Ground Q/A sticky

RedKatanaX9 wrote: So after compling my notes I decided that it had to be the EQ. All the connections to it and from seemed clean but then I thought the factory +12 V constant wires was just too thin to power both HU and EQ. So I ran a fused 12 Gauge power wire directly from the battery to the HU and EQ, and voila, noise was gone!!! So all along the EQ wasn't getting enough juice, and perhaps was straining for power and somehow picked up alternator whine. Also gone was a slight high pitch humming even when the enging was not running. Thanks for all your help.

It's not a matter of enough juice.  The factory power wire is probably picking up interference from adjacent wires, like something going to the ECM.

Sorry for the first miss post (didn't like the cut and paste from Word).  Let me try this again.

I have a noise problem I cannot eliminate in a new system I installed in my 2000 Accord.  The noise is there only with the engine running.  I would not describe the noise as a whine, it is at a lower frequency but it DOES vary some with the engine speed.  When I unplug the RCAs fom the amp the noise persists.  I tried re-grounding the HU from the factory harness to the firewall ground as well as linking this ground to the amp ground via the third wire on my RCAs with no luck.  I am assuming I am getting power noise through the amp or the HU, not sure what I should try next.

Components:  HU - Eclipse CD5444, Amp - MTX Thunder 5400 5-channel, Speakers - Focal 165A front, 690CA rear, RCAs - Phoenix Gold

Install:  RCA's run passenger side, speakers in stock locations with one speaker wire running forward down each side of the car.  Power is 4ga run down the driver's side, amp ground is in the trunk on sheet metal attached to firm structure.  (I tested this with very little resistence between the bare metal and the negative battery terminal)  HU is grounded to the firewall, power is through the stock harness.

Appreciate any advise, the system sounds great when the car is not running.

I am unavailable right now to look into your questions. I am more than a little inundated with activity here at the shop. Once I have a chance to breathe again, I'll see if I can get to you questions.

arrrgh! the infamous alternator whining noise. i've been bitten. so before i go pulling everything apart, i'd like to see what the pros have to say:

i've just installed a new everything and i'm biamplifying the tweeters of a 2-component system, so they use the HU's amp while the mids get their juice from a separate JL Audio amp. so coming out of the HU I go straight to the X-over and into the tweeter. only the driver side tweeter whines from what I can tell. so does this mean the X-Over is introducing noise or is the the GND of my HU jacked?

the front L and R X-Over do not have symmetrical install locations. the driver's side X-Over had to go under the carpet of the driver's seat. the passenger's went under the glove compartment. is there anyway i can protect the X-Over from noise? shield it or whatever.  power is nowhere near this area by the way.

so I just measured the resistance between the battery and the HU GND, here are my findings:

a) positive battery terminal disconnected, ignition off: 0.3ohms

why does the resistance go up when the terminal is connected, or the ignition is on? does this behaviour explain alternator whine? the whine can only be heard when the engine is running, and would consistently fluctuate with the RPMs regardless of the resistance measured (between 5-13ohms).

so do i have a GND loop? or is noise coming in at say my X-Over?