Car Stereos: Car Speaker Static, static interference, carbon monoxide poisoning

Question
QUESTION: hi,
when i have my car engine off, the door speakers can go as loud as you want. however, when the engine is on, the left hand speaker has loads of static interference when turned up to a medium volume. if the balance is changed to the right speaker then it has no static interference and can go reasonably loud, but when the balance is put back to the middle, there is a lot of static in the left and a tiny bit in the right one.
any help would be appreciated

thanks a lot

ANSWER: I need a bit more information before I can send you off in the right direction. First of all, is this a factory or an aftermarket system? If it's an aftermarket, please list the components you have installed and where they are mounted.
Secondly, do you have a factory charging system or has there been any upgrades like a second battery or heavy duty alternator installed?
Does the noise appear regardless of the whether you are listening to the radio or CD/tape/MP3?
Please respond with the info and I'll try and help you troubleshoot this.

---------- FOLLOW-UP ----------

QUESTION: the door speakers are new ones not factory ones. I have installed the door speakers using new speaker wires and they are innstalled on the front two doors (3 door car). I have a factory charging system and the sound occurs regardless of radio or cd.

if you need any more info juts ask

thanks again

Answer
This could be one of two problems. The first step is to verify that none of the speaker leads on the new speakers are touching chassis ground. It's very common for me when troubleshooting noise problems like this to pull a speaker and find that the tinsel leads on the speaker or the speaker terminals themselves are shorted out when the speakers were screwed into the door.
Undo the screws on the left speaker and while holding the speaker in your hands, turn the stereo with the car running (do this outside of course... we don't want you to get carbon monoxide poisoning) and see if the problem is still there. If it is, try the same exercise with the right speaker. If the problem disappears, ensure that the speaker terminals are insulated from the steel of the door. If the problem persists, you may have speaker wire shorted out somewhere between the door and the stereo. You would need an ohm meter to test this adequately. Is this something you have?
The second potential problem could be in the actual wiring at the deck. You said you ran new speaker wires to the deck. Is it a factory deck? If not, what brand is it and describe how you wired the speakers to it.