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Discussion Starter · #1 ·
i have a 73 mustang with 351w and the alternator just a replacement alternator for my original cleveand. (somehow dad mated the two to work) or is it the same alternator?


well i think it is a 55 amp alternator is stocked. correct me if i'm wrong. will (2) 600 watt amps fry the alternator?

am i looking at maybe a 100 amp alternator or maybe a 130 amp?
 

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A low voltage/amp situation is bad on electrical/electronic components. I would give a call to someone who installs the car stereo's/amp's and get their opinion. My .02 is not only will you possibly fry the alternator, but you could fry some wiring and your amps.
 

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IF each amp was CONTINUOUSLY drawing 600 Watts (which it won't... that's just the peak draw on big 'thumps' with the volume turned up all the way) then 600W on a 12V system is 50 amps.

Will the stock 55amp alternator keep up with two of those amps... and the rest of the car's electrical system? Probably not, if you are always playing the radio very loud. Will it 'fry' the alternator? Probably not, as long as you aren't spinning the engine 5k rpm while the alternator is under full charge.... but it will drain the battery dead.

You'll want to either get a larger alternator, or add a second battery for more 'reserve' capacity. Maybe both if you like to drive around slowly at night with the volume up all the way. (I'm getting a headache as I type)


Power (watts) = volts x amps

amps = Watts/volts

I'm not into the car stereo thing big time (I did install a nice system in my brother's Jeep with a crossover and two amps) but know a little about electricity... enough to know that it's better to have extra capacity and not need it... than to need it and not have it. Electrical devices don't like running on less voltage than they are designed for... and this occurs when the battery gets low and you KEEP drawing a lot of current through it.

I bought a 100 amp one wire alternator that looks just like the original mustang unit (except it's chrome)
to run my electric fuel pumps, water pump, fan, ignition, nitrous solonoids, etc. They only had it in chrome, and it cost around $170
but was one of those necessities. It works just fine.

Good Luck!

_________________
Mike Burch, 66 mustang real street
302 4-speed 289 heads, 10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367

<font size=-1>[ This Message was edited by: n2omike on 6/3/02 9:05pm ]</font>
 

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I have the stock 65 amper in my Mitsu and I run both a 800 and 550 watt MTX amps and it keeps up just fine and I spend most of my day in the car. The blower motor is more of a draw then the amps are (this I can tell from when my alt belt is loose..it never squeels from the stereo but sure does with the fan blower on. The only time you pull max power is on extreme peaks of bass which is momentary at best. If you have it cranked up enough to run it down then you will have more serious trouble then your alternator. You will find alot of myths about alot of things in the car stereo world especially when it comes to wires.
 

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It really depends on the amplifiers power supply and current draw. If the amp has an efficient class D regulated power supply it might be alright, but if either amp is class A or class A/B then you're definately going to strain everything if it puts out a true 600 watts peak. I recently installed a MMATS D100 in a friends '93 Explorer along with a pair of 12 inch Kicker subs. The amp is rated 700 watts @ 1 ohm and the power supply is class D and it'll kill the engine if you crank the stereo up with it idling. You can rev it and hold it at 3-3500 rpm and the stock alternator still doesn't supply enough voltage to run everything as the lights dim horribly and the volt gauge still goes crazy... but we're installing a 6G powerstroke alternator on it in a few days along with about 3 farads of capacitors to stop the voltage problems.
On my Galaxie I've got a 250 amp HEHR Powerline alternator with an adjustable regulator.. I can juice it up to 18 volts if I need to.
 

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I say it'll be fine, but, your headlights and everything else electronic will dim really bad. Get an extra battery or better yet a 1 farad capacitor which holds enough reserve for 1000 watts to be pulled out, a good 1 farad cap runs about 70$. Also, when running those subs, its going to take amperage away from the spark for your engine, meaning bad performance, and possibly killing the engine while idling. If you decide to replace the alternator, which is a better fix, but more expensive, make sure all the harnesses in the car are ready for the bump up in amperage, so you wont melt the insulation on the wires, its happened...
 

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I had a 1200 watt Power Acoustik amp on my F-150 with a 130 amp 3G alternator. It would BARELY move the voltage needle on my truck at full blast, so I think I had enough power. And I had the same prob, the electric fan I put on the truck pulled more power than the radio did 99% of the time. The only time I got the radio to drop the voltage as bad as the fan, was when I cranked it up and played a bass test CD. It made my mirrors viberate so bad that I couldn't see out of them! The cop that was at the gas station wasn't impressed either, he made one of those turn it down NOW motions with his hand. Just glad I didn't get a ticket!
 

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Discussion Starter · #8 ·
so if i put a 100amp or 130 amp alternator i will have to do what to the harnesses and wirng? how will i tell if my wires won' melt?
 

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I'm not quite sure on that one, I just know that it has been an issue for people, whatever you did, the end result would have to be more insulation on the wiring, or bigger gauge wire... My Dad told me about a buddy of his who blew his entire electrical system because the harnesses werent up to par, unlikely, but would suck if it ever happened.
 

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On 2002-06-04 02:32, XolieX wrote:
so if i put a 100amp or 130 amp alternator i will have to do what to the harnesses and wirng? how will i tell if my wires won' melt?
Run a charge wire off the back of the alternator directly to the battery. Use 4 gauge, crimp and solder the ends well, and put the other end directly to the battery + terminal or add a distribution block first and then split it to the battery and also the amp. Also, make sure all your grounds are AT LEAST the size of your primary feed wire.
For an easy 100-130 amp alternator check out a 10SI or 12SI GM unit, they're readily available as a one wire unit that doesn't require any wiring other than one charge wire.
 

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On 2002-06-04 01:09, BuiltFordTough wrote:
I say it'll be fine, but, your headlights and everything else electronic will dim really bad. Get an extra battery or better yet a 1 farad capacitor which holds enough reserve for 1000 watts to be pulled out, a good 1 farad cap runs about 70$. Also, when running those subs, its going to take amperage away from the spark for your engine, meaning bad performance, and possibly killing the engine while idling. If you decide to replace the alternator, which is a better fix, but more expensive, make sure all the harnesses in the car are ready for the bump up in amperage, so you wont melt the insulation on the wires, its happened...
If the lights dim and the voltage drops badly then it's NOT fine.
It'll work, but it'll strain the charging system. If you add a second battery add a battery isolator and wire it so the stereo only gets it's power from the second battery. With the isolator inline the alternator will charge both batteries but the amp will only be able to draw current from one of them. That way if you have voltage problems it won't affect the entire vehicle. you'll be able to discharge the stereo battery, yet the vehicle will still start.. it's great if you have a habit of listening with the car not running. Adding a cap is also beneficial, but onlyif your battery and alternator can suppy it quickly after it's discharged. If your alternator can't throw power back into it quick enough then the cap also becomes a draw on the system and the power to the amp will suffer more.
Instead of a cap, check out the XStatic Batcap at http://www.batcap.net It's a battery with the discharge rate of a regular capacitor.
And it doesn't cost that much more than a single 1-1.5 farad cap.
 
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