okay, when I have my heater on, and I have my sub on, and I have my rear defroster on, I notice my windshield wipers go about 1/2 the speed they should. It's like my alternator isn't producing enough power.

I think I need a higher powered alternator. Is this right? But if I get a higherpower alternator, do I have to change any wiring in my car? And where would be a suitable place to buy a better alternator from (other than ebay)? If this even is the solution ot my problem.

 

well how big is your amplifier?
if its under 1K watts the stock alternator SHOULD be powerfull enough..... but most likely your grounds are preaty crapy. i would upgrade your ground wires to like 4gauge wires, frame rail to tranny passenger side, power steering to front front radiator suport... and if thats not enough upgrade the alternators power wire from the alt to the battery to 4gauge. and just clean up your battery posts as well. sometimes the posts just get coroded and limit current....

 

Too difficult to tell with such little info
chances are with the type of car you have that it puts out 75 cranking amps from the alternator, this puts out 1080 watts RMS worth as long as it is continuously putting out 75 amps at 14.4 volts
Even at this point if you used an amp that was rated at 1080 watts RMS, had your lights on, heater and wipers, everything should run fine, just a bit dim in the lights.
I personally do not think it would be your alternator but it is really hard to tell without you telling us your ground size, amp rms range, and a few other small aspects

 

1080 watts will chew up EVERY amp of that 75 amp alt. all by it's lonesome. Add some of the CARS actual needs..... the math doesn't work out, at all!
You will need a bigger alt. Check it out!

 

I would check to see if your alternator is working to it's full potential.
I'd also check the alternator belt tension to see if it's within specs and to clean up all your grounds.
those are the most common problems.

 

My amplifier is exactly 1080 watts rms and has little problem with lights, amp on, heater etc.
Don't get me wrong, it's not good for the alt., produces a lot of strain, but it can do it
The math does indeed work out because remember, not every ampere is also coming straight out of the alternator...if so then this would be a problem
in fact my battery came undone once and everything the car ran on was straight from the alternator, at about 500 watts drain from the amp is when the car had a mound of trouble, things i never want to see or hear again
The reason i use this example is not in the least saying it's ok to run a system like this, it's not, but im using this example to show he'd need quite a lot of draw from the amp in order for his wipers to slow so much, unless there's another electrical issue I haven't considered such a power supply for defroster and wipers and heat running in a straight circuit

 

Heater (on high): 25 amps
Rear defroster: 20 amps
Wipers: 10 amps
Headlights/tail lights: 15 amps

You're pretty much at the limit of the alternator before you even turn on the sound system.

 

well another thing REMEMBER your amplifier doesnt pull MAX POWER all the time.... simply turn the stereo down.... it wont pull as much power. very simple quick fix

at least until you do upgrade your alternator....
easiest thing to do is look in your phone book for a alternator/starter rebuild shop.... but ebay ones will get your best price cause some shops will charge INSAIN prices just cause THEY CAN..... but some shops are very cool.... i know my one small alternator shop is preaty good on pricing and ive heard another alternator shop charges insain prices for the same stuff... but you dont know until you call a few and ask for some quotes and compare to ebay prices. me personaly ive been planing on buying from ebay myself eventualy that is...

 

what class amp do you have? class d? or ab?

 

When I was running my system I never got a high power outage Alternator, I just went and bought a optima battery(Dry cell battery)(either a yellow top or blue top)make sure and connect it to the main battery (both posts) then run the amp through that battery. Also put a ground to the chassis from the second battery. I know the price went up on them though so they're kinda spendy.