Cap or Alternator?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=16349
Printed Date: September 11, 2025 at 1:04 PM
Topic: Cap or Alternator?
Posted By: pc_man83
Subject: Cap or Alternator?
Date Posted: July 15, 2003 at 8:35 PM
Hi guys, Here is my situation. I have a 1998 sunfire coupe. I know this stuff is old, but it still works good. I have a mtx 1502 amp pulls about 350 watts and a 12" rockford fosgate 12" dvc. Now when I crank up the music my lights dim and my dash dims. I work at circuit city and the roadshop guys say a cap should fix my problem? I think my little 65amp alternator just wont push enough. Give me all the input you can. I am also planning to add another amp later for my highs. Oh and a have a 50x4 alpine 9807 reciever. Mike
Replies:
Posted By: nedgeworth
Date Posted: July 15, 2003 at 9:05 PM
Well i would suggest a HO alternator. You will get many different reply about this. You can by a cap seeing as it is a lot cheaper than an alt.... but it maybe not solve your problem... as well as putting more load onto your charging system... i think it is safer to go with the alt seeing as your looking at adding another amp too your system.
Posted By: wvsquirrel
Date Posted: July 15, 2003 at 9:27 PM
I agree. You'll be better off in the long run if you invest in a HO alternator now. Cap's are not cure-alls (even though there are still some people out there who believe a cap will fix every power problem imaginable). A HO alternator will provide you with the amperage that you need to properly run your audio system, as well as the rest of the vehicle's electronics. Especially if you are planning on adding another amp, which is only going to increase your current power drain.
Don't get me wrong, adding a cap can help, but it will not "fix" the problem. If anything it will only act as a bandaid and the problem will get worse. Using a Cap in the proper circumstance can help even out voltage regulation for better SQ. But it will not fix your power problem. ------------- Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
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Posted By: MAXST
Date Posted: July 15, 2003 at 10:08 PM
Both would be they way if you got the money. the cap stores and lets lose under a heavy hit...
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Posted By: pc_man83
Date Posted: July 16, 2003 at 4:52 AM
Thanks, not what I wanted to hear but at least its the truth. How big of a alt should i get, would a 105 amp do? Becuase auto zone carries duralast ones. ALso wont a higher end alternator cut away from horsepower?
Posted By: MAXST
Date Posted: July 16, 2003 at 8:02 AM
First calcaulate your loads and current amp draw with everything in use...then use that number to go off of to pick your alt.. ------------- I need quality equipment, feel free to donate.
Posted By: pc_man83
Date Posted: July 16, 2003 at 8:52 AM
How would I go about doing that? How do i measure amps would I have to put a multimeter in line with the amp. I am pretty sure that would blow the meter. MIke
Posted By: bberman1
Date Posted: July 16, 2003 at 11:43 AM
Add up the RMS of your total system then divide by 12.7. So if you have 800 watts rms total and then you divide by 12.7 you will get around 62 amps. So you would need an alternator that puts out 60 amps more than your stock alternator (just an example)
Posted By: Big Purds
Date Posted: July 16, 2003 at 1:50 PM
a higher output alternator will take add a little more resisitance to the pulley and therefor probably draw a little more power to turn, but lets face it, a Sunfire isnt exactly a racecar...
basically you can look at it like this...you can have a fast car, or you can have a loud car...to make both out of a sunfire is very unlikely to happen...
a cap is not really for use as a "backup battery" as much as everyone claims it to be, but more as a voltage regulator, to even out the drops and spikes that happen in your electrical system, and shouldnt really be used in any megawatt system...its basically doing more harm than good until you have a high output alternator, and once you are at that point, a cap is redundant...
dont waste your money on a cap, invest it into your electrical system...before you replace the alternator, try upgrading the leads on your current alternator with 4 ga...it may help out...
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