- Sun Jul 27, 2008 2:33 am
#63475
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.