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Unread 08-31-2013, 04:26 PM   #1
rage4order
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1990 YJ Wrangler 
 
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Do I need an alternator?

I just upgraded my battery to an Optima Red top. I currently have a winch, aux lights, and a stereo w/sub connected. I'd noticed whenever I turned on my aux lights my voltmeter would drop. Also, when I ran my winch, my volts essentially went to 0. Hence the upgrade. Well, I swapped out batteries and started my Jeep. Turned on headlights, aux lights and A/C and my volts STILL dropped to about 8. Of course, when I give gas, my volts go back up to normal. Does this mean my alternator is bad or is something wrong with my battery?

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Unread 08-31-2013, 04:39 PM   #2
biffgnar
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Quote:
Originally Posted by rage4order View Post
i just downgraded my battery to an optima red top.
fify
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Unread 08-31-2013, 04:48 PM   #3
rage4order
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fify
Can't complain for the price I paid. And switching from a bottom-of-the-line Duralast, I think it's pretty hard to downgrade...
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Unread 08-31-2013, 07:41 PM   #4
wgirvine
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Alternators do not put out max amps at idle. If your demand is more than the alternator can output, then the battery takes up the slack... for a little while. But the voltage will drop under heavy demand at idle, that's normal. The more current you demand, the more the voltage will drop.

Also, you need to understand that an alternator has 3 windings, each producing 1/3 of the alternator's rated output. If one winding goes bad (blown diode) the alternator will continue to produce 14 volts, but only 2/3 of the amps. So if you're asking more amps than the alternator can supply, the voltage will drop.

So first, get your alternator tested.
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Unread 09-01-2013, 05:58 AM   #5
biffgnar
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Originally Posted by rage4order View Post
Can't complain for the price I paid. And switching from a bottom-of-the-line Duralast, I think it's pretty hard to downgrade...
I bet that Duralast would live longer than most Optimas these days.
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Unread 09-01-2013, 08:23 AM   #6
rage4order
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Really??? I didn't realize they were THAT bad.
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Unread 09-01-2013, 08:26 AM   #7
rage4order
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Quote:
Originally Posted by wgirvine View Post
Alternators do not put out max amps at idle. If your demand is more than the alternator can output, then the battery takes up the slack... for a little while. But the voltage will drop under heavy demand at idle, that's normal. The more current you demand, the more the voltage will drop.

Also, you need to understand that an alternator has 3 windings, each producing 1/3 of the alternator's rated output. If one winding goes bad (blown diode) the alternator will continue to produce 14 volts, but only 2/3 of the amps. So if you're asking more amps than the alternator can supply, the voltage will drop.

So first, get your alternator tested.
That kind of sounds like my problem. As soon as I turn anything on my volts drop noticably. Even if it's just my headlights.
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