Yet another noise problem

Hi,

A few days ago i took my 2000 Jetta to have a deler install a MTX Thunder amp and a Sub that I used to have in my previous car. I still haven’t bought a new head unit so I used the original car stereo to feed the amp for now.

Everything seemed to be working fine but yesterday I noticed that whenever the car is turned on and stopped some noise is heard on the speakers and sub, this is most noticeable in the sub that in the rest of the speakers. The symptoms are the following,

I also noticed that, at night, sometimes the car lights lightly blink when the car is stopped. Since I changed the car battery a couple of months ago, I assumed that the entire problem might come from my alternator.

After reading posts regarding noise for about two hours I decided to do some basic testing on my system in order to confirm my thoughts about the alternator being the cause of the problem. This is what I did,

- Checked the cable runs. The power cable is run thru the driver’s side and the input RCAs on the passenger’s side

This made me think. If the problem was the alternator inducing noise on the amplifier power feed, I would get noise on the sub whenever the car was turned on regardless if the car stereo or my laptop was feeding the AMP.

My newbie conclusion is that the problem may be related to two possible causes,

Well, anyway if somebody has any idea or thought on what can I do to solve this problem it would be greatly appreciated

First, I want to congratulate you on an well-thought, informative post.  Many times users will only give us symptoms, and want a quick solution to their problem.  At this same time, they'll give us no description of make/model, what gear they have, what they've tryed so far, etc.

You should really have the stereo shop take a look at it.  Since they installed everything, check with them and they should have a solution.  You shouldn't be charged anything, since you didn't do anything that would have caused it.

If you do want to just fix it yourself, it sounds like you've actually done the hard part, and narrowed the noise down to the signal input.  Since the amplifier in this car is below the rear deck, on the passenger side, I'd check to see if they got signal there first, or perhaps the rear speakers.  Many times line-out-converters will come with a couple wires that you can ground if you have noise problems.  I've never used these before.  If these wires are grounded, try disconnecting them (tape them off so they can't touch to ground) and see if the problem goes away.  Ensure all the connections are good.

It could be a bad ground