interference after fitting amp

[HKS_JUN]

need a some help peeps fitted a amp in the car works fine with no interference when the car is turned off.
as soon as i start the car it has interference it has got a good earth. i havent got a sub wired just 2 rear speakers anyone what the problem could be

thanks in advance

[SOHCivegra]

Check oout where your power wire is running. You could be picking up signal interferance if you RCA wires are running next to the power wire. To be on the safe side I have always recommended to run your power, 12V signal and earth on one side of the vehicle and the RCA wires on the other side.
Check those out and see if you have this issue.

[swich]

SOHCivegra: you beat me to say that... but you right.

[HKS_JUN]

thanks will try that today hope it will work cos i have been trying to get it to work for afew days and not had any look

[HKS_JUN]

ok i have tried this but still have the same proble

anyone what it could be

[SOHCivegra]

do you or did you have cheap RCA wire installed. If they dont have a good coating around the wires inside them they can pick up signal from the other wires. Also you can check your engine earths, if you have poor earths on the engine you could be picking up the interferance from the engine and not the sound system.

Do an overall check, mainly interferance is caused when something in an entire system (including engine components) has a poor connection. You can also check the strenght of you battery, if it is to small and cannot produce enough for the amps needs then this will cause a poor connection between your vehicle and the charging system.

[HKS_JUN]

will check this hopefully willwork

[SOHCivegra]

Hopefully this works, i'm staring to run out of diagnosis ideas here.

[asianrob]

run the wires away from your cabin harness it could be picking up from that like you can run it like this power and remote on one side and RCA on the other of the tunnel under the carpet where your shifter and arm rest would be. doesnt have to be in that exact order.

[HKS_JUN]

still not working tried any other suggestions

[suspendedHatch]

Ignition noise is almost always caused by a poor ground. You say you have a good ground but I have had all kinds of customers come in with this problem and say they have a good ground that their friend/cousin etc hooked up only to find that their ground is laughable if not an outright insult to professionals like myself. So forgive my skepticism.

A good ground means that the ground wire is short and the same gauge as the power wire. It will be grounded into the frame into the car, not a piece of sheet metal that is mostly held on with caulk and spot welds, ie the floor boards. The paint beneath the ground's ring terminal should have been removed by a wire brush attachment on a drill. Not just to the gray primer but to the shiny metal. It should be held down with a star washer (aka lock washer) and enough metal tapping screws to ensure that it will not move. DO NOT USE A FACTORY BOLT ie seat belt bolt. You can verify that your ground is good by measuring the resistance between your ground point and the negative post on the battery with a multimeter. It should be less than an Ohm. Also be sure that the ground is pushed all the way into the amp and held tightly.

Another thing that I like to do to prevent a ground loop is to run a 18 gauge wire tapped into the stereo ground all the way back to the amp's ground. There's no excuse not to since you're running a remote turn on.

Speaking of the stereo ground, factory grounds are usually pretty noisy. On my personal car I branch off the factory ground and use a ring terminal to ground it to the firewall.

The next most common cause of ignition noise is a bad amp.

Third most common problem I would say is bad RCA's. If you're amplifying mid bass speakers you really should drop some extra money on the RCA's. Although with a proper installation with good equipment, you should be able to use only decent RCA's and not have a noise problem. But exceptional RCA's can make life easier.

Fourth most common cause I would say is a bad battery. If you've ever let your battery go dead, it may seem to work just fine after a recharge, but in fact you have cut the battery's life in half and also damaged it's ability to filter alternator noise.

Fifth most common cause I would say is bad plug wires.

Theoretically a bad alternator could cause ignition noise but I have not had this problem.

I have never used a noise filter. They cause more problems than they fix and only serve to mask the problem at best. If I ever got this far w/out solving the problem I would probably try running a 12 gauge wire from the amp's chassis ground directly to the negative post on the battery.