alternator size

[DButler]

OK so I am having problems when I drive my car and turn it off it will not restart. The holley HP will not fire with less then 12 volts. I have a yellow top optima battery. I currently have the holley HP ecu...electric black magic fan...areomotive a1000 pump...Msd...stereo...gauges etc. I can hook jumper cables to it and it will fire right up so I know its the alternator not charging or battery. When I am driving my gauge is showing 14 volts so either the battery isn't being charge or alternator isn't charging or isn't big enough...I keep a battery tender on the car. I think the alternator is 60-80 amp chrome one wire. May be a 100 but I am not sure. Should I go with a bigger alternator? Is it too small to keep the battery charged with all of my electronics? Any help is greatly appreciated.

[ccmc]

What's your idle speed. You will spend a lot if time at idle and the higher amp alternators tend to charge less at idle. I had this same problem. Bought an overdrive pulley to spin the alternator a little faster and it's been running great for over a year

[DButler]

When you say idle speed are you referring to rpm? If so it is 1000

[Thephranc]

Are you sure its not a heat soaked starter?

[DButler]

Yes pretty sure its not that because as soon as I hook the jumper cables up it will fire right up...the ecu requires a minimum voltage to start (either 12 or 12.5) gauge will show 12 when I turn key on but when I whirl it then it drops to 10 or below...when I M driving it shows 14 and when I park and turn off it want crank most time because voltage..bit gauge shows it charging so I think its either battery is not holding charge or alternator is not charging enough to keep the battery up

[reschke18]

One wire alternators are notorious for not charging well at low rpms. You have to wing the throttle to get them to charge, or like stated earlier spin them faster. You will be far better off to wire it up with the normal three wires. You can most likely use that same alternator, just pull the block off plug out from where the alternator plug goes, and get a alt plug and wire it up.

[astroracer]

One wire alternators are notorious for not charging well at low rpms. You have to wing the throttle to get them to charge, or like stated earlier spin them faster. You will be far better off to wire it up with the normal three wires. You can most likely use that same alternator, just pull the block off plug out from where the alternator plug goes, and get a alt plug and wire it up.

X2 on that response. Wire the alternator as it came from the factory. ALSO make sure your wire sizes are more then adequate. Small gauge wire will cause resistance as it heats up and make the problem worse. I would wire all of your charging circuit with at least 8 gauge and would go as big as 4 gauge if the battery is in the back.
If the alternator is only a 60 or 70 amp unit you may concider upgrading to at least a hundred amp. It will be marginal at this point with "good" wiring so, if your wiring needs some attention, this would be the time to address the whole system.
Mark

[DButler]

I am not sure how to wire it like original. I had a new painless wiring kit installed in the car a few years back. Also I never had this problem before. The last thing I have installed was a stereo. I have never had this problem before so I am wondering if the battery is just going bad and won't hold a charge it will fire right up when the battery tender is on it.

[hessdawg]

I have had allot of problems with optima yellow and red tops not holding a charge
I would take it to an auto parts store and have the battery and charging system tested

[DButler]

What is a good batter to replace the optima? Anything that will fir in the optima battery bracket?

[ol green]

With all the pull you have on your electrical system-fuel pump, amp, MSD, etc, when you add all that up and the lack of low rpm charging of the one wire, you need a bigger alt. Your elec fans can pull 50 amps and you only have an 80 amp alt to feed all this. I wire a lot of hot rods , the smallest alt I will put in anymore is a 140 amp. It makes life easier---my.02

[DButler]

OK. Can you tell me what the first test to run to determine if battery or alternator. I would rather spend money in the right place to fix the problem. Should I take the battery and have it tested?

[DButler]

My car did this when driving also cruising at 2500ish Rpms. I wasn't sitting idling.

[ol green]

you bet, do the battery first, however the fact still remains on all the load you are putting on that alt..check how many amps all those electrical components need, you will be surprised for sure

[DButler]

What a good 140 amp alternator? I really don't want to rewire car. It is SBC with march system

[DButler]

battery checked out to be good. So what is the next test?

[TheJDMan]

You really need to read some of the electrical tech articles on Mad Electrical's site. There is a lot of good information on how the charging system is supposed to work. He also has an article comparing the single wire alt to the three wire. After reading his articles, I decided to convert my single wire alt to a three wire alt by changing the internal voltage regulator and running a dedicated sensor wire.

http://www.madelectrical.com/electrical-tech.shtml

[dontlifttoshift]

It will not start or will not turn over?

[DButler]

Great. I will read that info. It will turn over but just spins because the volley HP efi requires 12.5 Volts to crank and obviously the battery doesn't have that much because I can hook jumper cables to it and it will fire right up. When I turn switch on it shows 12-13 volts when I whirl it over it drops to 10ish and then when I'm driving it is charging at 14ish. I just had battery treated three times and it checks out good.

[ol green]

What a good 140 amp alternator? I really don't want to rewire car. It is SBC with march system

contact March to find out what fits their brackets, the Mad Electrical as mentioned is a great site, lots of good info. as for alternators, Tuff stuff has quality US made parts, have had no problems with them at all