Grounding issues

[Brad!]

Here is hoping i can get some advice and or help :)

I recently upgraded some of my components only to find massive amounts of engine noise, and not your normal hiss, i mean cracking.

To set the story my system used to consist of the following

Head Unit: Pioneer F900BT

Front: JBL GT5 Components (6 1/2)

Rear: JBL GTO Components (5 1/4)

Amp: Sony 4 Ch (Some 400w rubbish)

Sub: Sony 1000w Sub

Sub Amp: Schnider mono block

This was all well and good, used to crank hard, with a bit of his here and there, but my ears had gotten used to it.

This set up was OK but i wanted more so decided to get a new 4CH AMP and a new Sub.

Sub went in with ease as you would imagine however the AMP not so well.

The first AMP i tried was a JBL GTO1004 which seemed plenty for the speakers i was running. When it was plugged in a had VERY bad crackling and even back firing for some stage.

I re ran speaker cables and RCA cables thinking it was noise and this didnt fix it. Took it to Strathfield where i bought the stuff the day before for them to have a look at it.

The first thing they said was cables. Obviously this had been ruled out but they tried it as well.

The second thing they said was the head unit. Now having a headunit that is close to $2k RRP i was shocked that it could in fact be this causing it; Add to this that all i had done is unplug the old amp and connect the new one. Anyway they still felt this could be the problem.

I asked if we could connect a brand new amp to rule out the AMP being the issue; Guess what, new AMP = no back fire.

After a bit of convincing they decided that they would exchange the AMP as being DOA. They supplied me with a new MTX Thunder 3400 which i asked to be installed and tuned.

1.5hrs later they gave me a call saying the car was ready, start the car and what do you know - there is engine noise.

Installer said it wasn't there before and yanked the RCA cables out saying these are the issue. After a heap of research i have found that Pioneer head units dont like the RCA to be hot swapped and can sometimes blow the PICO fuse inside the headunit. Guess what happens when the fuse blows - NOISE!

Anyway i get home and decide that i need to get rid of the noise once and for all. I decided to ghetto rig the RCA cables and ground them on the back of the head unit. To do this i got 16ga wire and wrapped it around the female RCA connectors and grounded them. After this was done noise was at maybe 1%, it was not be able to heard unless you were looking for the noise. You can understand my happiness after wasting a good 10hrs of time + Money + headache to find that the problem was fixed - NO ITS NOT!

Everything was fine no engine noise. Secured the head unit, started the car to go tune it and boom, engine noise is back. At this stage i was very annoyed because i couldnt understand why it had started again when all i had done was screw it in.

Started to further troubleshoot and long story short i found out that the only thing left that was causing the popping + Engine noise was when the screw was placed on the metal plate.

At the moment the unit is only being held in by the A/C fascia which is OK but its not secure.

Last bit of info to hopefully allow people to help solve my issue; The wiring harness has been messed around with at the back of the H/U (+ve -ve acc) when i was setting up my mirrors. This has now been removed, however is there a chance that these connections may be damaged, if so could this be causing the issue.

Questions:

1) Why when i place a screw into the bracket does it start to pop

2) Is it worthwhile grounding the bracket its self

3) I grounded the RCA's to the ground on the harness, would it be better trying to find a ground point on the chassis

4) Any thing else

Apologies for such a long winded post; Hopefully some of you guru's can help me out

[123R-Prozak]

dont blow up at me, but while i wasnt paying attention in class, my teacher said that the alternator can make that noise through your speakers....

either the rectifier? or voltage regulator ?

* STAB IN DA DARK ! *

[Brad!]

Yer i know what the noise is, and i know how to stop it (Not secure the headunit)

My question is why is it happening, and what is the correct solution.

Does my head unit chassis/cradle be grounded cause i have some rubbish power issues (Exposed wires etc)??

[chicken]

have you tried no. 3? ground RCA to chassis