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Old 04-10-2012, 09:22 PM   #1
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Alternator wiring

I am putting a 100 amp GM alternator on my engine and I understand that the (#1) spade terminal must be switched. The question is do you switch it on just to excite the alternator or is it switched on the whole time the engine is running? Thanks. J.T.Duncan
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Old 04-10-2012, 11:16 PM   #2
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I don't think it matters but common practice is to leave it live all the time. I seem to recall a parlour trick from my youth where you could pull the wire off an internally regulated alternator and it would keep charging BICBW.
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Old 04-11-2012, 03:36 AM   #3
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Do a google search on 'delco alternator wiring'. There are lots of examples of the wiring.
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Old 04-11-2012, 06:50 AM   #4
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"I am putting a 100 amp GM alternator on my engine"

Many auto alternators will never create their output , they get warm , and the output dies off.

For planning if it is a small frame unit plan on no more than a 60A charge rate with a 3 stage regulator , far less with internal one wire V reg.

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Old 04-11-2012, 05:36 PM   #5
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New deal, carried the alternator to the repair shop and they are changing the regulator to one that is self exciting, so that is that.
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Old 04-11-2012, 06:50 PM   #6
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We don't know what your application is so this is all speculation but assuming you think you need a bigger alternator because you have some big battery bank to charge, you are doomed to disappointment with any internally regulated alternator, no matter how excited it gets. Re-read what Fred posted earlier and note that his comments were based on a 3-stage EXTERNAL regulator.
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Old 04-12-2012, 05:54 PM   #7
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No big bank, the old one (original) was shot and being the cheap skate that I am, well that explains it all.
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Old 04-13-2012, 07:10 AM   #8
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"and being the cheap skate that I am,"

While the alt was being rebuilt it would cost almost nothing to have the field wire lead out and the internal auto brain V reg tossed in the garbage.

While folks today desire automatic everything the fancy Voltage regulator is not a requirement for a fast recharge.

Way back a wire wound variable resistor and a switch would be used to turn off the V reg and the wire wound would apply the voltage to the alt.

Sure a boiled batt set could happen , but a careful operator could cut the charge times in half , compared to an auto brain V regulator.

"Either one has time or money..."

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Old 04-13-2012, 09:19 AM   #9
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Quote:
Originally Posted by awpptdt View Post
I am putting a 100 amp GM alternator on my engine and I understand that the (#1) spade terminal must be switched. The question is do you switch it on just to excite the alternator or is it switched on the whole time the engine is running? Thanks. J.T.Duncan
You "understand" based on what?

Did this alternator not come with installation instructions? Are you not replacing an existing alternator?

Rather than ask for hit or miss advice on a web forum, I would follow the installation instructions or wire it the way the one you are replacing was wired.

If neither of these are appropriate, I would contact the manufacturer for wiring instructions.
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