#1 how many amps will a good system draw? a 200w head unit, 1000w or high amp, 2 12s, etc. Is a stock alternator good for a good aftermarket system? And #2 what does the alternator need to be hooked up to work correctly? which wires and what voltage? cause my car dies down(low voltage) when i turn the volume up and the battery light is faintly on all the time, but it always starts up. I think one of the wires is off or missing. I know it has the 2 wire pig tail, the one red wire at the back, and the ground. What does the pigtail and the red wire at the back do? i know the ground, but are the rest 3 positive wires? thanks, Joe

 

1)
From Ohm's law; I = P / E
I= current in amps, P= power in watts, E = electromotive force in volts
So in your case: I = 1000/13.8 = 72.46 AMP, are needed to drive your system @ 1000 Watts
Considering that stock alternators are sized only slightly larger than needed you should still look to install one capable of producing 70 amps more than the one you already have.

2)
Do not wire your system directly to the alternator, too much electrical noise.
Usually there are a minimum of 3 wires.
Ground, to complete circuit
Continuous battery, to preserve your settings
Switched battery, to provide power to the system when the key is turned on
Other wires to operate antennas, amps, etc..

You really should get the instruction sheet that came with the system.

 

I was asking about the wires that plug into the alternator, not the stereo. The stereo works fine. The car gets all effed up. But even with the stereo off, there is a constant battery light on, but very dim. So i was asking where do the 2 pigtails on the alternator go, and what does the red wire on the back do? they are all hooked up but i think there is a break in the line somewhere down further, so i want to know what to do to fix it or findi t. BTW, this is a standard small block alternator, 84 z28 HO.

 

The alternator should have3 wires/cables.
Red/Orange or Black/Red going to the battery (B+)
Brown or Orange wire going to a isolation diode and then to the instrumentpanel (L)
Another Red/Orange or Black/Red strapping the (B+)to the remaining trminal on the alternator (S)

 

ok so the one that goes to the dash might be why my light is always on? I think the light burned out today too because now it doesnt come on at all.

 

There is an isolation diode connected between the wire going to the dash and the battery lite. The isolation diode allows current to only flow in one direction, and is connected so that when the battery voltage is higher than the alternator voltage the light will go on (battery discharge condition). When the alternator voltage is higher than battery voltage, the light will go off. (normal battery charging state). If the diode shorts out the light will be on at all times and run the battery when the engine is off.