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Old 06-10-2019, 09:27 PM   #1
Cheyenne350
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Alternator problems

Im confused here with the problem I just started having not too long ago. I have 69 Chevy c10 with a built 350 ZZ4 heads, 750 demon carb XE284H comp cam. Alternator will drain the battery while truck is running and will drain it completely dead. Iíve done the trick where you turn on the truck remove battery alternator will stay running but once put into gear engine dies.

Iím guessing itís the alternator but asking around will say I have a short somewhere. Alternator is a 14 volts 100amps, asking summit racing tech support advice me to get a 12volts 100amps and that should solve my problem. Any help here would be appreciated thanks!
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Old 06-10-2019, 09:47 PM   #2
firedemon
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Re: Alternator problems

whats the idle speed when idol and when in gear ? assume its an internal regulator being 100 amps . 1 wire or 3 wire ?
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Old 06-10-2019, 10:12 PM   #3
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Re: Alternator problems

only 12 volts on a street engine will cause you problems especially if you have an hei ignition once you start using other electric stuff like headlights and things it will be worse . lets figure out why the regular alt isn't working its more of what you need
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Old 06-10-2019, 11:04 PM   #4
Cheyenne350
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Re: Alternator problems

Firedemon- idle speed is at 500 and its 2 wire hook up. In a way your suggesting not a 12 volts to get but perhaps more amps with the 14 volts I have?
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Old 06-11-2019, 07:10 AM   #5
Minkota
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Re: Alternator problems

As for stalling when you put it in gear, thats a pretty big carb, so I am assuming you have a decent size Cam. Does it have a Stall?
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Last edited by Minkota; 06-11-2019 at 08:02 AM. Reason: typo
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Old 06-11-2019, 08:02 AM   #6
Mike C
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Re: Alternator problems

Alternators designed/rated for a 12v system put out 14 volts. Usually 14.1 or 14.2 by design to charge the battery need higher voltage output than the battery. It sounds like the internal regulator is shorted in the alternator you have. Just replace it with an alternator of similar ouput.

You can also rebuild the regulator portion of the alternator and see if that doesnít solve your problems.

I like 12si alternators from an mid 80ís Suburban. Should be 95 amps and can be picked up brand new on Rock Auto for less than $100. Fits in the same spot as the 10si just the fan looks different.
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Old 06-11-2019, 08:13 AM   #7
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Re: Alternator problems

First thing I would do is to measure the voltage at the battery while running. If it isn't about 13.8-14.5 volts, the alternator is not charging. Take it to an auto parts store and have them test it.

If it isn't charging and it test good, look into the wiring, especially the exciter wire and the reference wire.
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Old 06-11-2019, 11:20 AM   #8
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Re: Alternator problems

I see you run electric fans, which suck a lot of juice. I would think a 100 amp if working and regulated properly should handle it though. Any of my vehicles have 14+ volts at the battery when running.
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Old 06-11-2019, 09:43 PM   #9
firedemon
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Re: Alternator problems

Quote:
Originally Posted by Cheyenne350 View Post
Firedemon- idle speed is at 500 and its 2 wire hook up. In a way your suggesting not a 12 volts to get but perhaps more amps with the 14 volts I have?
your idle should be 700 - 750 I believe in gear probably around 900 at idle. im thinking you probably have enough amps already unless your running electric fans and lots of other electric stuff . get the idle up and read the voltage at the battery should read 14- 14.5 if not check the thick wire post on the back of the alternator and see if its 14 or better again if not , check the brown wire for voltage on the 2 wire connector on the alternator it should be 12 or better . if the brown wire has power and crap for voltage on the rest the alt is bad if power is good on all you have something drawing it down witch is another fun problem . if no power on the brown you will have to trace it back and see where it is not feeding again fun
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