground through the RCA's? Has anyone heard of this?

Thanks.

[An-i-no 86]

The ground path goes through the RCA's to the amp's ground.

Some amps will even try to ground through RCA's (by going through the H/U ground) if they are turned on without a ground hooked up and f up the head unit.