7th Heaven

Here is my problem, the previous owner of my car wired the radio (and amp and 10" bazooka) so that it manually turns on and off (not with the ignition) and it basically runs off the battery, i.e. if you leave the radio on overnight the next morning you're going nowhere. My thing is that at night when I have my headlights on and the radio, my dash lights dim when I hit the breaks, my radio face plate dims everytime the bass hits, and when I hold the brakes down to slow down, or at a stop, sometimes the bass just cuts out, I take my foot off, bass comes back, and my dash dims up a lil bit. So could it be my alternator not keeping a good charge or my battery needs changing? Or just the fact that my radio and amp and sub is not wired like it should be? When I'm cruising (like above 2k rpm) the dash lights are nice and bright and my faceplate doesnt dim as much, but when my car drops in revs i.e. idling at a stop, its like the alternator isnt charging the batter as good as it should. I have a boat battery also if that helps.

fcvenom

Man the same **** happens to me every time i drive at night. I was told that it's the alternator but I checked it and it was fine. I turned off the radio and it kept happening over and over again. Does the same thing happen to your boost gage

WAYNE88N/A

Might need to upgrade the alt- Mazda didn't design the S4 electrical system with 2 million watt stereo systems in mind, lol

7th Heaven

"Does the same thing happen to your boost gage"
Nah, car's N/A.

By upgrade do you mean buy a new OEM alternator or get an aftermarket one made especially for my (our) car? Where would I look for an aftermarket alt? Also, I do have aftermarket fog lights tapped into my headlights, I bet that doesn't help at all..

fcvenom

I don't have a bazooka or anything complicated my stereo system is pretty simple. All i have is two small aftermarket speakers and a new radio, and this light problem never happened before. I've been driving the car for 3 months now. The problem started about 3 days ago

WAYNE88N/A

SilverRotor was selling plug & play FD alts for our cars, but I don't know if he has any more...

Maybe PM him?

You can also use an S5 alt, but the wiring is a bit different at the plug on the back of the alt, I believe...

7th Heaven

Same here, the amp is only 350 watts and the bazooka tube isn't all the big. But anyways, thanks Wayne, i'll search around for a new alt, shouldnt cost to much.

WAYNE88N/A

Let me teach you a little formula here. You say "only" 350 watts, right? Watts is power consumed, written as a derivative of ohm's law, the formula is P=EI, or power (in watts) equals voltage times amperage. Now, since we know the voltage (let's just use 12v to make it easy), the formula becomes 350=(x)12, or 350/12=(x)...Which comes out to...29.16 amps.

Now, the S4 alts are rated at a minimum of 55 amps, continuous, at 2500 rpm (or about 1250 engine rpm), and a steady state peak of 70 amps...

In plain English, your stereo system is sucking down damn near half of the total output capacity of your alternator...Add your headlights (55w apiece=9.2 amps), your brake lights (5 bulbs totalling 135w=11.25 amps), and the power it takes to keep the car running via the ECU (I'm guesing at least 15A here), and explain to me why you're baffled that your lights are dimming with the bass beats...

7th Heaven

So you're saying I have to do weight reduction stage 2: ditch the tube and amp? =)

Does turning the volume down at all help, it's already pretty damn low to begin with. I even turned the bass all the way down.

WAYNE88N/A

Do a search for "upgraded alternator", man, you'll be reading for a while...This question pops up at least once every two weeks...

Or if you're getting old like me and just don't jam as loud as you used to, ditch the system

95R2-89TII Ground Zero

Okay, my advice:

1. Take the bazooka out
2. Upgrade the alternator(read #3)
3. Upgrade the battery.......only if you are gonna put a system in the car