Thread: BAD engine intereference PLEASE HELP

It sho iz not....

Some amplifiers have isolated ground systems where the audio ground is seperated from the power ground.

My advice is to start simple. Pull out the Y connector and plug the audio cables directly into the head unit. Is there still noise? Plug it into the TV, is there noise now where there wasnt before? I have to warn you that the components of that DVD player are on the low end and subject to noise issues like this.

Basically what I am saying is start cutting out variables and see what happens. Locate the noise source and then work from there.

There are too many different problems here to address each one so I will try to simplify this for you guys. This is how I wire all my installations that involve multiple pieces of electronics (keep in mind that I have done this at least a 1000 times). First, I run a power wire directly from the battery to the rear amp. Then a power and ground wire from the rear power supply line to the front of the car (generally the head unit and stuff is here modify this for other installs). I do not use a direct ignition wire for anything. I wire a relay to change constant power into ignition power. I use the power wire ran from the rear to front to power the relay and electronics. I use the ground wire from the rear to ground everything. Keep in mind the current draw to determine the wire gauge needed. Then I use a digital multi meter to test for a good ground location in the rear. Once I find the ground location I ground everything to this point...all amps,head units,eqs, and such. Only thing that does not get grounded there is relays.

I hardly ever have noise...1 in 20 installs. Over 15 years that is pretty good. Also I never use ground loop isolators. If you take the time to find the problem there is no need for one.

How to wire the relay to switch ignition. 85 goes to ignition, 87 constant 12v, 86 to ground and 30 to radio ignition lead.

How to test for a good ground with a digital multi meter or VOM. Set the meter to continuity or impedance (measures in Ohms). You will need a long piece of wire to get from the front of the car to the rear of the car. You will also need to either ZERO OUT the meter or take into account the resistance of the wire. Attach the wire between the two contacts. Zero out the meter or write down the amount of resistance the wire has. Now attach that piece of wire to the negative lead of your VOM and the other end to the negative battery terminal. Take the positive lead and touch it to potential or current ground locations. The impedance should be as low as possible. The higher the number the more likely you will have noise in the system. You can use this procedure to test a current ground location or to find a new one. Let's say you find a ground location you know should be a good one. Like the frame of the car. Your meter reads high impedance. You can then change out the factory negative cable or add another cable to the factory line. Make sure the cable has a good clean and tight connection to the battery and chassis ground. This will lower the resistance to the rear ground location. Using this procedure combined with proper wire gauge sizes will allow maximizing ground locations and minimizing possible noise injection.

When you have multiple pieces of electronics and noise it is often best to determine which piece of electronics is causing the noise. Start by removing products one at a time. If there are electronic EQ's or xovers bypass them. Eventually you will find the piece that is making the noise and be able to concentrate on the piece.

I have never found a noise in a car that could not be removed with proper grounding and power supply. Or it was a bad piece of electronics. More often then not it is a power/ground situation and can be solved with a little time.