My car was parked, but running, this morning and it was just fine. i came out of the car to drop my son offf and come back to hear the dreaded alternator whine. this is very weird how it just popped up out of no where while the car was running. mind you, i've had my system exactly like this for 2 years.

it's not there when the car is off, it increases and decreases with engine acceleration/deceleration. i've checked my amp wiring and it SEEMS ok...but i don't think that would be it since i don't get the noise when the car is off.

what do you think it is? how can i fix it?

 

Check all your grounds - HU, amp, etc.

Unplug your RCA's from the amp. If it's still there then you know the problem is after the amp. If it's gone, it's before.

 

you mean after the head unit, right?

 

If the whine is still there after you unplug the RCA's from the amp, then the issue is after the amp, because whine comes out of the speakers, so it's either the amp (which can include the amp ground), speaker wiring, or speakers themselves

If it's not there after you unplug the RCA's from the amp, then it's an issue with your RCA's or your head unit.