Re: Speakers make loud screeching/whining noise, only when car is running?
Sounds like bad grounding. I Dont know what kind of frame your vehicle has but if it had a chassis ground there. Disconnect rcas from amplifiers and see if the noise still persists. If it does you have bad grounding. If noise goes away when you disconnect RCA's, track back RCA's and run them about 12" away the positive runs that power your amps.
**Build in progress**
Electrical: Mechman 270 alt, Sky High Audio 1/0 CCA, Optima under the hood, interstate group 31 in the rear
Amps: SQ 3500D and taramps tl-900
Subs: 2 SQ HDC3.0 15's in 10³ at 31hz
Speakers: 2 sets of QC-HF6.5
Vehicle:White 1997 Ford F-150 Extended Cab