Ground Loop (tried EVERYTHING!)

[Wyldehorses]

OK, I have a 99 ford mustang Gt vert. Im running a Kenwood Mp3 Cd player, an MTX Thunder 6340 4 Channell an Mtx thunder 5000 d-amp with a lighting audio power capicitor. i have diamond audio components throughout. I recently developed a ground loop. I replaced the 4 channell, bought brand new top of the line RCA's, new power chords, and a distribution block to sit atop the power capacitor. i cleaned up the ground (seat belt bolt in the rear) made sure the wires were at least 18 inches apart ( i have power goin down one side, RCAs down the other. After all this i still have the annoying ground loop, the only thing i can think of is that my head unit isnt grounded correctly, but i cant seem to get at the ground behind the dash. I had the shop that did the install check it out and they couldnt find it, so im going to a different shop to see what they can do, what else beside checkin the headunit ground should i have them do. I was told that it could be my wires under the hood, my spark plugs, or my alternator too, but i dont think this is the case and im not about to spend any more money than i have to. So what am i missing? Thanks in advance guys.

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[forbidden 10+ year member]

Have you tried grounding direct to the battery yet?

 

[Spenser]

Don't ground directly to the battery or you'll just get a lot more noises that you don't want in there.. try finding a new place on teh chassis to ground it to.

 

[maylar 10+ year member]

What makes you say you have a ground loop... you got alternator whine?

Did it suddenly appear, or did you change something that made it happen?

 

[mrfreshnklean 10+ year member]

is the deck grounded? My deck isntt grounded except to the antenna.. thats ghetto.

 

[Slody4Futbol 10+ year member]

make sure the gain isn't too high on the amp... this happened with a truck the other day... big escalade with 2 memphis amps and he had a whine in the speakers... checked his 4 channel... the gain was ALLLLL the way up for some reason... retuned it and it was fine...

 

[Wyldehorses]

I tried moving the ground... no luck. checked the amp out, even got a new one, no luck. the only thing i can think of is that it might be the head unit ground, but i can get behind my dash to check it. I just know that it started off not so bad, then progressively got worse. I took my car off the road in november, and just put it back on the road about 2 weeks ago, and replced the amp, the wires, and got a new distribution block to cover my capacitor. I tried gettin the wires as far apart as possible, but i dont get how it can work perfectly for over a year and a half set up one way, and then not. beside perhaps a bad ground from the Headunit that may have come loose, what else could be causing this problem?

 

[Mark_ab 5,000+ posts]

If you have alternator whine, you have a voltage differential in your grounding points. Break out your digital multimeter and reground again, including upgrading the HU ground.

 

[forbidden 10+ year member]

And like I mentioned earlier you may have to ground to the battery if the circumstances warrant it. Grounding of components is usually the source of many a noise.

FYI, grounding to a battery does not and will not put a whole pile more noises into the amp, sorry Spenser. The post above may be bang on, a difference in ground potentials, when there is a bad ground in one component, that component goes looking for another ground to complete the circuit, the next available ground path is through the shield of the rca cable.

Are your power/ ground and rca cables ran anywhere near an engine control computer or BCM module? These modules emit RFI that may be induced into a line and cause grief as well.

Reground the cd player to a different spot, make sure there is no other ground wire attached to the circuit. Leave the cd player out of the dash, do you have noise with it sitting on the seat? Is the amp mounted anywhere near another electrical component? Unmount the amplifier as if it is mounted the screws are more than likely also providing a ground path, place the amp on cardboard to eliminate that path, do not remount while trying this.

 

[Sharp_Shoota 10+ year member]

U can get haynes manuals at ya manufacturer or somewhere and that will tell ya how to get to the back of dash to find the ground for the HU.

As for ground I've found the best place is by sanding the paint of the shasis under the door skirt.

 

[homer3304 10+ year member]

Try grounding the HU to the same point you have everything else grouded at the seat bolt. I have also had a loop develop before through the antenna. You might check to see if is creating the problem ???

 

[Pete 10+ year member]

I agree with running a new ground for the headunit. Use 8 guage (a bit overboard, but that never bad) and run it back to the seat bolt and ground everything to the same point. Then if that doesn't fix it try the cardboard trick for the amp (remove all the screws and set the amp on a piece of wood or cardboard) see if the noise is still there.

If its still there try regrounding everything to a different point. If all that doesn't work try disconnecting the rca's from the amp itself and try revving the engine... it could be the amp itself generating the noise.

Let us know how all that turns out.