SOLVED: Alternator whine in RF channel only

[modernist]

Yup. I'm gonna try to make one tonight, see if anything changes.

[TimeMachinE30]

Hood grounding strap in serviceable condition?

You said its missing?

[modernist]

Switched L and R channels. Still whining on the right. Also, disconnected right tweeter. No change.

Help!

[modernist]

I'm pretty sure it's missing. The noise is not affected by volume or HU setting. Stays the same whether the antenna is connected or not.

Here's a recording of the noise, speaker by speaker.

https://www.dropbox.com/s/antkpchymszs9oj/Whine.m4a?dl=0

[TimeMachinE30]

Hood grounding strap in serviceable condition?

[nrubenstein]

I can tell you that I need to work on that in the red car. Zero noise everywhere but the RF tweeter.

[modernist]

I just rerouted the front negatives under the carpet, still getting noise, the vast majority of which is in the RF channel. Both rears are completely noise free. LF has barely any noise. I checked everything when I had the carpet out a few weeks ago, didn't see any worn insulation or anything.

The RF speaker wires do run close to the main battery cable, but they ran there before as well. Does anyone have experience shielding an audio cable? Would it help? Wrapping it in another length of wire and grounding that?

[modernist]

Attached is a wiring diagram of my setup. 1986 325E. Alpine UTE-42BT. Upgraded from non-premium sound to premium speakers, converted from common to floating ground. Sounds fabulous when the car is off; rich, clear, detailed. When the engine is running, I'm getting loud alternator whine from the RF and very faintly from the LF. Rears don't whine at all.

My only idea is that the front negative cables are too close to the ECU and ABS boxes. Since they were the only wires I had to run, I decided to route them through the dash rather than tearing up the carpet. The RF negative runs through the space between the ECU and the dash, LF above the steering column, just below the cluster. I understand that this could cause interference, but would it sound like alternator whine? It does go up and down with RPM. All other wiring is in the stock locations. Checked and double checked all of my grounds, made sure the speaker chassis were not touching anything, plugs weren't shorting to anything .. stumped.

Edit: rerouted front negatives under the carpet. No change.