Hoping you all can provide some suggestions.

Setup:
DEH-7200 up front
EQL underneath drivers seat
RF 500X on seat-back powering mids and highs
PPI 2160 powering IDQ10 also on seat-back. Seats have no path to
ground.

The engine whine in my car is killing me. I just spend 4 hours last
night moving grounds around, and finally routed the HU and EQ ground
back to the ground block in the trunk using 10awg. I know the ground
block in the trunk is good. It's been sanded down, and IS the chassis
of the car.

The whine isn't noticeable normally, but when the AC is on man is it
annoying. But after all the work last night, and now ground ALL my
equipment to one point I've still got it. Everything else is by the
book (RCA's and power on opposite sides).

The whine does not vary with volume. It does vary with RPM obviously.
The whine kicks in whenever AC is on, and you can tell when the AC
clutch engages and disengages with the whine noise. It is only
audible via all mids and highs, but this is probably due to the x-over
on the PPI amp.

Could it be due to poor ground from the AC unit to the body of the
car? Or from the car body to the battery terminal? The car is a 1997
integra. Any help is appreciated. Would a 10awg ground direct to
battery help? Anthing to get rid of this whine!

TIA,

Gordon