Engine Whine with HU Output but not with LOC output - New Pioneer HU

[lostdaytomorrow 10+ year member]

So this is the deal:

With the RCA's hooked up to the Pioneer 6000UB I have horrible engine whine that gets worse with the gain going up on the Kicker ZX850.2. The components are Pioneer 720PRS's ran passive.

I just got the HU today and installed it so was looking forward to getting rid of my weird noises that was coming from the RCA's from the LOC that was connected to my stock head unit. This is what happened.

I hook up the brand new HU. The RCA's work perfectly fine when plugged into the HU on the front channel. All of the sudden while listening to it with my car parked this HORRIBLE loud noise starts in the left channel and I mean LOUD AS **** and like turn the car off ASAP what the hell happened I have no idea? Thought a channel went out on my amp or my crossovers fried or something but nothing happened because when I turned the car back on it was just the engine whine and no more loud noise. The engine whine started after the loud noises.

So I hook back up my RCA's that are connected to the LOC and there's not one bit of noise and the noise floor is perfect and everything sounds nice. The only problem is I can't fade because the LOC is tapped into the rear speakers.

What the hell happened?

1. I've already tried connecting the RCA's to the rear channel to make sure the HU didn't get jacked up and it does the same exact whine with the rear channel as well on the HU.

2. The weird noises I used to have (when i hit the brakes my front channels would click) with the LOC RCA's are all gone now.

Please help me out here guys. I have no idea how it just all the sudden jacked up.

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[IDSkoT 5,000+ posts]

Probably a pico fuse that blew.

Take your HU out, and get a piece of wire, strip it quite a bit, then put one part up against the RCA's shield [Metal part outside of the RCA], then put another part of the bare metal up against your HU.

If it stops, it's your pico fuse and you have a ground loop. We have many FAQ's on that.

My suggestion is wrapping a wire on the outside of the RCA, with the metal exposed to the RCA, then solder it to the RCA, then run it to a metal screw on your HU.

 

[lostdaytomorrow 10+ year member]

I've read all the pico-fuse stuff and that makes no sense here. This happened while the music was playing and nothing was installed incorrectly like the RCA's while the car was on or anything like that? If it's the pico then I'm just returning it to Crutchfield for a different HU.