Speaker interference when car is running.

[wenman]

I've read up a bit on this and have a fair knowledge of installing speakers amps etc in cars, but in my Ibiza I have run all cables neat and tidy but have interference coming through the speakers when the car is running.
I have the power cable run down the left hand side of the car,
the remote cable is running down the middle
the RCA's running down the right hand side,
all speakers cables are run down their side of the car (components front and back)
and the earth is joined to the original earthing point behind the carpet on the left hand side of the boot.
I have two separate amps, a 4 channel for the comps and a mono for the sub.
My first thoughts are power cable being too close to speaker cable and existing wiring in the car, (under the carpet).
The earth could need to be to a more solid place giving a better earth.
Or RCA's run too close to speaker cable and existing wiring.

Could anyone please help to isolate the problem so that I can get rid of the interference!
Also will it matter about wires crossing in the boot? it did not seem to make any difference in my old car.
Cheers.

 

[mt audio]

how have you attached your amp?directly to metal?if so itll be looping the earth.is it just one or both doing it?

matt

 

[wenman]

Hi Matt

Both mps are screwed down into MDF,
and its coming through all speakers (I have components front and back.
cheers

 

[mt audio]

have you tested your battery voltage when running?

where have you attached rca's?have you got an loc (line output converter) to do so?

 

[wenman]

rca's are straight from head unit to the amps, sorry but im not quite sure what you mean!
And as far as i know i don't have an loc.
and I havn't tested the battery voltage but i will get this checked as soon as its on the road

 

[stevei'D]

This should fix your problem.
Is you head unit earthed through the standard ISO block?

If it is cut the loom on the Head unit (not the CAR loom), when i say cut the loom I mean just the earth!
Join with new cable and run to the same earthing point as your amplifier(s) in the boot.

If you cut your head unit loom it can always be rejoined as good as new again. Obviously to save all the hard work first, connect and run thorugh the car over the seats before plumbing it all in under the trim.

Solved
Steve

 

[wenman]

The head unit is connected to the standard car loom, so simply cut the earth on the head unit and run to the amplifier earth?
Does this stop any loops then?

Thanks i will give this a try

 

[wenman]

Tried this one Steve but it had no effect thanks

 

[mt audio]

you havent said whether its only doing it when engine running?tested the battery?

 

[wenman]

It's only when the engine is running, when it's not there is not interference at all.
And the battery is pretty much new i think, so test the voltage are you saying?
what difference will this make?
Thanks

 

[mt audio]

if you test the voltage when its on tickover and also when you rev it,it shouldnt jump any higher than 14.4v anything higher is the alternator overcharging causing interference

 

[BigWill]

Does it get louder as you rev? If so that's alternator whine

 

[wenman]

Yea it's deffinately alternator whine but i just cant find the component causing it, i've trid rerunning the power cable away from everything(under the passenger seat) I also moved the RCA's away from evrythingbut the noise is still there. I have removed RCA's from both the head unit and amp (one end at a time) and the noise stops, does this indicate it's the RCA's?
I've also re-earthed the headunit directly to the battery.
The amps are both earthed to the panel behaind the rear quater carpet but not using the original earth there, they are earthed below this and both earth cables are between 6 - 10 inches long.

Does this help at all?
Thanks

 

[mt audio]

what voltage are you reading when you rev-you need to check this!no point checking anything else till you have as if the voltage is too high then the alternator needs new brushes and is overcharging

 

[wenman]

I will find this out in two weeks when its on the road thanks for all the help